--------------------------- 3]EXPANDING YOUR AMIGA 3]By Morton A. Kevelson, P.E. --------------------------- The initial thrill has worn off. You have become comfortable with your new Amiga and have started to get bored running only games. You have decided it's time to get down to some serious work and you are starting to look around for serious applications. It does not take long to find out the stock Amiga 500 -- and even an Amiga 2000 -- have a number of limitations as they come out of their boxes. The amount of disk swapping to be done is the first thing that grabs your attention. A shortage of memory, especially on the Amiga 500, shows up next. It is a fact that 99 percent of guru visits are due to a shortage of memory. The solution to these problems is to expand your system. Expanding with an unlimited budget is simple: Just buy everything in sight. However, most of us must exercise judgement and constraint. The approach to take differs for Amiga 500 and the Amiga 2000. I will first deal with the Amiga 500. Amiga 2000 users should read this section as well, since many of these considerations will apply. The basic Amiga 500 has 512 kilobytes of RAM and a single disk drive. These facilities are at best inconvenient and at worst inadequate for most serious applications. Even games are starting to demand more from the computer. While most games will run on the basic system, some games now require a minimum of one megabyte to run. Many games will also take advantage of additional system resources, such as extra disk drives, when they are available. The first decision will be whether to add memory or disk storage. If at all possible, I strongly recommend that you do both. If your budget is so limited that you cannot possibly do both at the same time, then I suggest you start with a second disk drive. Although many users may disagree, in the absence of specific application considerations this is the approach I would take. The Amiga 500 is pretty much limited to a single external disk drive, though the operating system can actually support up to four. The disk drive limiting factor on the 500 is its power supply. Commodore designed the 500's power supply to handle the computer, its internal memory expansion and one external disk drive. It is also my understanding the latest version of Commodore's own A1010 external disk drive no longer passes through the power lines. If you ever do want to operate the 500 with more than two disk drives, you should consider one of the third-party units, which are self powered. The next expansion step is the internal 512 kilobyte RAM module which plugs into the port beneath the computer. There are two reasons why you should add this memory module, even if you are planning to expand the computer with eight megabytes of external RAM. First of all, the internal memory module comes with a battery backed real time clock. Although the real time clock is not essential, it comes in handy and it is good to have. The second reason is far more compelling. The current Amigas are being shipped with the new, expanded fat Agnus chip. This new Agnus, which is part of the soon-to-be-released enhanced chip set, is able to access a full megabyte of chip RAM. In comparison, the original Amigas could only access 512 kilobytes of chip RAM. I won't go into the details of chip RAM at this time. However, I will say it is important for applications that work with graphics or sound. At this point you will have an Amiga 500 with one megabyte of RAM and two disk drives. This a reasonably functional system, although you may encounter some limitations with graphics applications. Any additional expansion will most likely be via the computer's 86-pin expansion port, which is located on the left side of the machine. The problem with the Amiga 500 is that there is only a single expansion port. If you are not careful, once the port is filled you may unable to install additional devices. Practically speaking, the most effective way to utilize the expansion port on 500 is by adding memory and a hard disk drive as a single module. These are generally self contained units with their own power supply. Some manufacturers offer the power supply as an option. Some of these units, such as the IVS Trumpcard 500, are basically a two-slot expansion chassis with a hard drive controller and a hard drive. The second slot can then be used for additional memory or any other Amiga 2000-style accessory card. Others, such as Commodore's A590, come with the hard drive and chip sockets for two megabytes or more of expansion RAM. There are several advantages to postponing the purchase of the RAM chips. To start, it lets you use your money to buy a larger hard drive without limiting the amount of memory you can add later on. You may wish to consider purchase of a hard drive module without the hard drive. Careful shopping can find a real bargain in large capacity hard disk drives. I recently found the 48-megabyte, Seagate ST157N SCSI drive advertised for less than $350. Just check with the manufacturer of the controller card if the hard drive you intend to buy is supported by the installation software. I personally prefer the use of SCSI-compatible drives as opposed to the more common ST506 variety. Although the ST-506 drives may seem less expensive than a comparable SCSI drive, the Amiga's SCSI controller cards are usually less expensive than the ST-506 controllers. I have also found the price difference for hard drives disappears for the larger sizes. It is also easy to connect up to eight SCSI devices on a single controller card. Just make sure