Clean the old thermal paste, that's usually hard because it's old, but with acetone it should become easier to clean.
And as long as the cooler has enough pressure, you can use any kind of thermal interface you want, these CPUs had a low TDP and that heatsink looks fairly big.
And yes, if you use thermal paste, apply it only on the CPU die, and it doesn't need to be a high quality one, the part you marked in blue, The same for a thermal pad, but the pad needs to be fairly thin, I always used thermal paste. It's like a laptop CPU or a modern CPU without a heat spreader with the die exposed.

You will want to use a thermal paste that doesn't have issues drying out or separating unless you really want to be taking it apart to service it.

While not a paste with a high thermal conductivity by today's standards, Arctic Silver 5 would be a good choice.

My current choice is Arctic MX5 as it has fairly high thermal conductivity and you should not have to worry about it drying out or separating.

For removing, from what I've experienced, Zippo lighter fluid should also work.

I still use Arctic MX-4 tube that I bought like 15 years ago. I just repasted my laptop with it and it's working fine. I also used it on my retro rigs. Remainders of the original thermal pad can be removed with finger nails or plastic.

I like MX-4 too ! It is non-conductive and far better for older parts and has a very long life before drying out IMHO. I avoid all silver based products on nearly all my vintage gear.

I've been using PK-3 and Ceramique 2 with great success.

bogdanpaulb wrote on 2023-04-30, 01:05:

I've been using PK-3 and Ceramique 2 with great success.

Up until recently I had been using Ceramique 2 for stuff that just needed to be repasted and didn't necessarily need a high performance compound.

That is until I repasted my son's Precision 3630 which has an 8700k and the "good" heatpipe cooler.

I had originally repasted it with Ceramique 2 and every time the CPU was loaded (even from the first day it was repasted) the cooler fan would spin up to max speed for a couple seconds and would occasionally ramp up to high speed every once in a while when he was playing games.

I had to take the cooler off when I cleaned the dust out of the system because I couldn't get some of it out with the air blower I was using.

I decided to put MX-5 on it and now the fan doesn't ramp up at all.

No more Ceramique 2 for me for pretty much anything anymore because of that.

cyclone3d wrote on 2023-04-30, 01:59:

Up until recently I had been using Ceramique 2 for stuff that just needed to be repasted and didn't necessarily need a high perf […]
Show full quote

bogdanpaulb wrote on 2023-04-30, 01:05:

I've been using PK-3 and Ceramique 2 with great success.

Up until recently I had been using Ceramique 2 for stuff that just needed to be repasted and didn't necessarily need a high performance compound.

That is until I repasted my son's Precision 3630 which has an 8700k and the "good" heatpipe cooler.

I had originally repasted it with Ceramique 2 and every time the CPU was loaded (even from the first day it was repasted) the cooler fan would spin up to max speed for a couple seconds and would occasionally ramp up to high speed every once in a while when he was playing games.

I had to take the cooler off when I cleaned the dust out of the system because I couldn't get some of it out with the air blower I was using.

I decided to put MX-5 on it and now the fan doesn't ramp up at all.

No more Ceramique 2 for me for pretty much anything anymore because of that.

Had no problems with it for 'normal' applications, for the 'heavy duty' stuff, i use PK-3.

Hoping wrote on 2023-04-29, 19:58:

Clean the old thermal paste, that's usually hard because it's old, but with acetone it should become easier to clean.

It's not thermal paste, it's "phase change material".
When new, it is solid when cold and liquid when hot.
During transportation, it fixes the heatsink on the chip and prevents displacement.
As time passes, it loses its properties and turns into stone.

I just use Thermal Grizzly Kryonaut on everything, can’t be bothered to buy “lesser” paste for older kit, might as well just use one massive syringe for everything, retro or modern.

paradigital wrote on 2023-04-30, 08:07:

I just use Thermal Grizzly Kryonaut on everything, can’t be bothered to buy “lesser” paste for older kit, might as well just use one massive syringe for everything, retro or modern.

Actually regarding Thermal Grizzly Kryonaut, I usually hear too many bad things, like it damages the components and heatsinks, especially on non-copper plates..

https://www.techpowerup.com/forums/threads/da … ryonaut.280141/

deksar wrote on 2023-04-30, 16:21:

paradigital wrote on 2023-04-30, 08:07:

I just use Thermal Grizzly Kryonaut on everything, can’t be bothered to buy “lesser” paste for older kit, might as well just use one massive syringe for everything, retro or modern.

