Amiga upgrades



14MHz power to A500...

For crazy people only


This is compilation of other people work. I build it by myself and it works. You can download original document from Aminet. I reccomend to build more complicated version, because it allows you to switch CPU speed while working and allows you to add my hack which dissables problems while reading from flopy disk. Also I reccomend you to use oscilator pin instead of Agnus chip pin #34. First of all it is shorter way and you didn't need to touch that big socket. Also you don't need to touch denise chip and it pin #35. Connect this line to CPU socket pin #15. Then you install this hack the only change to A500 PCB will be aditional wire to R near oscilator and wire to power connector. Bend CPU pin #15 before installing it to the socket, one wire will go to socket another to CPU pin.
So always you will be able to cut all aditional wires and put original CPU to restore original a500!
You need: Connect chips according this picture:


Note the delay line build from 74LS00. In my case I need to build it from 4 elements. That's ALL! But I had problems with my flopy drive. It was too slow to move the head in time. There is software patch in original posting, but it is very complicated to place the patch in game's custom boot block. But there is small hack to hack :). It removes the need to use the patch. Locate line going from keyboards MOTOR light to mainboard. Connect this line using diode and (I don't remember if you need to invert signal) few 74F00 elements to switch, R, C and 74f74 D input. If you didn't place the diode the switch will turn disk drive's motor on too :)
Now, when the computer wants to read from flopy it switch motor on, in same time reduces CPU speed to normal 7MHz. When motor is off, the CPU speed is high. In some, very old and badly programmed games you need to reduce speed to 7MHz, so use the switch.

ORIGINAL POSTING:

Short:    Brute force A500 14MHz hack
Uploader: layling@intercoast.com.au (Leslie Ayling)
Author:   layling@intercoast.com.au (Leslie Ayling)
Type:     hard/hack
Replaces: hard/hack/14Mhz.lha

This is a collection of all the doco and pics relating to my 14MHz processor 
accellerator for the A500. It also contains extra notes and pics by:
Ray Taylor and Ian Mills.

This file replaces hard/hack/14MHz.lha which has been uploaded without my consent.
The files originally appeared in the Australian on-disk magazine "MEGADISK"
around 1989-1990, hence the references to local Sydney based companies.
The information is somewhat passe' however it may be useful for people trying to
understand the hardware a little better.

#addendum to the ACCELERATOR project      Leslie Ayling

Some people have complained of problems using the mod with the serial port.
This could occur as the frequency of the clock on the two CIA's is now
double as they are both fed from the E clock of the 68000. Hence if our
68000 clock is doubled the E clock is also doubled. Therefore the timers in
the CIA's will be operating at twice the speed as normal .

When selecting the BAUD rate on any particular program just divide by two.
In other words if you want to use a 2400 baud modem through the serial port
just select 1200baud on your communications program.
or if you are using 1200 baud modems select 600baud from your menu.


IMPORTANT NOTE: you always can break something in your Amiga. So please be carefull

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