Heatsink for 68040/33 - heat dissipation efficiency?

[egrath]

Hi,
i'm currently restoring a Quadra 650 back to it's fully glory and thinking about which heatsink to use for the 68040/33. I have two options:

Option 1: Original Apple 68040 Heatsink:

The stock one already on it.

Option 2: Using one of these:


(Aluminium, 50x50x11 mm, would glue it on top of the cpu with 3M thermal adhesive tape)

As far as i know, the Centris 650 used something similar to the later one in the stock configuration. Which one would you guys prefer? I want to keep the 68040 as cool as possible without adding any further cooling solution like a fan on top.

Regards,
Egon

 

[Phipli]

Hi,
i'm currently restoring a Quadra 650 back to it's fully glory and thinking about which heatsink to use for the 68040/33. I have two options:

Option 1: Original Apple 68040 Heatsink:
View attachment 49869
The stock one already on it.

Option 2: Using one of these:

View attachment 49870
(Aluminium, 50x50x11 mm, would glue it on top of the cpu with 3M thermal adhesive tape)

As far as i know, the Centris 650 used something similar to the later one in the stock configuration. Which one would you guys prefer? I want to keep the 68040 as cool as possible without adding any further cooling solution like a fan on top.

Regards,
Egon

Either will be fine - testing would be needed to confirm which is better - one has more access to cooler air, the other has higher surface area. If you were using a fan as well, there would be no contest and I'd say the modern one.

Rather than thermal tape, have you considered silicone thermal glue? Its what I use with similar heatsinks.

 

[egrath]

Rather than thermal tape, have you considered silicone thermal glue? Its what I use with similar heatsinks.

No, never tried, always used either thermal conductive tape or regular thermal paste with physical mounting brackets. Can you recommend a specific one?

 

[jessenator]

FWIW the 040 doesn't generate enough heat to be worrisome (in my view) or even fail under normal operating conditions*.

(no heatsink, operational and running benchmarks)

The OE heatsink (bar style) you have shown should be just fine. But for maximum cooling, more surface area in the fin stack will be your best bet. Oddly enough, my Centris 650 came with the higher surface area heatsink, while my Quadra 650 board had the bar heatsink. Go figure.

Honestly, I personally wouldn't spend money on special thermal paste, and just use what was on-hand or what is cheapest.

*The caveat is if you're trying to OC an OLD 040 mask rev, like a D50D out of a 9x0 or 700. Those weren't great thermal performers:

 

[egrath]

Thanks for the reply, think i will stick with the one that came originally as i don't intend to do any overclocking at all

 

[bakkus]

JDW did some looking into thermal adhesives and copper heatsinks:

 

[Phipli]

No, never tried, always used either thermal conductive tape or regular thermal paste with physical mounting brackets. Can you recommend a specific one?

Something like this?

Halnziye HY910 10g tube Silicone Heatsink Plaster / Thermal Adhesive Glue | eBay

Halnziye HY910 10g tube Silicone Heatsink Plaster / Thermal Adhesive Glue | Computers/Tablets & Networking, Computer Components & Parts, Fans, Heatsinks & Cooling | eBay!

www.ebay.at

I clean the processor and heatsink with IPA, then put a few blobs (in a dice "5" pattern) on the processor, then put the heatsink on top and push it in circles to spread it out thin and to cover all of the top. Then wipe off any overflow. It stays soft for a few days so keep it level. After it has set its quite well stuck and wont come off unless you twist it quite hard.

The trick with thermal paste / glue / tape is for it to be as thin as possible while providing as much contact as possible, so maximum surface area and just thin/thick enough to fill any dips in the surfaces. But... don't over think it it will work just fine.

 

[joshc]

The original is fine especially if you are not overclocking.

There is no intake fan on a 650 - the power supply fan is the system fan. This is the same as several other Macs and does mean the floppy drive acts as part of the intake and hence gets very dusty.

The 7100, despite using the same case design as the 650, introduced a fan close to the front to help cool the 601 CPU. Something similar could be rigged up for a 650 if you were worried about the temperatures.

 

[Byrd]

A tiny thin layer of any good quality thermal goop, with a small amount wiped away on two opposing corners + tiny blob of superglue has been my go to way to mount heatsinks on '040 CPUs for years. It can be easily removed by putting the CPU in the freezer for 30 mins (wrapped up in a couple of antistatic bags, sealed), removing CPU and using a razor/screwdriver to pop off.

Thin thermal tape is also another option (cut to size), but I find it dries out more quickly than proper paste.

 

[egrath]

There are various kinds of heat conducting tapes. The ones whiche are thicker (0.5 - 1.0 mm), they sometimes can dry out - they are also often called 'Heat conducting Pad'. Personally i prefer the thinner ones, called 'Heat conducting Foil' which are extremely thin (0.125 mm). Don't know what they are made out from, but they never dried out or changed their thermal behavior even after years.

Can recomend the following product:

Thermal Management - Klebebänder - wärmeleitend, elektrisch isoliert - KERAFOL

Die KERATHERM®-Klebebänder sind wärmeleitende und elektrisch isolierende doppelseitige Klebebänder. Sie verfügen über ausgezeichnete, dauerhafte Klebkraft mit sehr hohen Wärmeleitfähigkeiten bei gleichzeitig sehr guten Isolationseigenschaften.

www.kerafol.com

(KL 90)