Q:Commodore A3640 tinkering - Watch out I have boing balls!

arnljot

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Question.

Can I replace the 25mhz 040 with a 40mhz one and a 80mhz crystal?
 

rkauer

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Re: Q:Commodore A3640 tinkering - Whatch out I have boing balls!

Re: Q:Commodore A3640 tinkering - Whatch out I have boing balls!

Yes, but you need to modify the board a little.

A3640_Delay%20line%2066.666MHZ_r350.jpg
 

arnljot

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Re: Q:Commodore A3640 tinkering - Watch out I have boing balls!

If I supply the parts:
-25mhzA3640
-80mhz crystal
-40mhz 040
-stump of wire

Can Some one fix this for me then? Pretty please?
 

rkauer

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Re: Q:Commodore A3640 tinkering - Watch out I have boing balls!

Just remember: if your board is the crappy 3.0 version, forget about it!

The only upgrade you can do on the 3.0 board is replace the EC/LC CPU for a full 040.

BTW: you cannot overclock a 25MHz unit to 40MHz! You'll end with a very broken CPU. 25MHz can be overclocked to 28MHz, tops. 33MHz units can go to 36~38MHz and 40MHz units can go up to 44~48MHz.
 

arnljot

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Re: Q:Commodore A3640 tinkering - Watch out I have boing balls!

I have no idea what version it is. It has no sticker on U209.

It just reads:
TI
22V10-10CFN
40307XWAF

Is there any software way to tell?
 

arnljot

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Re: Q:Commodore A3640 tinkering - Watch out I have boing balls!

Comparing pictures at amiga.resource.cx and bboah.com, it seems that I have a V3.1, heatsink and other stickers match up with the 3.1 version, the 3.0 and 3.2 version stickers differs. If it's anything to go by...
 

rkauer

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Re: Q:Commodore A3640 tinkering - Watch out I have boing balls!

BTW, here is another useful link with a bit more information (and a crappiest photo). :wink:

If you find a MC68040 (not the fry-an-egg XC68040), you can overclock even the 25MHz over 40MHz without issues (on 3.1 and 3.2 boards).

Your board don't have any sticker? All chips have the -01 sticker (but the CPU), only U204 have the -02/-03 sticker. Also there is the version printed on the board, near the socket.
 

arnljot

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Re: Q:Commodore A3640 tinkering - Watch out I have boing balls!

rkauer said:
BTW: you cannot overclock a 25MHz unit to 40MHz! You'll end with a very broken CPU. 25MHz can be overclocked to 28MHz, tops. 33MHz units can go to 36~38MHz and 40MHz units can go up to 44~48MHz.

I was planning to buy a 40mhz 040 (XC68040RC40M). And then put a 80mhz crystal on the board in place of the 50mhz crystal that's there.

But the only text I've found so far which suggests that it can be done is here: "Overclocking the Commodore A3640"

Overclocking the Commodore A3640 said:
I have overclocked three of these boards, by replacing the 50MHz oscillator by one rated at 60MHz. This gives 30MHz for the 68040. All systems work reliably at this speed, and it's an ideal way to get some extra performance out of this board. I have heard of other people getting more. One user has been able to clock this board as high as 40MHz, and another I have heard of, has managed to get 37MHz. These two users were not able to get a lower speed of 33MHz, possibly because of the design of the A3640, which uses delay lines for part of it's clock circuitry. These delay lines provide a fixed amount of delay which becomes inappropriate when the clock frequency is changed too much. I suspect a "wrap around" effect occurs when the frequency is increased still further, the amount of delay once again becoming more or less correct over 37MHz or so. Recently I have become aware that it is possible to change the amount of delay from this delay line, so that it is now possible to overclock to frequencies such as 33MHz, and possibly more.

So, I realise it's pretty thin... So, does any one know - can it be done?

Edit: You beat me to it with the link... :-D
 

arnljot

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Re: Q:Commodore A3640 tinkering - Watch out I have boing balls!

rkauer said:
If you find a MC68040 (not the fry-an-egg XC68040), you can overclock even the 25MHz over 40MHz without issues (on 3.1 and 3.2 boards).

