8-core Mac Pro vs 4-core Mac Pro—compute intensive tasks

See the discussion below on why the 8-core Mac Pro is often no faster than the 4-core Mac Pro (or even slightly slower).

Rob at barefeats.com ran diglloydTools test-compute-speed, a CPU-intensive benchmark that assesses the scalability of multiple processor cores. The results show that the 8-core Mac Pro can be twice as fast as the 4-core Mac Pro with compute-intensive tasks:

4-core Mac Pro @ 3.0GHz	8-core Mac Pro @ 3.0GHz
Test size = 128MB... Chunk Size K MB/sec 1 138.8 2 144.4 4 147.5 8 149.1 16 149.9 32 149.9 64 149.1 128 149.1 256 149.2 512 149.2 1024 149.2 Best chunk size: 16K Testing using 4 threads... thread 0: 147.6...150.2 thread 1: 148.5...150.1 thread 2: 148.1...150.2 thread 3: 147.6...150.2 Aggregate rate: 601MB/sec	Test size = 128MB... Chunk Size K MB/sec 1 138.9 2 144.9 4 148.1 8 149.7 16 150.5 32 150.3 64 148.9 128 149.0 256 149.1 512 149.0 1024 149.1 Best chunk size: 16K Testing using 8 threads... thread 0: 150.2...150.5 thread 1: 150.3...150.5 thread 2: 150.1...150.6 thread 3: 150.3...150.6 thread 4: 150.3...150.4 thread 5: 150.1...150.4 thread 6: 150.1...150.4 thread 7: 150.1...150.4 Aggregate rate: 1204MB/sec

4-core Mac Pro @ 3.0GHz

8-core Mac Pro @ 3.0GHz

Test size = 128MB...
Chunk Size K MB/sec
1 138.8
2 144.4
4 147.5
8 149.1
16 149.9
32 149.9
64 149.1
128 149.1
256 149.2
512 149.2
1024 149.2
Best chunk size: 16K

Testing using 4 threads...
thread 0: 147.6...150.2
thread 1: 148.5...150.1
thread 2: 148.1...150.2
thread 3: 147.6...150.2
Aggregate rate: 601MB/sec

Test size = 128MB...
Chunk Size K MB/sec
1 138.9
2 144.9
4 148.1
8 149.7
16 150.5
32 150.3
64 148.9
128 149.0
256 149.1
512 149.0
1024 149.1
Best chunk size: 16K

Testing using 8 threads...
thread 0: 150.2...150.5
thread 1: 150.3...150.5
thread 2: 150.1...150.6
thread 3: 150.3...150.6
thread 4: 150.3...150.4
thread 5: 150.1...150.4
thread 6: 150.1...150.4
thread 7: 150.1...150.4
Aggregate rate: 1204MB/sec

If you’re a scientist performing intensive calculations which don’t involve much memory or disk access, you’re likely to see a huge benefit from the 8-core Mac Pro. But when working with images or video or sound, large amounts of memory are accessed, and thus performance gains are likely to be modest, or even degraded in some cases.

At a 20% premium over the 3.0 GHz quad-core Mac Pro, and a 48% premium over the 2.66 GHz quad-core Mac Pro, most users will still find the 2.66 GHz model to be the “sweet spot”.

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8-core Mac Pro vs 4-core Mac Pro—compute intensive tasks