DOCUMENTATION LAYOUT V 2.0 ============================= I added two multiplexer to switch between 7 and 14 MHz. This was necessary because some software had problems at 14 MHz (e.g. Janus.library). The multiplexers I use has four channels with each two inputs and one output. Five signals (\VMA, \VPA, E-CLK, \DTACK and CLK) must be switched. So we need two multiplexers. The multiplexer MUST! be a fast (F) type, otherwise the gate delay is be too long. Here's how I connected it : 16 15 14 13 12 11 10 9 | | | | | | | | |-------------------------------------------------------------------------| | +5V EN \DTACK \DTACK \DTACK CLK CLK CLK | | original sync out 7MHz 14MHz out | | | | 74 F 157 | | | | \VPA \VPA \VPA E-CLK E-CLK E-CLK | | SEL original sync out original DIV 2 out Ground | |-------------------------------------------------------------------------| | | | | | | | | 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 | | | | | | | | |-------------------------------------------------------------------------| | +5V EN \VMA \VMA \VMA | | orginal sync out | | | | 74 F 157 | | | | | | SEL Ground | |-------------------------------------------------------------------------| | | | | | | | | 1 2 3 4 5 6 7 8 The SEL is now synconized with 7 MHz so that you simply can switch between 7 and 14 MHz without \HALT (this was in the last release) while the Amiga is running and it shouldn't crash. This is done with a D-flipflop 74F74 (also fast (F) type!) : 14 13 12 11 10 9 8 | | | | | | | |------------------------------------------------------------| | +5V | | | | 74 F 74 | | | | | | Switch | | +5V input 7 MHz +5V SEL Ground| |------------------------------------------------------------| | | | | | | | 1 2 3 4 5 6 7 (Switch input is +5V or Ground) (SEL is select output used by the 74F157 as input) The next thing I added is a jumper (J1). This will vary the way \DTACK is syncronized. The middle must be connected with the left OR the right side. (74LS27/2 is connected with 74LS74/9 or with \DTACK - some machines only work one way ... because it's an Amiga !) To smooth the flanks I added eight (C3-C10) capacitors (100nF). REBUILDING : ----------------------------------------------------------------------------- It's double sided. The lower side is the reflected image. I made a hardcopy and it looks well. For better results use a 2:1 scale if you can. There's only one through-connect (between the 74F157 and 74LS112). To make this possible I had to change the choice of the circuits of the 74LS86 and 74LS04. So watch out if you compare Livio's circuit plan with my layout. Also the IC's have different numbers ! Amiga 500 owner should not plug the MC 68000 in a socket (it's to high), but they will need a 64 pin socket as a distance to the ROM. The accelerator plugs by two 32 pin strips in the CPU-socket. Parts you need besides : - 2x 74 F 157 - 1x 74 F 74 - 1x 74 F 86 (replace for 74 LS 86) - 8x 100nF - 2x 22pF - 2x 560 Ohm - 1x 10KOhm - 1x 64 pin socket - 2x 32 pin strips - 1x single switch ----------------------------------------------------------------------------- Wanting to know the acceleration precise I wrote a CPU performance test program (See performance directory). Look at my tests and things come clear. Special thanks to Livio Plos for his great and cheap Amiga accelerator. Thanks Livio ! Any critiques, suggestions, questions, etc. are welcome ! Joerg Richter Dresdener Strasse 21 2150 Buxtehude GERMANY EMail: Joerg.Richter@arbi.informatik.uni-oldenburg.de --------------------------------------------------------------------------- How to get a PCB : If you want this PCB you may buy it from Joerg or Livio for DM 50,- or US 30$, this include shareware contribute.