Data Sharing
Introduction
This chapter explains the use of the data sharing tools which are included with Amiga Forever. Some more general issues related to sharing data between Amiga and other systems are also discussed. An Amiga-specific reference version of the instructions for using the software is included in the "ReadMe.txt" file on the Amiga Forever floppy disk.
The Amiga Forever floppy disk is provided for users who do not have a CD-ROM drive on their Amiga. The disk contains the parts of Amiga Forever which are designed to run on a "real" Amiga computer, including the Amiga Explorer network server software (to connect one or more PCs to the Amiga) and the MSH filing system (to read and write MS-DOS disks on an Amiga).
The floppy disk also contains the "transdisk" and "transrom" utilities, used by several Amiga emulation environments. These utilities are not necessary if Amiga Explorer is installed, because Amiga Explorer incorporates and extends the features of both tools. Amiga Explorer and MSH are fully independent from the Amiga emulation software, and can be used to share data between Windows and Amiga systems without using the Amiga emulation software.
All Amiga software included on the Amiga Forever floppy disk is designed to run on version 1.3 and upwards of the Amiga OS. Some programs may even work on older versions.
A copy of the Amiga Forever floppy disk is included on the CD-ROM, in the "Amiga/AF_Disk" directory. The disk is also stored in the DMS and LhA formats, inside the "Archives/AF_Disk" directory. If the floppy disk was not physically included with a specific distribution of Amiga Forever, it can always be created on an Amiga with a CD-ROM drive, or on an Amiga capable of reading PC disks (by first copying the DMS or the LhA file to a DOS-formatted 720 KB floppy disk).
The AmiToRTF software, which is a conversion tool between Amiga and Windows text formats, is described in the chapter dealing specifically with the Amiga software included with Amiga Forever.
Up and Running in 1 Minute (Amiga Explorer and MSH)
If it is sufficient to use the Amiga Explorer functionality over a null modem serial cable connection, and/or the MSH filing system to access MS-DOS (or IBM PC DOS) disks on the Amiga, then it is possible to entirely skip all configuration steps described in this chapter, and simply boot the Amiga from the Amiga Explorer floppy disk, and then remove the disk. This does not even require a monitor to be connected to the Amiga. Such a configuration is most useful if the Amiga is only used as an "Amiga floppy drive" for the Windows computer.
If the floppy disk was created manually by formatting a disk and copying the Amiga Forever floppy disk files from the CD-ROM, it may occur that the Amiga does not boot from that disk. If this is the case, the disk should be made bootable by inserting it in the Amiga's drive 0, and running the command "DF0:c/Install DF0:" from an Amiga CLI or Shell window.
To run Amiga Explorer on the Windows side it is only necessary to install the software (running the installation program, or as described in the Amiga Explorer section), and to make sure that the proper COM port is selected (right-click on the Amiga Computer icon on the Desktop, then "Properties") for communications with the Amiga. If Amiga Explorer does not run as described here, it is possible that an incorrectly wired serial cable is being used. For more information, please refer to the full sections about Amiga Explorer and serial cables.
Amiga Explorer
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Amiga Explorer Sample Screen |
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Amiga Explorer is a networking software which allows any number of Windows systems to access the resources of an Amiga computer. The computers may be physically connected with a "null modem" serial cable, or via TCP/IP.
The Amiga side of Amiga Explorer communicates with the Amiga Explorer part which resides on a Windows computer, exposing all Amiga drives to one or more PCs running Windows. In this configuration, the Amiga is called the "server", because it is the computer which satisfies requests from "clients", which are Windows machines. All Windows clients can "see" what is on the Amiga server, and read and write to the Amiga from the Windows Desktop. The Amiga itself does not see the drives mounted on the client machines, i.e. the drives of the Windows computers do not appear on the Workbench screen of the Amiga server.
The Windows side of Amiga Explorer is installed automatically (if so desired) by the Amiga Forever installation program. Amiga Explorer can also be installed manually, with a right-click on the "Windows/AExplore/AExplore.inf" icon on the CD-ROM, and selecting "Install". Under Windows 95, the system must be restarted for the "Amiga Computer" icon to appear on the Desktop and for the software to start working. Under Windows 98 and NT, a reboot is never required, but a logoff/logon is necessary if an older version of the software was already in use during the installation. For security reasons, on Windows NT it is required that system extensions like Amiga Explorer be installed by a user having administrator privileges. If the account used to log on to the system does not have administrator rights, the installation will fail. The Windows NT default user account has administrator privileges, but especially in larger organizations administrative tasks are not performed by regular users, so different types of accounts may be set up.
