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Old 26 July 2013, 20:24   #1
droopy
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A4000 040 overclock kit ?

I recently buyed an a400 040, works great and all is recaped..
When I got it I also got an 68040 rc cpu at 40 mhz and a 70mh crystal "outside the package"

ofcource I am curious to add this extra stuff.

Is there any concerns ? Am I risking the computer in any way ?

I do have some soldering and basic electronics understanding (Im an electrician by profession) (240V+)

Any advice ?

Last edited by droopy; 27 July 2013 at 08:32.
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Old 26 July 2013, 22:56   #2
TjLaZer
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You cannot overclock the A3640 past 33Mhz without some serious lockups. With 33Mhz you may have to do the delay line mod, 30Mhz will work pretty good. The only issues with OC are heat, you will have to do some serious cooling in that desktop.
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Old 27 July 2013, 08:39   #3
droopy
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33Mhz sound ok Ithought having a 40Mhz cpu would cool it down running at 33Mhz.
I also have 60 ns ram sticks in the 16Mb slots..

I read somewhere that some other components need a change (some GAL chip's)
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Old 27 July 2013, 08:51   #4
alexh
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You should talk to SpeedGeek

He did several A3640 upgrades including changing several of the GAL chips on the board and adding an extra frequency synthesizer. The result was much more stable, lower RAM access latency and it could run at 50MHz fine.

http://www.amibay.com/showthread.php?t=19993
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Old 28 July 2013, 22:14   #5
hooverphonique
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Mine runs at 33MHz (66MHz osc) without any extra mods and it runs fine, but your mileage may vary - the delay line next to the osc generates a 90 degree out of phase clock (10 ns delay), but this doesn't alway work with 33MHz - using the 5 ns delay tap sometimes works better, but depends on your 3640 and mobo (@33, the delay should ideally be 0.25 * 1/33 = 7.6ns)..

note that when overclocking the 3640 by "just" exchanging the osc, you overclock most of the motherboard as well - that's why you need 60ns ram @ 33MHz. Speedgeeks 50MHz machine is modified in such a way that the motherboard runs (async to the 3640?) at 25MHz, that's how he's able to go to 50MHz on the 040.

Last edited by hooverphonique; 28 July 2013 at 23:13.
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Old 29 July 2013, 17:21   #6
alenppc
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I am planning to do SpeedGeek's mod. Can anyone suggest a GAL programmer which can program PLD22V10-10 & PLD16V8-7 type of chips?

Can the Commodore chips be erased and reprogrammed or do I need to find new ones?

Thanks.
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Old 29 July 2013, 20:42   #7
hooverphonique
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Quote:
Originally Posted by alenppc View Post
Can the Commodore chips be erased and reprogrammed or do I need to find new ones?
As far as I know, there's no definite answer to this, so you'll just have to try, or maybe better keep the original chips as backup?

the willem and wellon programmers seem to be very widespread with the latter being the better brand - they are both still cheap chinese items, however..
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Old 27 August 2013, 11:36   #8
droopy
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I have the 68040RC40 cpu So the CPU should run quite cool at 33Mhz.
What chip's need extra attention regarding heat ?
My fastram is 50ns 16M So I think they would run cool to at 33 Mhz

So if I replace the crystal to a 66Mhz one.. are there other chip's that might need cooling or to keep an eye to.

One thought woul be to measure the temperatur Before/and after the mod (have IR temp gun).
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