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). 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.