On the Amiga side, a double-click on the "AExplorer" icon is sufficient to start it, and, if necessary, to stop it. Stopping Amiga Explorer may be useful, for example, to free the serial port for other tasks, or to change some Amiga Explorer settings. To install Amiga Explorer, it is sufficient to copy the "AExplorer" icon to the hard disk. On version 2.0 and newer of the Amiga OS, copying the "AExplorer" icon into the "WBStartup" drawer will cause Amiga Explorer to start automatically when the system boots (note: if TCP/IP is used as the protocol, then TCP/IP must be started before Amiga Explorer). On all Amiga systems, Amiga Explorer can also be started automatically by entering the following line in the "S:Startup-Sequence" or "S:User-Startup" file:
Run >NIL: <NIL: AF_Disk:AExplorer >NIL: <NIL: [OPTIONS]
"AF_Disk:", which in this example is the path for the Amiga Forever floppy disk, should be replaced with the path of the software as it is installed on the hard disk, e.g. "Work:", or "Work:AmigaForever/", etc. The optional [OPTIONS] part consists of one or more keywords each followed by a setting, e.g. "CONNECTION SERIAL SERBAUD 115200", etc. If no options are indicated, then the default settings are used. All command line options have the same name as the matching ToolTypes.
On the Windows side, once the "Amiga Computer" icon is displayed on the Desktop, the configuration dialog box can be displayed by selecting "Properties" after a right-click on the icon. It is very important that Amiga Explorer be configured to use the correct port and connection to the Amiga computer, or otherwise the two sides will not be able to communicate.
On the Amiga side, the Amiga Explorer settings can be changed by clicking on the "AExplorer" icon once, and selecting the "Information..." (or "Info", on older systems) item from the Workbench menus. All settings are accessible by editing the corresponding "ToolType" entries. The "CONNECTION" entry may be set to AUTO, SERIAL or TCP/IP. AUTO, which is the default, means that Amiga Explorer uses TCP/IP if a TCP/IP environment is found, otherwise it uses the serial (null modem) cable connection.
For additional information on the connection types and the related settings, please refer to sections describing the serial and TCP/IP connections.
Both the Windows and the Amiga side of the software additionally have settings to change some secondary options of Amiga Explorer.
The Packet Size ("PACKETSIZE" ToolType on the Amiga side) value indicates the maximum size, in bytes, of the data packets sent by the computer on which the software is configured to the other side. A "packet" is the unit of data which is transmitted from one side to the other at one time. Each packet has different checksums to ensure the integrity of the data, once the packet is received by the other side. If the line is not totally error-free, which may for example occur on a serial connection which is set to an excessively high speed, corrupt packets are detected and re-sent. If this happens, the overhead is in proportion to the size of the packet. Longer packets are more likely to be corrupt, because they contain more data, and they also take longer to be sent and re-sent. Shorter packets are more reliable, but they slightly increase the overall overhead on an error-free line, because each packet has some additional header and checksum data, which, if there are no errors, is not necessary. By default, the packet size is set to 4096 bytes, which is a good compromise for different types of connections. It is not necessary to set the Amiga side and the Windows side to the same value. All Amiga Explorer packets are "dynamic", i.e. the packet size is only a maximum, not a constant. If the packet size is set to 4096, but only 100 bytes need to be transmitted, then only 100 bytes (plus the header) are transmitted.
The Max Retries ("RETRIES" ToolType on the Amiga) parameter determines how often the software will request a corrupt packet to be retransmitted by the other side, before "giving up". By default, it retries 10 times. The Amiga and the Windows side do not need to be set to the same value.
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Amiga Explorer has two specific settings to enable logging, which in case of persistent difficulties can be a great aid to better track the origin of specific problems. By default, logging is disabled. On the Amiga side, logging is enabled using the "LOGGING" and "LOGFILE" ToolTypes. Similarly, the Windows has an Enable Logging option, and the possibility to specify the path and file name of the logging file. Since log files can grow very large, it is recommended to start with an empty or new log file, and specifically log only those actions which are causing a problem (e.g. the copy of a specific file, or opening a certain directory). From a privacy perspective, it should be noted that the log files may contain small references to the beginning and end of the contents of the files that are transferred.
The Amiga side of Amiga Explorer has four additional settings, controlled by the "ADFVERIFY", "OVERRIDEPROTECTION", "QUIET" and "DONOTWAIT" ToolTypes. These have no equivalent on the Windows side.