that the module you are considering has an external SCSI connector. Delaying the purchase of memory, even if it is for only a short time, can result in a lower system cost in view of the currently declining memory prices. The newest of user expandable memory boards will accept industry standard SIMM modules. For example, Xetec is presently designing an add-on board for their Fasttrak hard drive system which will accept up to eight megabytes of SIMM modules. SIMMs come in 256 kilobyte or 1 megabyte chunks. The ones that are designed for installation in MS DOS computers come with nine chips to a strip. The ninth chip is used for parity checking. The ones for Macintosh computers use only eight chips. Several stand-alone expansion chassis are available for the Amiga 500. These have two or Amiga 2000 style expansion slots. I suggest caution when considering these devices. The Amiga 500's expansion slot is not a true A2000 style connector. As a result, some A2000 style accessory boards will not work at all or may exhibit compatibility problems when used with other such products. The advice of the manufacturer of the expansion box should be followed when selecting components for installation. A similar word of caution applies to the pass-through connectors provided on some expansion modules. The pass-through connector tries to duplicate the Amiga 500's expansion connector to permit daisy chaining of additional expansion modules. As with the stand-alone expansion boxes, compatibility problems can arise. There are also several technical limitations as to the number of daisy-chained peripherals which can reliably function on the expansion bus. The Amiga 2000 was designed with expansion in mind. Beneath its cover you will find no fewer than five 100-pin Amiga slots, two PC-XT and two PC-AT slots, an 86-pin coprocessor slot, a dedicated video slot and space for a 3 1/2 inch and a 5 1/4 inch disk drive. However, all of this represents only potential hardware. The unexpanded Amiga 2000 is nearly as limited as the Amiga 500. The only operational difference between the two machines is that the Amiga 2000 has a full megabyte of RAM and a built-in battery-backed clock. In fact the 500 is far more cost effective than the 2000 if you limit your expansion to memory and disk drives. As with the 500, you should start your 2000 expansion with disk drives and RAM. Keep in mind that once a drive bay is filled, it cannot be used for anything else. The 5 1/4 inch drive bay was intended for the disk drive which comes with the bridgeboard. Low cost adapters are readily available which let you mount anything from a 3 1/2 inch floppy drive to a 5 1/4 inch hard in the larger drive bay. The 3 1/2 inch drive bay can be filled with a second floppy drive or a hard disk drive. Many users disparage the need for a second floppy drive once a hard drive has been installed. I prefer the convenience of having a second disk drive, though a hard drive lets you run application software without additional floppies. A second disk drive simplifies the routine tasks of moving files and copying disks and in the long run will save much time. A second drive also makes it easy to try new software before it is installed on the hard drive. The 2000 also has a disk drive port on the back panel. Keep in mind that a disk drive connected to the back port appears to the system as device df2:. This can cause problems with some programs. Most hard drive controllers can now be configured as hard cards leaving the drive bays available for other devices. In most cases, a hard card will have to be installed in the rightmost expansion slot to avoid conflicts with the adjacent slots. Note that a hardcard so installed may ultimately interfere with an accelerator card which is installed in the coprocessor slot. Although compatibility among Amiga 2000-style accessory cards has generally been good, the possibility of interference between devices from different manufacturers still exists. Always try to arrange for a trial period when you are adding devices to your system. Most manufacturers are usually willing to let you know of any compatibility problems they may have encountered with competing devices. Additional RAM should be high on your shopping list. Most applications, with the possible exception of animations, run comfortably in three megabytes. Nevertheless, I suggest you look at those memory boards which can accommodate a full eight megabytes. You can buy these boards with enough RAM for your present needs and add the rest according to the dictates of your budget and computational requirements. Accelerator boards are becoming more popular as their price starts to drop. These add a full 32-bit microprocessor to the system, such as the 68020 or the 68030, which usually run at a faster clock speed as well. Some of these boards are also equipped with a quantity of 32-bit RAM. Keep in mind that not all software can take advantage of the extra processing power which is offered by these devices. One thing you should not have to worry about with the Amiga 2000 is lack of power. Its 200-watt power supply should be more than adequate for anything you can stick inside the box. Though the Amiga 2000 offers plenty of room for expansion, it still pays to plan ahead. Careful planning, based upon your needs, can improve the efficiency of your system and reduce your expenditures. Read the reviews and respond to the ads for manufacturers specifications. Try to find other users who already use out some of the products you may be contemplating. In the end your efforts will be well rewarded. 4]END OF TEXT