I stumbled across this A500 speedup hack on Aminet (
http://uk.aminet.net/docs/hard/500hacks.txt). A 150% to 200% increase in speed simply by getting a faster rated 68000 and doing a few simple mods? Can it possibly be that simple and easy? I don't think so as I've never met anyone who has actually done it. You'd think that if it was this easy nobody would bother with 68010s or Mega Midget Racers.
viii. Double Trouble
--------------------
The hack to accelerate your Amiga to 14MHz has been published in countless
articles, but I may as well include a brief description of it here. The hack
involves removing the original 68000 from your Amiga and substituting a
version rated at 16MHz (confusingly called the 68000P-12; the Motorola chips
have "16MHz" stamped on them, but the SGS-Thompson clones do not). The clock
pin is bent out and soldered to the output of a divide-by-2 counter whose
input is connected to the base 28MHz clock. THIS MODIFICATION SHOULD BE
INSTALLED WITH A SWITCH !! If not, you WILL (not may) find that some games
will refuse to load because they use timing-dependent loaders.
Aside from the problem mentioned above, the only compatibility
down-side to this modification is that some floppy drives will not handle the
increased step rate. If you find that your drives give read/write errors at
the high speed, you can either replace them or run a program called "DFDelay"
to slow down the step rate. (If df0: will not work, you have a problem. Try
swapping df1: for df0: - to do which you will need a Commodore df1:. The
mechanisms used in the old A1010 drives are EXTREMELY reliable and much
quieter than the new rubbishy things; if you have an A1010, you can be fairly
certain that it will support the new speed).
To perform the mod, remove your old 68000 and embed it in a perspex
block for future reference. Now rig half of a 74S74 dual D bistable as a
divide-by-2 counter. Connect the input of this to a convenient take-off point
of the 28MHz clock line on the motherboard (I use pin #34 of Agnus, but
anywhere will do). Now bend out pin 15 of the new CPU and solder a wire to
this pin. Take a piece of stiff telephone wire, strip approx. 5mm of
insulation from one end, and stick this end down pin 15 of the 68000 socket.
Insert the new CPU in the socket and verify that pin 15 is well clear of the
wire in the socket. Now wire a SPDT switch as follows :
BACK VIEW
+---+ When held as shown UP=7.14MHz,
To output of divide-by-2 counter -+-o | DOWN=14.28MHz
To pin 15 of 68000 -+-o |
To wire in pin 15 of 68000 socket -+-o |
+---+
The 74S74 should be mounted somewhere convenient; I break off all the unused
pins, bend the remaining pins out, and stick the chip on top of one of the
data path IC's; this has the advantage of allowing me to take power directly
off the existing components rather than stringing yet another pair of wires
through the machine.
If you only have chip and/or slow memory (see subsubsection iv-2.)
then your machine will run at approximately 150% normal speed (on
CPU-intensive operations; DMA rates will be unchanged). If you have true
fast-RAM then code running from fast-RAM will execute at close to 200% of
normal speed. Try placing a large perpective brush with anti-aliasing HIGH
in DeluxePaint III (or IV !) and you will see the speed increase.