"ADFVERIFY": Amiga Explorer can transform Amiga disks to ADF ("Amiga Disk File") images, and vice versa; when writing an ADF image to an Amiga disk, Amiga Explorer by default verifies that the data was written correctly, just like the Amiga OS does when formatting a disk, or like disk-copying programs can do during a copy. In this way, bad disks and other possible problems are immediately detected. If ADFVERIFY is set to NO, bad disks and other write errors are not detected, but the write process will be faster.
"OVERRIDEPROTECTION": If this setting is enabled (=YES), then Amiga Explorer overrides any Amiga protection bits which may indicate, for example, that a file cannot be deleted, read or written.
"QUIET": This setting can be set to YES or NO to respectively suppress or enable the initial and final status window which appears when Amiga Explorer is launched or stopped.
"DONOTWAIT": This ToolType ensures that the "AExplorer" icon can be dropped in "WBStartup" without leaving the Amiga OS waiting for Amiga Explorer to terminate.
Using Amiga Explorer is as simple as using the normal Windows Desktop. Amiga disks and files become accessible on the Desktop, and can be read, copied, moved, renamed, etc. A right-click on any of the items contained in an Amiga Explorer window exposes the different functions which are available, e.g. Properties, Format, etc. Drag-and-drop to and from other programs is also possible, if the applications support it (Amiga Explorer gives applications streaming access to Amiga data, but not random access, so the application must support streaming access to files). Additionally, Amiga Explorer creates and makes accessible virtual ROM image and ADF disk image files, which are most useful in combination with Amiga emulation programs. Each Amiga floppy disk can be accessed as a normal volume, or using the associated ADF image file (also see the section on floppy disks and that about the transdisk tool), which is generated automatically by Amiga Explorer. Dragging an existing ADF file (for example from a hard disk on the PC, or even from the Amiga) and dropping it on one of the ADF files created by Amiga Explorer for each drive will write the ADF image to the corresponding floppy drive.
Serial Cables and Configuration
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A serial cable connection is a standard and inexpensive method to connect different types of computers and other communications devices. While it is not the fastest type of cabling for networking, it is probably the simplest to implement on the most different systems. To connect two computers, for example an Amiga and a PC, it is necessary to use a "null modem" serial cable. For technical details regarding serial cables and connectors, including in particular different types and lengths of null modem cables, please refer to the chapter dedicated to null modem serial cables.
Null modem connections can be used directly by Amiga Explorer, as well as by terminal programs, and even by TCP/IP, to transmit data from one device to the other. Amiga Explorer accesses the serial devices directly, without requiring any terminal or TCP/IP software.
PCs usually have at least two serial ports, named COM1 and COM2. Serial ports can operate at different speeds. Higher speeds have the potential to be less reliable. The Windows side of Amiga Explorer needs to be configured by the user to the correct port i.e. the port to which the Amiga computer is connected), at the correct speed (the same speed set on the Amiga side).
The most common causes of problems when using Amiga Explorer over a serial connection are:
- Incorrect COM port selected on the Windows side
- Speed too high, or not set to the same value on Windows and the Amiga
- Incorrect wiring of the null modem cable
The following paragraphs, as well as the chapter about null modem serial cables, explain how to configure Amiga Explorer, avoiding these potential difficulties.
As explained for Amiga Explorer in general, the Windows side of the software is configured by selecting Properties after a right-click on the Amiga Computer icon, whereas the Amiga side is configured by editing the ToolTypes associated to the Amiga Explorer Workbench icon.
The Amiga side does in general not require initial configuration, because the Amiga has only one serial port, which is preselected. Likewise, a connection speed of 19.2 kbit/sec is already preset to be the same as on the Windows side.
On the Windows side, after the correct COM port has been selected, the transmission speed can be set by clicking on "Settings..." The standard system dialog box for setting the properties of the COM port includes several different parameters, but Amiga Explorer only requires the proper speed setting. All other values are set automatically by Amiga Explorer. By default, both the Amiga side and the Windows side of Amiga Explorer are preset to 19200 bits per second (19.2 kbit/sec). We recommend to first test Amiga Explorer with these settings, and then to try and increase the speed, if necessary. When the speed is changed, the new value must be set on both the Windows side and the Amiga side.
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A speed of 19.2 kbit/sec was tested to work well under all Amiga configurations, even with an original 68000 CPU. Settings of 38.4 kbit/sec have been successfully tested on Amiga 1200 systems (68020 CPU), while Amiga 3000 and 4000 systems (68030 and higher CPUs) worked flawlessly at speeds up to 115.2 kbit/sec, using the standard Amiga serial port and the standard Amiga serial.device.
