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6100/66 Modding/Cooling

dr.zeissler

Well-known member
Hi there,

I want to optimize my 6100 machines these are the targets:

1. Replacing the caps on the board
2. Adding heatsinks on the big chips
3. Checking the fan on the power supply
4. Adding an additional fan to the case
5. Adding a bigger L2 Cache


Hopefully someone can give ma some tips on this toppics.

Greetings
Doc
 
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dr.zeissler

Well-known member
Target1 => This is done by BOLLE so this could be marked as done ;)
Target2 => I already bought some 28x28x6 and some 28x28x8 heatsinks in china and I will perhaps receive them in some weeks.
Target3 => I will check if some finemecanical-oil will do the job.
Target4 => Some mentioned that he put a PCI-Fan in the machine. That would be interesting.
Target5 => Very very hard to find the 1MB L2-cache (apple offered only 256K L2), but perhaps there are ways to get around this.
 
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dr.zeissler

Well-known member
Yes I have two of them but I have not figured out how to get the plastik out of the machine and I believe it would be put top2bottom and it sucks air in the machine and blows it right to the both cpu's (PP66/486/66) or am I wrong here? It should be placed under the harddrivebay which is in my case a blueSCSI so no power required and generating no heat.

Perhaps someone already did that PCI-Slot cooler mod and can tell me if I am thinking this right.

I am not sure about the fan in the power supply I beleive it sucks air in and blows it over the mainboard and it get's out of the machine where the additional PCI slot blower is mounted...but then both fans suck air in the machine, I thought thy should work the same way round, but with that PCI-Slot cooler this will not work. The only way is as I described above.

Thx!
 

Phipli

Well-known member
Yes I have two of them but I have not figured out how to get the plastik out of the machine and I believe it would be put top3bottom and it sucks air in the machine and blows it right to the both cpu's (PP66/486/66) or am I wrong here?

Thx!
I suspect you would need to put it in upside down, yes, but can't be certain, it depends on the design. Its most likely an extract fan.

Correctly aimed it would blow air near the CPU, but I advise checking on airflows. If that vent under the disk is an outlet, I would add a thin fan blowing /outwards/.

If you push air in at the psu and in at the outlet, the airflow will stall somewhere in the case and you might make cooling worse.

This video shows how to get the plastic out. Thanks Jason :)

 

dr.zeissler

Well-known member
Yes extract fan but if you look how thy are designed this will not work. Only way seems that it does not blow out and therefore blows out to the CPU's.
 

dr.zeissler

Well-known member
In my opinion the only way to put such a thing into the PM6100, but I have to cut those in order to make the fan fit and not bend the hdd-bay to the top.
 

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ymk

Well-known member
The slot cooler is likely pointless.

The negative pressure generated by the PSU fan already pulls air through those slots.

On the PSU fan, just replace it with something modern. It's not a serviceable part.

Absent from your list is the hottest part of the system - the CPU.

There's lots of room for improvement over the stock heatsink, but mounting is tricky.
 
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dr.zeissler

Well-known member
Interestingly the caches are not identical :)

One machine on the shelf had a different, not apple-branded L2cache. If it has more than 256KB I don't know, because the machines are currently disassembled. Hopefully this cache is 512KB or even more...

argh, sorry for putting the first L2 in the wrong direction compared to the other two...
 

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dr.zeissler

Well-known member
On what chips of the board should I place extra heatsinks. The fout bigger ones near the CPU of course. What about the SCSI-Chip, or the RAM-Dac (which is much smaller). What do you think?
 

Phipli

Well-known member
On what chips of the board should I place extra heatsinks. The fout bigger ones near the CPU of course. What about the SCSI-Chip, or the RAM-Dac (which is much smaller). What do you think?
I'm not sure that you need to put them on any?
 

dr.zeissler

Well-known member
The 6100 has an overheating issue. Big problem is with the 486/66 card where both CPU's heat each other and the metal-housing of the houdini-card get's so hot, you can't touch it for a longer time. Ok I use blueSCSI so the heat from the HDD is gone, but for the long run I think passive heatsinks are not a bad idea.
 

Phipli

Well-known member
The 6100 has an overheating issue. Big problem is with the 486/66 card where both CPU's heat each other and the metal-housing of the houdini-card get's so hot, you can't touch it for a longer time. Ok I use blueSCSI so the heat from the HDD is gone, but for the long run I think passive heatsinks are not a bad idea.
Yes, I agree the CPUs get warm, ventilation isn't great and the 486 heatsink sits inside the 601 heatsink, but I'm not sure (unless something is known for overheating) that there is much need to add heatsinks to other chips.

My feeling is that the machine was designed for it - I'd consider re-pasting the heatsinks if its overheating and crashing (remember old computers crash sometimes anyway, so we're talking about crashing when you load it up on a hot day). Given it is quite a tight case, if that isn't enough I'd consider making something like one of those laptop stands with fans.

The reason I say that is because small fans are noisy and you'd need a small fan to fit in the case easily. Take care if you decide to replace a fan. The PSU fan will be designed for a higher backpressure than many modern PC case fans - modern cases generally have large open areas and most fans are designed to shift a significant air volume against a small backpressure. A 6100 is a bit of a long and winding path compared to a modern case.

I would smile if you added a water cooling system though :)
 

Phipli

Well-known member
Also, a second fan in the same air path as an existing fan does make a difference, in a HVAC system each section of the "duct" is a resistance, and the fan is like a battery supplying voltage to drive a current. Two fans in series in the system result in an increased airflow (like the increased current from two batteries doubling the voltage) as long as they're not really poorly sized (and acting as an obstruction). Booster fans are a thing in longer duct systems.
 

ymk

Well-known member
Cooling the 486 is a better bet than the SCSI or ethernet chips.

If there's little clearance, vapor chambers are good at moving heat sideways:


Thick foam weatherstripping can be used around the PSU fan, under the case, to direct the air to the rear.

Otherwise, the exhaust heat can be reabsorbed through the case floor.

Cutting out the PSU fan grille will improve airflow and reduce noise.

Another option is building a passive intake duct to guide air from the floor vents to the CPUs. I'm cooling a Pentium 83 Overdrive in a single fan system using this method. The drawback is, it doesn't work with the cover removed.
 
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