Heatsink Replacement for a 6100?

[BeniD82]

Hi Guys,

I have been contemplating on moving the Cyrix 5x86 CPU which I am currently using in my 640 DOS Compatible onto the 6100/66's DOS Card. Since the Cyrix CPU requires an interposer which converts the 5V provided by the card's socket to 3.45V which the CPU requires, there would very little clearance left between the two CPUs (they are just about on top of each other). It seems that the 601's passive heat sink uses a significant amount of space, so I was wondering if you guys think using e.g. the heatsink from a 6500 in combination with a fan would suffice to cool the PPC 601? The 601's can get pretty toasty, at least when passively cooled, so my presumption is that with active cooling I might be able to pull it off. What do you guys think?

Since I am at work I can't provide actual screenshots so I shamelessly ninja'd two from Zone6400 and the Internet respectively

Current Heatsink:



Potential Replacement:



Other considerations are that the Cyrix does not require active cooling and has a "built-in" heatsink on the ceramic itself so it would use less space than the current DX2/66 and its taller passive heatsink.

Anyway ...

~BeniD82

 

[trag]

Ultimately the answer is going to be, "Try it and see if it works."

I can add that some of the 601 based machines did ship with a flat waffle iron type of heat sink similar to what you have in the picture there. The early Power 80, Power 100 and Power 120 machines from Power Computing used a flat heat sink rather than the cage type found in the 6100/7100/8100. Also, the heat sink on the PPC601/120 CPU daughter card in the early PowerCenter used the flat type. However the flat ones all covered a little more surface area than the square cage type heat sink.

With a fan, it will probably be okay.

Be sure to clean the old heat sink grease off of the CPU and apply new grease. Having fresh grease will go a long way towards improving your cooling.

 

[Macdrone]

6100 used to have a clip on accelerator and it came with a fan that slid snug right inside the heat sink.

 

[uniserver]

just be slightly careful when putting the HS back on,

here is a thread i did about the 6100 cpu easily breaking in half:

viewtopic.php?f=11&t=19313&p=184092&hilit=6100#p184092

if you just put a small fan inside (close to the top) of the HS,

get power from the Molex right there form the hd, wire it up to the 5v side,

It will take that HS down to just warm to the touch. Also the 12v cpu fan running at 5v is whisper quiet

 

[BeniD82]

Hi Guys,

Yeah, I was pretty weary at first taking off the stock cooler since I've read the article about cracking/breaking 601's. I removed the board from the case and made sure to be extra careful when unclipping and replacing the heatsink. So far so good and no damage done *phew* Trag, after taking off the stock heatsink it was pretty obvious that new thermal compound was needed. The stuff was so dried up it wasn't even funny - almost like plaster you use for spackling drywall ... yeah ...

I ended up using the heatsink that came with the 486 DX/2 that I pulled off the DOS Card since it offers quite a bit more surface area in comparison to e.g. the heatsink from a 6500 (see the "potential replacement" screenshot, it's tiny and seems to me that it might not be large enough). With the Cyrix 5x86 and it's attached heatsink, interposer and all, and the 601 with the 486's old heatsink, I have about 12-13mm clearance left between both CPUs. I wasn't able to use the stock heatsink since it's just too tall (I have considered just dropping in a fan but the height of the fins won't allow installation of the card).

I haven't been able to get too much testing done since I had to get some sleep before work, but I ran the setup without fan for a little while (half an hour or so), using both the Mac and PC side of things to see how hot it actually gets (with case closed and machine slightly raised to allow proper circulation). The Cyrix seems to be just fine, the 601 does get quite warm even with the heatsink.

Since there really isn't that much clearance between the CPUs I've tried to figure out a way to see if I could possibly add a fan sideways rather than on the heatsink in order to force airflow over the fins (like some of e.g. the Sonnet G3/G4 accelerators do). Doesn't seem to be an easy way to accomplish this.

I was able to mount a 40 x 40 x 10 fan on top of the 601 which *barely* fits. Since the CPUs are not directly stacked on top of each other, but rather slightly offset, there is some room for the fan to draw in air and to force air over the heatsink, but I have not been able to test how *hot* it actually gets yet with that setup. I ran it briefly without the DOS card and it indeed only got lukewarm (which is good) but it remains to be seen how it will perform "in the field", with DOS Card installed and case closed.

I've seen some of these heatsinks which came with e.g. the 601 addon cards, they seem to be not quite as tall as the 6100 contraption, but seem to offer quite a bit more surface space. Not sure if this will work in a 6100 considering e.g. capacitors, chips, etc which might obstruct the heatsink, but I might look into that. It would definitely not use nearly as much vertical space as the other sinks I've tried so far...

In the end, you may ask why bother with all this if there are different machines which can do exactly the same, if not faster and better? Well...

1.) The 6100 was the first PowerPC machine (sentimental value)

2.) I like the pizza-box form-factor

3.) A "VM" implemented in hardware (an x86 compatible CPU grafted to PPC architecture) is total geekery which I like

4.) I have both old Mac and DOS/Win3x titles which I can bring "under one roof" with this setup

5.) Regarding the Cyrix 5x86, it "smokes" the Intel 486 DX2/66 - when comparing 486s that is

Getting off the soap box now, so If you've made it this far, thank you for listening to my ramblings (3:20am and my brain's not working)!

~BeniD82