The performance of the Amiga serial port may be reduced depending on the screen resolution and depth. On AGA systems, this is most noticeable with eight-bitplane screens (256 colors), while in OCS/ECS (Original/Enhanced Chip Set) Amiga systems, "High Res" screen modes with 16 colors (four bitplanes) or more may already cause disruptions. This means, for example, that Amiga Explorer may work properly at 115.2 kbit/sec, until a screen with 256 colors is brought to the front, at which all transfers will suddenly fail. To correct this, try to limit either the serial connection speed or the depth of the screen displayed during the transfer.
If the software is configured properly, any problems that may be experienced are most likely to be in relation with improperly wired serial cables, which may in some cases even seem to work well at some speeds, or with small amounts of data, but which may then produce errors under more demanding conditions. Please refer to the section on serial cables for additional information.
On the Amiga side, "SERDEVICE", "SERUNIT", "SERBAUD" are the ToolTypes for the serial port settings. By default, the standard Amiga serial device, "serial.device", unit 0, is used. This does not require changes, unless non-standard serial ports and devices are used, in which case the manufacturer's documentation needs to be referred to. As on the Windows side, on the Amiga SERBAUD is preset to 19200 bit/sec.
The Windows side of Amiga Explorer only uses the PC's serial port while a data transfer is in progress. At all other times, the serial port is available for other programs to use. Since the Amiga has to act as a server, which means "listening" all the time for requests from clients, the Amiga serial port is kept busy all the time. It is possible to temporarily free the Amiga serial port by double-clicking on the "AExplorer" icon to stop Amiga Explorer, and then re-start it again, as necessary.
TCP/IP
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Amiga Explorer can use the TCP/IP protocol, if both the Amiga and the PC in which Amiga Explorer is installed have TCP/IP installed and running. TCP/IP is the software protocol normally used with Ethernet boards, which have become relatively common and inexpensive both for PCs and for Amiga systems. While serial connections usually do not exceed theoretical speeds of 115.2 kbit/sec, Ethernet speeds start at 10 mbit/sec (10 million bits per second).
Compared to other networking tools which rely on TCP/IP, Amiga Explorer couldn't probably be easier to install, since it only requires the Amiga's IP address to be set in the Windows side of the software. The Amiga side automatically detects a TCP/IP environment and starts listening to requests from Windows clients, without any configuration at all. Additional security measures are possible to prevent unauthorized computers from accessing data on the Amiga. In any case, setup should not take more than a few minutes.
The installation of Ethernet boards, cabling and TCP/IP is outside the scope of this documentation, since these products are usually supplied with full documentation. However, we would like to include some short notes and recommendations, in case you don't have Ethernet or TCP/IP installed yet, and have no experience in this field.
Ethernet comes in different speeds and cable types. PC Ethernet boards are available in 10 Mbit/sec and 100 Mbit/sec ("Fast Ethernet") speeds. Amiga boards usually only support 10 Mbit/sec Ethernet. The most common types of wiring are 10Base-2 (also called "Thin Ethernet", or "Cheapernet", with reference to an older standard), which is a single, continuous coaxial cable which connects all computers, and has terminators on both sides, and 10Base-T, which is an 8-wire telephone-like cable with RJ-45 plugs on both ends. 10Base-T requires a device called a "hub" if more than two computers are to be connected. If a hub is used, all computers have wires going to the hub. For two computers only, a special type of 10Base-T cable, with some wires crossed in a way similar to null modem serial cables, can be used. A standard 10Base-T cable will not work to connect two computers, but can only connect a computer with a hub. The most common cause of Ethernet problems are incorrectly-wired or terminated cables. Even if the correct connections are made, but the wrong pairs of wires are twisted, a cable may work over short distances, but fail at longer distances. For this reason, it is recommended to purchase readily-assembled Ethernet cables, especially for a simple network configuration. If a 10Base-2 cable is used, it is also important to plug a terminator at each of the two ends. Fast Ethernet in general does not support 10Base-2 (coaxial cable), but only 100Base-T, which uses the same RJ connectors and number of wires as 10Base-T, only it has higher-quality requirements. The quality required for 100 Mbit/sec is often referred to as "Category 5" wiring. "UTP" indicates unshielded Base-T cables, while "STP" refers to the version in which each twisted pair has its own shielding. "TP" stands for "twisted pair", meaning that wires are twisted pairwise to reduce interference. Both UTP and STP are also available in "S/UTP" and "S/STP" versions, where the "S" stands for "screened", meaning that the entire cable has an additional external shielding layer. Category 5 STP (and S/STP) cables are slightly more expensive than the other combinations, but are probably the most reliable and open to future upgrades. Most 10 Mbit/sec Ethernet boards support both 10Base-2 and 10Base-T cables. Most 100 Mbit/sec boards can also transmit and receive at 10 Mbit/sec (so called "10/100" boards"), but do not support coaxial cables (10Base-2). Before deciding, it is good to consider what types of cables the Amiga and the PC Ethernet boards support, and whether it is appropriate to make a longer-term investment by purchasing a 10/100 board for the PC.