Ah, crap. I've only found an XC - I'll continue to scout for an MC then.

rkauer said:
Your board don't have any sticker?
U401, U208, U207, U213, U203 and U400 have stickers. They all say "*-01" and stuff like "exlat", "term" "mapper", "rst", "lebus" and "oebus".

rkauer said:
Also there is the version printed on the board, near the socket.

Aha! I do have a 3.1 board :)
 

rkauer

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Re: Q:Commodore A3640 tinkering - Watch out I have boing balls!

A german guy on the other bay was selling those lovely chips a little time back...

Worth a look, don't you think? :wink:
 

Zetr0

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Re: Q:Commodore A3640 tinkering - Watch out I have boing balls!

@arnljot

get yourself an MC68040 full core @ 40mhz m8, much cooler!!! (XC's are toasty chippies)

once you have all your kit PM me, I am sure I can help. I have a 33mhz 040 version of the A3640 that I will do this mod too as well me thinks :D
 

TheCorfiot

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Re: Q:Commodore A3640 tinkering - Watch out I have boing balls!

Zetr0 said:
@arnljot

get yourself an MC68040 full core @ 40mhz m8, much cooler!!! (XC's are toasty chippies)

once you have all your kit PM me, I am sure I can help. I have a 33mhz 040 version of the A3640 that I will do this mod too as well me thinks :D


TC's ears perk up :LOL:
 

arnljot

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Re: Q:Commodore A3640 tinkering - Watch out I have boing balls!

Thanks Zetr0.

I'll come back to you when I have all my ducks in a row.
 

rkauer

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Re: Q:Commodore A3640 tinkering - Watch out I have boing balls!

This time I only found a pair of used equipment with those chips inside, don't know if socketed... :|
 

arnljot

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Re: Q:Commodore A3640 tinkering - Watch out I have boing balls!

Yeah, I googled and "040 68040 +otherbay", and checked .hk, .ca, .com, .de, .ca, .co.uk, .sg and .my Nada. Just those embeded ones. And two were sufrace mount types. And one PGA at 33mhz. Going from 33 to 40, isn't maybe much. But I'd rather be "purist" on a hack like this.
 

rkauer

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Re: Q:Commodore A3640 tinkering - Watch out I have boing balls!

If you find a MC type unit run for it.

Doesn't matter if the mask says 33MHz!

It will be good to use at 40MHz and even more! :D
 

Kin Hell

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Re: Q:Commodore A3640 tinkering - Watch out I have boing balls!

From my experiences.........

Not sure the A3640 is actually capable of a 40Mhz CPU anyway, even if you fit a 40Mhz CPU part....

The reason being, the mod shown here by rkauer is NOT needed for swapping a Crystal & O/C-ing the CPU. How fast you can go depends on the "Quality" of your CPU,

My Rev 3.1 040 clocked to 33Mhz without wires traced all over the place.....

I guess plugging in a 40Mhz CPU & a 80Mhz X-Tal is the only thing to do for being sure!

XC or MC doesn't matter imo. The 040 even @ 25Mhz is better suited with a Fan/Heatsink combo in an A4KD anytime. In an A4KT, you might get away with Passive 40Mhz CPU, but this depends on Air flow through the case & I suspect a bog standard A4KT is not going to cut the cloth. :wink:

Kin
 

arnljot

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Re: Q:Commodore A3640 tinkering - Watch out I have boing balls!

Kin Hell said:
I guess plugging in a 40Mhz CPU & a 80Mhz X-Tal is the only thing to do for being sure!

This is the way I plan to go. And now, by your reccomendation seeing as this is planned to go into a desktop model, also with a fan and heatsink too now.
 

Kin Hell

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Re: Q:Commodore A3640 tinkering - Watch out I have boing balls!

So you don't fancy my XC68040 40Mhz I have here then?

Kin
 

arnljot

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Re: Q:Commodore A3640 tinkering - Watch out I have boing balls!

Oh yes!

:)

I'll place a wanted asap.
 
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