Fastest 040 CPU?

[Neo]

Hi fellow Amigans,

What is the fastest anyone ever clocked a 040 cpu?

These are my current tests with two different 040's

XC68040RC25A
25MHz (No heatsink) - Can be used to boil eggs
33MHz (Heatsink and fan) - Body temp (very stable)
40MHz (Heatsink and fan) - Crashes if datacache turned on

XC68040HRC25M
40MHz (Heatsink) - Lika a hot day in Sahara (no problems so far)

My guess is that the latter one could be clocked up even a little
further. Especially when I put the fan back on.

So, is there anyone with a 50, 60 or even 66MHz 040 Amiga?
I'm eager to hear! (060's are just to expensive)

[x56h34]

My 040 clocked @ 25Mhz is very cool. I don't even use a heatsink on it. Why is everyone so upset about its heat and all? It's fine... although I wonder if it would get hotter if I were to ever use it in an accelerator card or anything, away from my big box of chips.  :-P

[amipal]

I have a 25Mhz on my BlizzardPPC, and it used to make the side of my PowerTower warm to the touch. Once I found that out I bunged a 486 heatsink and fan on their pretty sharpish.

[Neo]

It appears that there is a large difference in heat generated from
different 040's.

The first one in my listing was from a GVP board.
Originally I used it together with the original Quantum harddrive
which together generated so much heat that you seriosly got 1st degree
burns if you put your hand behind PSU fan. I used to call it the
plasma went.

Measuring the temp of the other CPU i test at 40MHz is actually only
at 45°C, so it's just like a warm day in Tikrit I think.

Be happy you got one of the good ones!

My CyberstormPPC board actually made my machine to run cooler. But the
worst heat sources are old crappy harddisks. Beware of those!

[Karlos]

Anybody tried matching the crystals for the 040/060 and PPC chips on a blizzppc?

From some discussions with Patrik, it seems possible that faster memory access on the 680x0 side is possible if the bus speed of both CPU's is the same.

Hmm, where can I get a nice  60MHz crystal?

[Neo]

@Karlos

Did it on my CyberstormPPC! Upped the System/040 osc. from 50MHz to
60MHz and I can tell FroggerNG played back movies a helluwa faster.
(approx. 5 times faster)

Also, tried using a single 66MHz osc. to feed both CPU's but the boost
was just like 2 times or so over using twin 60MHz osc. (Still worth
it)

From what I found out it seems the most important part is the clock
the 68k CPU as fast as you can manage, since the 68k is the one that
feeds the PPC and so the PPC never gets faster than the 68k can feed
it with work.

[adolescent]

@x56h34
Heh, yes chips that aren't in computers tend to stay much cooler.

Anyway, my MC68040RC40 doesn't generate much heat.  Although, it's clocked down to 35MHz in my Mercury and has it's built in fan.  Someday I'll get around to getting a crystal and upping it to 40MHz.

I think the fastest would be the Sonnet QuadDoubler, which is a 50MHz clock, with peltier cooling.

[patrik]

@Karlos:

Here you can get a crystal:
http://www.elfa.se/elfa/produkter/en/2019471.htm




/Patrik

[Neo]

Well, thanks for the answers.

I did some research and it appers that people that do some serious
overclocking don't do more than 40MHz for the RC25 models. I haven't
seen anything about overcklocking RC40 models. But that might be that
not many people thinks the RC40 is worth the price.

Tried 50MHz but it appeared my 100MHz oscillator was broken because it
got very hot and nothing else.

I'm thinking of trying to find out what the maximum speed is but
oscillators are expensive so I want to limit the range of frequencies
to test with. That was the reason for my questioning.

[Jose]

I have a 040 at 40mhz. Without cooler it's too damn hot!! You could fry eggs on it. With cooler it actually just warm! I think with an appropriate crystal and socket it would easily go faster. I've read here on forums in the past some people having their's to 45mhz if I remember correctly.
I would'd mind getting a crystal and a socket but it's damn expensive for what it is...

[Jose]

By the way, is 64mhz better than 66mhz cause it's a multiple of the bus speed or something??? :-?

[danamania]

On a mild (ok completely reversed detour from the topic, what's the slowest a 68040 can go? I've heard from a tech who works on PPCs that there are very definite lower limits to PPC7400 operating speeds, but is the 68040 the same?

If I REALLY wanted to, could I have an 8MHz 68040? or a 2MHz one? And would this be completely daft and pointless?   :-D

dana

[patrik]

@Neo:

I saw that you mentioned using just one crystal to feed several clocklines, does this work without any problem?

@danamania:

If I recall correctly, the low voltage 68040 version supports from 0 to MAX MHz officially. Dont know about the standard 68040, though 8MHz should be ok. This would be useful when constructing something experimental on a lab-board or something similar as such an environment introduce a lot of crosstalk, signal disturbance, etc making it hard to run at high clock speeds.


/Patrik

[Neo]

@Patrik

Yes! I put a 66.667MHz osc. in the center slot (System/68K) of my PPC
board and made a wire to the PPC oscillator slot.

No strange crashes! But on the other hand haven't got them since I
started overclocking. My Amiga likes going fast!!! :-)

[Neo]

@Jose

Might depend on what board you have. For the CyberstormPPC board it
appears that the only thing that matters is to use as high rates as
possible. Could be different for 060's though. (They use different
clocking)