TCP/IP comes standard under Windows, but is a separate product on the Amiga. Amiga TCP/IP packages include "AmiTCP/IP", and "Miami". Some of these are available for free download on networks like the Aminet, although in some cases they may provide only limited functionality unless they are registered or purchased at a fee. If TCP/IP is not already installed in Windows, it can be added from the Control Panel (Network properties), adding TCP/IP, which appears is in the list of protocols directly supported by Microsoft.
TCP/IP can be complex to install, but this does not need to be, especially if it is only required for running Amiga Explorer. With TCP/IP, each computer in a network is assigned a different IP address. IP addresses can be "public" (i.e. unique worldwide), in which case they are assigned by an Internet registration authority, or "private" (i.e. still unique, but only on the local network). IP addresses in the format 10.x.x.x are reserved for private (local) addressing. An additional parameter, called "network mask", is used to organize larger networks into subnets. For a simple private network, with up to 254 computers, the addresses could be assigned in the range from 10.0.0.1 to 10.0.0.254 (the addresses 0 and 255 are reserved), with the network mask set to 255.255.255.0. For example, the PC could be assigned the IP address 10.0.0.1, and the Amiga could have the IP address 10.0.0.2.
Both the Amiga and the Windows side of Amiga Explorer also support host name addressing (e.g. "computername.domain.com"), in addition to numerical IP addresses (e.g. "10.0.0.1"). On a network which dynamically assigns IP addresses to computers, for example using a DCHP server, each computer does not have a constant IP address, but instead may be reassigned a new and different address each time the machine is switched on. In this case, the computer has a "host name", which remains constant, and which can be set in Amiga Explorer where the IP address is normally set. The use of host names is also possible on simpler configurations, but it is not the default method proposed for Amiga Explorer because it may require additional TCP/IP configuration steps to make sure that host names are properly mapped to IP addresses, which is normally done by at least one computer that acts as a DNS server (where "DNS" comes from "Domain Name System").
The most common utility used to verify the functionality of TCP/IP is the "ping" command, which is included in most versions of TCP/IP on different platforms. The "ping" command sends a test packet to a certain IP address, and waits for it to be sent back, resulting either in an error message or a success confirmation. For example, if the Amiga is 10.0.0.2, and the PC is 10.0.0.1, typing "ping 10.0.0.1" in the Amiga Shell will verify if the connection with the PC works. On the PC, typing "ping 10.0.0.2" will confirm that things also work in the opposite direction. In a configuration like this, the PC side of Amiga Explorer needs to be configured to talk to the IP address 10.0.0.2, which is the Amiga. The Amiga automatically replies to the address from which it receives a request, so it does not need to be configured with the PC's address.
On more complex networks, software and hardware tools like firewalls, proxy servers and routers may be installed, which may require some additional configuration steps. Organizations with these networks usually have a network administrator, who will be able to help if there are problems. On these configurations, it may be useful to know that Amiga Explorer uses "port 356" to transmit and receive its data, and that security features based both on password and on IP address can be set in Amiga Explorer.
When Amiga Explorer starts on a computer which also hosts a proxy client, the proxy software may try to connect to the proxy server computer, to see if it knows where the Amiga address is. If the connection requires a telephone call, as is the case in proxy configurations used for Internet access, this can add unnecessary delays and expenses, in which case it is best to explicitly disable the proxy client for port 356.
The most common causes of problems when using Amiga Explorer over a TCP/IP connection are:
- TCP/IP not installed correctly (PC and Amiga cannot "ping" to each other at the addresses specified in Amiga Explorer)
- Firewall, proxy server or router between PC and Amiga do not relay data on port 356, used by Amiga Explorer
- Attempt to start Amiga Explorer (e.g. in Amiga "Startup-Sequence", or "WBStartup") when TCP/IP is not yet running on the same machine
Once TCP/IP works properly, the Windows side of Amiga Explorer can be configured by selecting Properties after a right-click on the Amiga Computer icon, whereas the Amiga side is configured by editing the ToolTypes associated to the Amiga Explorer Workbench icon (as explained for Amiga Explorer in general).
