4000/040 running at 35 MHz (!).
		       (by Luigi Pasciuto)

      (Update for 4000_33M.lha available on Aminet hard/misc)

********************************************************************
This is a 'beta' version of the doc. Please send me    any questions
you have to complete it so that everyone can use it.
********************************************************************
 
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IMPORTANT: this is a modification on A3640. HW manipulation skill is 
           required so MAKE CARE ! TAKE CARE to electric static dis-
	   charge, you have to be grounded before proceed !!!
********************************************************************

This is a tip for everyone want to  accellerate his  A4000/040 spen-
ding not much money.

Cause of my raytracing jobs, i need more MIPS by CPU. The less expen-
sive accellerator for A4000 cost $ 600 at least (with nocpu on board).
For example: Warp Engine  28 MHz costs $ 700 with no CPU, using this
tip you will spend $ 50 and will obtain same performances like  Warp 
Engine, the difference 700 - 50 = $650 are in your pocket!
Is it suited for you ???

So I've tried to modify my A3640 CPU board to improve performances.
The way is to replace the existing original oscillator  on  CPU board
(50 MHz) with another at higher value (68.7 MHz). I can't assure that
this tip works fine on every A3640  board. It depends on  68040 clock
tolerance. Normally, 68040 25 MHz are used in 28/30 MHz accelerators,
the probabilities that it works with 35 MHz are good.

If your board doesn't  work with 68.7 MHz, try a 66.7 MHz (see my old
doc "4000_33M.lha on Aminet hard/misc", I can assure you that in this
case it will work fine.

The substituition of the oscillator on the CPU board don't cause any
damage if you respect my advices.

First of all, turn  off your A4000, open the case and remove the CPU
board A3640. Using a well grounded solder, remove the original oscil-
lator and keep it. Take  note of oscillator orientation on CPU board
before remove it. Now, solder a 14 DIL socket on oscillator place on
the board, then insert  the new oscillator  (68.7 MHz) in the socket
respecting the right orientation (have you noted it before ?).
Stick a CPU cooling fan  on the 68040  heat sink so that it push the
air jet on  the CPU. Connect the  cooling fan  to 12 V  power supply 
available on  spare hard disk  connector. Now "cross the finger" and
power on the A4000, is it booting up ??? Yes ??? WHOWWWWWW !!!!!!!!
That's all !! Now you have a real 27 MIPS A4000 !!!!

I'm using this tip since 1994 and it works fine without any trouble.
Everyday I use my A4000 for 5/6 hours continuos with no trouble.

The use of higher clock cause an increase of power consuption of CPU
so it must dissipate more heat. Using the CPU cooling fan, as descri-
bed before, you prevent CPU damage. However it's possible, specially
in hot region and hot season, that CPU cooling is not enough. In this
case you'll note a decrease in speed of system performance, the Ami-
ga will slow down to stop. Dont' worry, this is  a protection system
developed by Motorola to prevent CPU damage. In this  case power off
the A4000 and wait for CPU cooling, the system will restart again.

On my A3640 board I've tried a 66 MHz oscillator but it fail.

I didn't test this tip on other configurations, but  i think that it
must work fine the same.

The AIBB 6.5 program report an  average increase  of performances of
35 % with a maximum of 41 %. Unfortunately  this tip  cause a  raise
of  CPU/memory  latency  index: from 8.1 to  9.1, but you can  patch
this using copymemquick program, available on Aminet.

68040 at  35 MHz  permits  an improvement in hard disk transfer rate
too, in this case you i must verify, using  DiskSpeed 4.2, if  there
are errors with the higher speed, in this case you  must  modify the
MAXTRANSFER  parameter in  HDToolBox  program  to 0000ffff. My  hard
disk (Western Digital  340 Mb, slave) transfer  rate  is raised from
1.3 Mb/s to 1.6 Mb/s using the MAXTRANSFER value mentioned above.
 
In the pictures joined to this doc you can find an aid to modify your
A3640 board and benchmarks obtained with AIBB 6.5.

This is FREEWARE, I accept everythink as reward for it (thanks too !)
If you have any trouble, contact me at the following addresses:

	Internet: pasciuto@settimo.italtel.it

	Home:     PASCIUTO LUIGI
		  VIA VERGA 10
		  20015  PARABIAGO (MI)
		  ITALY

Good MIPS at all !

P.S. I have all the parts necessary to tip your A4000, CPU replace-
     ment, Motorola documetation for developing HW/SW. Do you need
     oscillator, fan, socket ...... ??? Call me !!!!

                          HELP, HELP, HELP !!!!
     I'm looking for SuperBuster rev.11, I want to exchange it with
     a 68LC040 good as 68040 original replacement.


-Luigi.