Mac Pro: The perfect workstation
With more than double the memory throughput of an eight-core, 3GHz Xserve, the massively parallel Nehalem-based Mac Pro is built to rock your world
These machines establish a new bar in the price/performance/watt trifecta. In its factory configuration with one hard drive and the Nvidia GeForce GT120 GPU, the 2.26GHz eight-core Mac Pro's peak power utilization of 240 watts plummets to around 120 watts at idle. I was extremely impressed by OS X's broad and frequent adjustments to power draw during burn-in tests that overcommitted CPU resources. On prior Intel Macs, there was a direct correlation between gross core utilization (as reported by Activity Monitor) and power draw. The Nehalem Power Mac breaks this relationship.
In the Nehalem Mac Pro, the mix of workload determines the power consumed. Even while all 16 logical cores stayed locked at 100 percent utilization, the Mac Pro would drop power draw by 20 to 40 watts as workload combinations shifted.
STREAM is the industry's accepted standard benchmark for memory throughput, but it serves well to test the efficiency of the bus between processors in NUMA (non-uniform memory access) architectures like Nehalem. Each Nehalem CPU has an on-board, triple-channel memory controller that drives a dedicated bank of DDR3 memory. If one CPU needs access to memory attached to the other CPU, it has to go across the inter-CPU bus. With a sound NUMA implementation and a NUMA-optimized OS, aggregate memory throughput should increase with the number of CPUs engaged in an operation.
That's the case with the Mac Pro. I configured STREAM to run its tests on a 1.8GB array of memory. On the 2.93GHz Nehalem Mac Pro, hitting that array with one thread derived a "Triad" throughput score of 8GBps. Running STREAM again with eight threads pulled the second CPU into operation and the Triad score rose to around 20GBps. For contrast, the STREAM Triad scores for the non-NUMA 3GHz eight-core Xserve are 3.4GBps for a single thread and 7.4GBps for eight threads.
Mac Pro highlights