When TCP/IP is selected as the protocol on the Amiga side, it is additionally necessary to click on "Settings..." to specify at least the IP address of the Amiga computer. The address is typically represented in dotted-decimal notation (as in "10.0.0.2"). It is also recommended to change the password, which by default is preset to the same value both on the Amiga and on the Windows side. If the password is not changed, and the Amiga is connected to the Internet, for example, then intruders may - in theory - access the Amiga resources using the default Amiga Explorer password. When the password is changed, the new value must be set both on the Windows clients and on the Amiga server.
The TCP/IP settings on the Amiga side ("TCPLIBRARY", "TCPPASSWORD", "TCPCLIENT", "TCPSERVER" ToolTypes) by default do not require any specific configuration. The Amiga side of Amiga Explorer processes requests from all Windows clients. To limit potential security risks, Amiga Explorer gives the possibility to specify not only a password (TCPPASSWORD), but also to indicate the IP address of a single Windows client to which exclusive access is to be granted. This is done by setting the TCPCLIENT parameter to the IP address (e.g. "TCPCLIENT=10.0.0.1") of a single Windows client, which will then become the only client with which the Amiga server exchanges data. This provides an additional level of protection over the password solution, because the (encrypted) password is transmitted over the network, and, in theory, could be read by an unauthorized party on the same network path using a TCP/IP packet monitor. The TCPSERVER setting, which is also optional, can be programmed to the IP address of the Amiga server. This is required on multi-homed systems, i.e. where the Amiga has more than one network board and/or IP address, and Amiga Explorer may need to be told which one to use.
Floppy Disks
One of the most frequently asked questions regarding Amiga and PC data sharing is whether Amiga floppy disks can be read on the PC. This is only possible with the addition of dedicated hardware, like a special floppy disk controller card mounted inside the PC, or a similar interface connected to the PC's parallel port.
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Amiga Explorer makes it possible to connect an inexpensive Amiga (e.g. an otherwise unused A500) to the PC, and to use that as a "floppy drive" to access Amiga data from the PC. This configuration does not even require a monitor for the Amiga.
Unlike the PC, which by default cannot access Amiga disks, the Amiga, which has a more versatile floppy disk hardware than most PCs, can read and write floppy disks in the PC's "DOS" format. On Amiga computers with version 2.1 or higher of the Amiga OS, the CrossDOS filing system is included, providing access to PC-formatted floppy disks and hard drives. If not already installed, CrossDOS can easily be set up by moving the "PC0" and "PC1" icons from the "Storage/DOSDrivers" directory (in the "Extras" disk, on systems without hard drive) to the "Devs/DOSDrivers" directory, to respectively activate support for DOS disks on floppy disk drives 0 and 1. Amiga Forever includes the MSH filing system, which, in a way similar to CrossDOS, allows users of all Amiga operating systems from version 1.2 upwards to read and write MS-DOS floppy and hard disks, which can then be used to share data with PC systems. Neither CrossDOS nor MSH currently support Windows "long" file names, which means that on the Amiga all files and directories, although perfectly readable, appear with a name having a maximum length of eight characters, plus a three-character suffix.
The two most common types of floppy disks used on the Amiga and on the PC are DD ("double density") and HD ("high density"). HD disks can be recognized for having an additional hole in the disk case, on the opposite side of the write-protect tab. DD disks can store up to 1 Mbyte, whereas HD disks can store up to 2 Mbytes (unformatted). After formatting, the net capacity available for user data is lower. This is due to the data structures which are required to organize the disk contents, and to detect medium errors, for example. On the Amiga, DD disks can be formatted to 880 Kbytes, while DOS-formatted disks have a capacity of only 720 Kbytes. HD disks can hold twice the data of DD disks, i.e. 1.76 Mbytes on the Amiga, and 1.44 Mbytes using the DOS formatting. Variations are also possible within the same system, for example the Amiga's Original Filing System (OFS) has a more redundant data structure than the newer Fast Filing System (FFS), which results in a small difference in capacity, so that DD disks formatted with the Amiga OFS can actually only contain a maximum of 838 Kbytes of user data, and not 880 as when the FFS is used. Some non-standard Amiga and PC filing systems further exploit these techniques by providing even higher usable capacities on floppy disks, but at the price of incompatibility with standards, and, in most cases, reduced possibilities for error-recovery.
