20Celcius difference between CPU A and B when transcoding with Handbrake

[Mejenborg]

Hi.

So, I just had an issue with my upgraded Mac Pro 5,1, revious a 4,1 with 2xE5520 now 5,1 with 2xX5690, where I had to take the CPU's out and reinstall them again.

I'm fairly convinced that I've used the proper amount of heat paste, it's definitely not my first time installing CPU's. In idle mode there is a 8-11 degrees celcius difference between CPU A and B, where A is the hottest at about 40-45 degrees.

But when I transcode with the latest Handbrake release, CPU A max out at ~80 degrees celcius, but CPU B runs at ~60 degrees.

I never really thought of looking at the CPU temperature differences before now.

Is this normal? Or is there something to be done?

 

[orph]

hi im a tad confused is it a macpro 5.1 or 4.1 or 4.1 firmware upgraded to a 5.1 or a 5.1 with a 4.1 cpu tray?

if it's a 4.1 did you correctly install the cpu's ?
did you have problems before you upgraded the cpu's?

 

[TzunamiOSX]

CPU A is the rear CPU. The rear CPU is always hotter, because a part of the hot air from CPU B (front) and bridge is blowing through CPU A.

 

[Mejenborg]

hi im a tad confused is it a macpro 5.1 or 4.1 or 4.1 firmware upgraded to a 5.1 or a 5.1 with a 4.1 cpu tray?

if it's a 4.1 did you correctly install the cpu's ?
did you have problems before you upgraded the cpu's?

I have upgraded the firmware and the CPU's. As mentioned, I'm pretty sure I've installed them correctly. pea sized thermal paste and so on. Never had CPU overheating issue on previous PC builds. Before posting this, I tried to remove the heatsink and changed out the thermal paste and reapplied new paste, but with a tiny amount more, and installed the heatsink again. Same "issue".. Don't know whether it's normal, or an issue..
[doublepost=1486361512][/doublepost]

CPU A is the rear CPU. The rear CPU is always hotter, because a part of the hot air from CPU B (front) and bridge is blowing through CPU A.

Yah, my thought exactly.. That explains the 8-11 degrees difference in idle, but when the difference reached ~20 degrees, I got a bit worried.

My initial thoughts was that handbrake wasn't able to use both CPU's, but can't find evidence of that on any forum.

I'm going to test with some Blender 3D rendering to see if that will give me a different result.

 

[orph]

so it's a 4.1 firmware upgraded to a 5.1
did you correctly install the cpu's ? did you de-lid them or use washers for spacing ?
(you cant just drop in cpu's in a dual 4.1 without some extra work as there designed for de-lided cpu's so the spacing is off for normal cpu's)
a 20c delta seems high, but i dont know dual cpu macpros well so some one will have to confirm.

 

[Mejenborg]

so it's a 4.1 firmware upgraded to a 5.1
did you correctly install the cpu's ? did you de-lid them or use washers for spacing ?
(you cant just drop in cpu's in a dual 4.1 without some extra work as there designed for de-lided cpu's so the spacing is off for normal cpu's)
a 20c delta seems high, but i dont know dual cpu macpros well so some one will have to confirm.

Nope. Don't have the guts to de-lid US$500 worth of CPU's. So I've applied some thermal pad for the spacing between the logicboard sensors (or whatever they are) and the heat sink and mounted the heatsink carefully on the CPU.

 

[orph]

so you followed a guide (which one, link if you can) did you correctly use spacers to on the heat sink or count screw turns?

 

[Mejenborg]

so you followed a guide (which one, link if you can) did you correctly use spacers to on the heat sink or count screw turns?

I've read a lot of others experiences with upgrading 4,1 to 5,1. But my major influence was this guy.

[doublepost=1486364446][/doublepost]I might purchase some thermal paste, after 3 remount sessions I've run out, and then reinstall the original Xeon E5520 to see if there's a ~20 degrees difference when transcoding handbrake.

 

[orph]

iv not done a dual cpu upgrade so will be worth waiting a bit till you get a reply from some one ells who has.

i know 10c delta is normal ish but 20c sounds a tad high

be good to hear from some one with more experience in it.

the video looks ok, so you used the count the turns one

ps can you post a screen shot of the temps both at idle and working on an encode

 

[pastrychef]

I used to see similar temps on my old MacPro5,1 when using Handbrake. From all that I read, it's pretty normal for the 4,1s and 5,1s with 130W CPUs. Mine used to reach the limits of what Intel recommends as max temps and I eventually had to use SMC Fan Control to increase fan speeds.

 

[TzunamiOSX]

Ok, on my test with Handbrake (threads=18 setting)

CPU A 83°C
CPU B 61°C

This is totally normal. Hotter CPU B, hotter air coming to CPU A, much hotter CPU A.