Poor GPU performance with 3,1

tpivette89

macrumors 6502
Original poster
Jan 1, 2018
486
250
Middletown, DE
I have a cMP 3,1 with a HD Radeon 7970 GPU. CPUs are a pair of X5272s (2-core at 3.4ghz), RAM is 16GB at 800mhz (8 x 2GB). Running 10.11.6 on a SSD using one of the SATA II drive bays. For monitors, I'm running a pair of ACD 23" aluminum versions.

Running Unigine Valley on high settings (not Ultra), I'm only averaging around 27fps. With the same card on my 4,1 (flashed to 5,1) I get an average framerate of 50fps... however, that is a 12 core machine with more RAM (24GB).

What is keeping the GPU from reaching the performance figures I know its capable of? Is there something I'm missing or lacking?
 

Ludacrisvp

macrumors 6502a
May 14, 2008
686
301
I find it interesting you are running dual dual core processors in the 3,1 ... curious why you have that config. Was it just to get 3.4 GHz vs 3.2?

Anyways for the GPU it is probably because the 3,1 isn’t running the GPU with PCIe 2.0 x16 and is probably doing 1.1 or 1.0.
 

tpivette89

macrumors 6502
Original poster
Jan 1, 2018
486
250
Middletown, DE
I find it interesting you are running dual dual core processors in the 3,1 ... curious why you have that config. Was it just to get 3.4 GHz vs 3.2?

Anyways for the GPU it is probably because the 3,1 isn’t running the GPU with PCIe 2.0 x16 and is probably doing 1.1 or 1.0.
I just wanted to see if these CPUs worked in the 3,1 Mac Pro (originally when I got the machine, they were not included on the compatible list). Plus, yes, I wanted the better single core scores... but now realize that the difference between the 3.4 vs the 3.2 in single score is basically negligible.

Why would it not run PCIe 2.0? Is this something that has only happened recently due to the new 138 firmware? Or is it a limitation of the 3,1?
 

Fl0r!an

macrumors 6502a
Aug 14, 2007
906
526
Ther's a known power management bug when running GCN GPUs in a 3,1. A workaround is trashing AppleIntelCPUPowerManagement kexts. There's more information on this topic here and on netkas.org.

Additionally, the GPU will be CPU-bound due to quite slow single core performance of those CPUs.
 
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