Actually regarding Thermal Grizzly Kryonaut, I usually hear too many bad things, like it damages the components and heatsinks, especially on non-copper plates..

https://www.techpowerup.com/forums/threads/da … ryonaut.280141/

I've seen that kind of scratches with another but cheap thermal paste, the NOX TG10, it is a very bad problem, you can always polish the heatsink to a mirror finish again but the CPU heatspreader no, because you'll erase the marking and it's worst with GPUs exposed dies or with laptop CPUs. And who pays for the damage, because there isn't a perfectly smooth surface anymore with that scratches. I've thought it was because the NOX thermal paste is a cheap, low quality one, but I'm surprised that an expensive one can also cause this problem.

Hoping wrote on 2023-04-30, 16:42:

deksar wrote on 2023-04-30, 16:21:

paradigital wrote on 2023-04-30, 08:07:

I just use Thermal Grizzly Kryonaut on everything, can’t be bothered to buy “lesser” paste for older kit, might as well just use one massive syringe for everything, retro or modern.

Actually regarding Thermal Grizzly Kryonaut, I usually hear too many bad things, like it damages the components and heatsinks, especially on non-copper plates..

https://www.techpowerup.com/forums/threads/da … ryonaut.280141/

I've seen that kind of scratches with another but cheap thermal paste, the NOX TG10, it is a very bad problem, you can always polish the heatsink to a mirror finish again but the CPU heatspreader no, because you'll erase the marking and it's worst with GPUs exposed dies or with laptop CPUs. And who pays for the damage, because there isn't a perfectly smooth surface anymore with that scratches. I've thought it was because the NOX thermal paste is a cheap, low quality one, but I'm surprised that an expensive one can also cause this problem.

I’ll admit this is the first I’ve seen of this “problem”, but I’ve been using my tube for coming up to 5 years now without issue. If it’s a change in recipe thing then I’ll be using something else when the tube is empty, but that’ll be a while as it was a big tube!

I don't want to criticize, it's boring.
It 2 square centimetres of area and a TDP of 30 watts.
Are you seriously discussing the choice of thermal paste?

For reference.
Replacing the fossilized thermal grease on Zalman STG-2 under the heatspreader`s in Tualatin P3-S 1.13GHz reduces the temperature by 3-5 degrees only.

shevalier wrote on 2023-04-30, 17:34:

I don't want to criticize, it's boring. It 2 square centimetres of area and a TDP of 30 watts. Are you seriously discussing the […]
Show full quote

I don't want to criticize, it's boring.
It 2 square centimetres of area and a TDP of 30 watts.
Are you seriously discussing the choice of thermal paste?

For reference.
Replacing the fossilized thermal grease on Zalman STG-2 under the heatspreader`s in Tualatin P3-S 1.13GHz reduces the temperature by 3-5 degrees only.

It's actuallya 17.5W part 😁

Yah, any paste should be fine. Back in the day however, it was considered necessary to shim the cache chips if the thermal pads were removed, due to there being minor difference in height between CPU core and cache packages.

edit: oh wait, this isn't a Katmai is it, got cache inside the CPU.

shevalier wrote on 2023-04-30, 17:34:

I don't want to criticize, it's boring. It 2 square centimetres of area and a TDP of 30 watts. Are you seriously discussing the […]
Show full quote

I don't want to criticize, it's boring.
It 2 square centimetres of area and a TDP of 30 watts.
Are you seriously discussing the choice of thermal paste?

For reference.
Replacing the fossilized thermal grease on Zalman STG-2 under the heatspreader`s in Tualatin P3-S 1.13GHz reduces the temperature by 3-5 degrees only.

I see your point, you're right, but well, we're overall exchanging the ideas and learning (at least, me) here..
The main topic not really was thermal paste brands actually, but a "thermal pad vs thermal paste comparison" for such slot CPUs.

I'm in a small town here and I don't really have thermal paste around me/any stores,
but I do have a Pullsar Ice Dragon Thermal Pad - 1.5mm - conductivity: 17.0 W / mK (https://www.pullsar.de/index.php/product/19/)

Just wanted to learn if such kind of thermal pads would be enough for those CPUs? And specifically; Would 1.5 mm be too thick?

Thanks.

deksar wrote on 2023-04-30, 18:14:

Would 1.5 mm be too thick?

Pads of this thickness are used to fill voids.
For example, between the video card memory and the heatsink.
"Anything but air"
Under the south bridges usually put 0.2-0.5mm.
Under the northern - either paste, or material with a phase change.
For 20 watts, all the same, paste would be better, or a very thin and expensive pad.