The Amiga disk controller and filing system were developed after the PC's, and this is in part reflected by the Amiga's higher storage capacity for floppy disks, and the ability to read both Amiga and PC disks. However, when HD disks appeared on the market, it was too late to change the Amiga custom chips to support the double density, which required reading twice the data for each disk rotation. This problem was solved by introducing special Amiga HD drives which could spin at half the standard speed, allowing the Amiga drive controller to handle the data as if it came from DD disks. These floppy drives were mounted on the last generations of the Amiga 3000 and 3000T, shortly before the Amiga 4000 and 1200 were launched, which also used these drives. After the Commodore bankruptcy, it became more and more difficult and expensive to manufacture the non-standard HD drives required by the Amiga. For this reason, the Amiga 4000 and 1200 were again manufactured using DD drives. With the increased diffusion of HD drives compared to DD drives in the PC world, it is becoming increasingly difficult to find DD disks and drives at competitive prices and at high volumes. In many cases, HD disks and drives cost less and are more readily available than the corresponding DD items.
DD disks remain a universally accepted medium to exchange data not only between Amiga computers, but also between Amiga and PC systems. All Amiga computers can read DD disks, and by simply installing the CrossDOS or MSH software, 720 KB PC disks can be read and written to on any Amiga. Some Amiga computers can read both HD and DD disks, in which case HD disks can be used to share 1.44 MB disks with PCs. On Amiga DD drives, and on PC HD and DD drives, HD disks can also be formatted as if they were DD disks, i.e. in the 880 KB or 720 KB formats. Not all Amiga HD drives, however, can read HD disks formatted at 880/720 KB. This is because many Amiga HD drives use the second hole on the disk to automatically activate the half-speed mode, which results in only being able to access the higher density data.
With the inclusion of the Amiga Explorer and MSH software, Amiga Forever gives access to all the known software techniques to read and write floppy disks of both systems. Additional hardware interfaces give PCs to read-only, and in some cases read/wrote access to Amiga disks. At the time Amiga Forever is being released, however, software support for these devices is not so refined as to allow, for example, Amiga disks to be read directly from within the emulation environment, or from the Windows Explorer.
Two hardware solutions are known to be able to connect Amiga drives to the PC. One is the "Catweasel" floppy controller, by Individual Computers, which is an 8-bit ISA board (to be mounted inside the PC) to which the disk drive can be connected. The other device is called "Amiga Floppy Reader" (AFR), is designed by Marco Veneri, and is an interface which can connect an external Amiga floppy disk to the PC's parallel port. The AFR project documentation is included in the "Archives/AFR" directory on the Amiga Forever CD-ROM. If you are interested in reading it, please consider that a newer version may be available on the Internet (see the links below), and that this project is experimental, i.e. it is not guaranteed to work on all possible configurations, and it might even damage the equipment to which it is connected (for more information, please refer to the Legal Notes).
Other solutions are known to be in development to provide at least read-access to Amiga disks through an interface on the PC's parallel port. Symantec in the USA used to manufacture a controller card providing capabilities similar to the Catweasel's, but this is no longer in production.
Amiga emulation programs like UAE and Fellow use "disk
images" of Amiga floppy disks. The most used file format used for these images is
called "ADF" (from "Amiga Disk File"). Each Amiga floppy disk can be
stored in an ADF file (or split in more than one ADF file). ADF files can be created on an
Amiga with a tool like "transdisk", or they can be
created on the fly by Amiga Explorer. ADF files only support
standard Amiga floppy disks, but not certain non-standard "copy protection"
schemes, which in part also fail on different types of floppy drives.
Related sites (Internet links):
MSH
The "MSH" directory on the Amiga Forever floppy disk ("Amiga/AF_Disk/MSH" directory on the CD-ROM) contains MSH, an Amiga file system handler that allows the Amiga to read and write floppy disks in the MS-DOS format, as already introduced in the section on floppy disks. MSH is included in the Amiga Forever floppy disk both in a preinstalled format and in a slightly edited version of the normal distribution, adapted to fit on the floppy disk. The full and original MSH archive (with source code) is stored in the "Archives/MSH" directory on the CD-ROM.
Amiga operating systems beginning from version 2.1 already include CrossDOS, which provides a similar type of support for MS-DOS disks, as explained in the Amiga documentation and in the section dedicated to floppy disks. MSH works on all versions of the Amiga OS, including 1.2, 1.3 and 2.0, without requiring CrossDOS.
