Wed 22 Aug 2012 14:07
Intel desktop CPU price-performance: Hyperthreading not helping?
Typically, CPU prices follow performance. Faster CPUs command higher
prices; slower CPUs are available for less. Recent Intel desktop CPUs
continue to show this general pattern, but there appears to be more to the
story than usual.
At first glance, everything seems to be what you would expect. Using current pricing in US$ at time of writing from newegg.com, we get:
Processor | PassMark | Price | PassMark/$ | Price-Performance vs G640 |
---|---|---|---|---|
Pentium G640 | 2893 | $79 | 36.6 | 100% |
i3-2120 | 4222 | $125 | 33.8 | 92.2% |
i5-3570 | 7684 | $215 | 35.7 | 97.6% |
i7-3770 | 10359 | $310 | 33.4 | 91.3% |
But what happens if we look at a more real-life benchmark? Consider SPEC CPU 2006 Integer (CINT2006) Baseline. For each CPU, I used the CINT2006 Baseline results from the most recently reported Intel reference system, as reported on spec.org. In the case of the G640, no Intel reference system was reported, so I used the results for a Fujitsu Primergy TX140 S1p.
Processor | CINT2006 Base | Price | CINT/$ | Price-Performance vs G640 |
---|---|---|---|---|
Pentium G640 | 34.4 | $79 | 0.44 | 100% |
i3-2120 | 36.9 | $125 | 0.30 | 67.8% |
i5-3570 | 48.5 | $215 | 0.23 | 51.8% |
i7-3770 | 50.5 | $310 | 0.16 | 37.4% |
A look at hyperthreading may provide some answers. Intel hyperthreading is a feature of some Intel CPUs that allow each physical core to represent itself to the OS as two different "cores". If those two "cores" simultaneously run code that happens to use different parts of the physical core, they can proceed in parallel. If not, one of the "cores" will block. The i3 and i7 CPUs offer hyperthreading, the Pentium G and i5 do not. It turns out that the PassMark benchmark sees significant speedups when hyperthreading is turned on. SPEC CINT2006, and many ordinary applications, do not.
What about SPEC CINT2006 Rate Baseline, then? The SPEC CPU Rate benchmarks measure throughput, not just single-job performance, so maybe hyperthreading helps more here? Let's see:
Processor | CINT2006 Rate Base | Price | Rate Base/$ | Price-Performance vs G640 |
---|---|---|---|---|
Pentium G640 | 61.7 | $79 | 0.78 | 100% |
i3-2120 | 78.8 | $125 | 0.63 | 80.7% |
i5-3570 | 146 | $215 | 0.68 | 87.0% |
i7-3770 | 177 | $310 | 0.57 | 73.1% |
What does this mean, then? It suggests the increase in price from a non-hyperthreaded to a hyperthreaded Intel desktop processor may reflect more an increase in PassMark performance than an increase in real performance. Hyperthreading may have a positive effect, it seems, but typically not as much as PassMark suggests. At present, for best real-world price-performance in Intel desktop CPUs, I would consider models without hyperthreading.