To install MSH from the Amiga Forever floppy disk to your system, execute the following in a Shell or CLI window:
Copy AF_Disk:devs/messydisk.device DEVS: CLONE Copy AF_Disk:devs/MountList.MSH DEVS: CLONE Copy AF_Disk:l/MessyFileSystem L: CLONE
In the "S:Startup-Sequence" or "S:User-Startup" file, add one entry for each disk drive for which you wish to enable MSH, where the name of the device to be mounted is "MS" plus the unit number. For example, to add MS-DOS-support to drives 0 and 1, add:
Mount MS0: FROM DEVS:MountList.MSH Mount MS1: FROM DEVS:MountList.MSH
High density data (e.g. HD disks formatted for 1.44 MB) cannot be accessed by the Amiga unless the Amiga drive is of HD type (not DD, which is limited to the 880/720 KB formats). Some drives shipping with the Commodore Amiga 3000, 3000T, 4000 and 1200 models, as well as some newer third-party drives support this. If high-density is not supported by the drive, then only disks formatted in the 720 KB format can be accessed by the Amiga. Also, some Amiga HD drives can only access HD disks if these are formatted in a high density format. To avoid potential incompatibilities, 880/720 KB formats are best used only on DD disks, and not with HD disks.
Related document (local link):
Other Tools
The "Trans_Disk+ROM" directory on the Amiga Forever floppy disk ("Amiga/AF_Disk/MSH" directory on the CD-ROM) contains the "transdisk" and "transrom" utilities, which can be used to create image files of Amiga ROMs and floppy disks (ADF format), for use with the UAE and Fellow Amiga emulators. The same functionality is also part of Amiga Explorer, which is the recommended data transfer tool under Amiga Forever, and which is capable of creating "virtual" ADF and ROM image files, so these additional tools are mainly interesting when Amiga Explorer is not used.
Both utilities are designed to be used from the Shell. Before use, they are best copied to the C: directory, or to another location where the system looks for programs associated to Shell commands. Transdisk and transrom are best not run without other command line options or redirection commands, because simply typing "transdisk" or "transrom" will cause the programs to start running, sending all program output (i.e. several 100 Kbytes of data) to the CLI or Shell. Please refer to the Amiga DOS and Shell documentation for additional information on the ">" output redirection command, which is shown in practical use here.
The following are examples of command lines entered in a Shell (or CLI, on older systems) window.
To install the command line utilities:
Copy AF_Disk:Trans_Disk+ROM C: CLONE
To get instructions on the use of transdisk:
transdisk ?
To create a disk image of the disk in drive 0, and save it in RAM:
transdisk >RAM:df0.adf
To create (write) a floppy disk in drive 0 from an existing ADF file stored in the Work partition:
transdisk -w Work:disk.adf
To write a ROM image file to the PC0: MS-DOS disk:
transrom > PC0:kick31.rom
To write a ROM image file to the MS0: MS-DOS disk:
transrom > MS0:kick31.rom
Note: transrom, like Amiga Explorer, makes it possible to upgrade the Amiga Forever emulation environment to newer operating system versions (e.g. v. 3.1, or v. 3.5), compared to the ones provided with Amiga Forever (v. 1.0 to v. 3.0). Before using transrom or Amiga Explorer to copy or move Amiga ROMs, please refer to the license agreement which was included with the Amiga OS/ROM being transferred, to make sure that the transfer and the use of these Amiga resources occurs in compliance with the license.
In order to share data created by transdisk and transrom with other systems, if Amiga Explorer cannot be used, it is best to either use floppy disks in the PC's DOS format, or a terminal program with a protocol such as ZModem.
When using PC-formatted floppy disks, the ideal condition is to have an Amiga with a HD drive, which can format HD disks to hold up to 1.44 Mbytes, which is sufficient to store a full, uncompressed Amiga ROM or disk image.
An Amiga ROM image also fits on a 720 KB disk, but a disk image of an 880 KB Amiga disk cannot fit on a 720 KB disk unless it is either compressed (with a program such as LhA), or split in several parts.
The transdisk utility includes an option to split a disk image in several files. For example:
transdisk >RAM:df0a.adf -s 0 -e 39 transdisk >RAM:df0b.adf -s 40 -e 79
will result in two partial disk images which fit on a 720 KB disk. "df0a.adf" contains tracks 0 to 39, while "df0b.adf" contains tracks 40 to 79 (the last track on standard Amiga floppy disks). On Amiga systems with only one floppy drive and very little RAM, it may be necessary to split ADF image files in even smaller sections, e.g. 20 tracks each.
Different operating systems have different system tools and options to append or join the separate ADF files into a single file. Please refer to the respective instructions for additional information. Under DOS and Windows, this can be done with the following command:
copy /b df0a.adf+df0b.adf df0.adf
(the /b option is required to indicate that the files are of "binary" type, and not ASCII text).