John Gillooly becomes a Sempron fiend.
Budget CPUs have served enthusiasts well in the past. From the first days when the Celeron 300A kick-started a little trend called overclocking, to the initial spurt of gaming goodness delivered by AMD's Duron, cheap has not always meant crappy. Sure, Intel's more recent efforts like the crippled Willamette that became its first Pentium 4 Celeron have been woeful, but we still have faith in budget CPUs.
Since AMD launched the Athlon 64 its once top end Athlon XP processors have settled into the budget niche, but AMD has now begun to phase out these CPUs, and in its place has announced the Sempron. Sempron is a class of budget CPUs that spans both Athlon XP derivative Socket A cores and Athlon 64 derivative Socket 754 ones. AMD also plan to eventually launch models for the newer socket 939 motherboards.
In the current range only the Sempron 3100+ uses the Athlon 64 architecture, so it is this that we have chosen to focus on. Even though it uses the same basic 130nm SOI core as the Athlon 64, it has some key differences. The first is a lack of 64-bit support, which could be seen as dramatic in terms of longevity, but the reality is that Windows XP 64-bit is not due until sometime next year. The other key difference is cache. While Athlon 64 CPUs mainly use 1MB L2 cache (some have 512KB), the Sempron 3100+ has 256KB of L2 Cache.
The effect of cache upon performance does depend on the CPU architecture, and from our previous testing of the 512KB cache Athlon 64 we were surprised to see that the halving of cache didn't make a huge difference in performance. The fact that the Athlon 64 architecture moves the memory controller onto the CPU has been the major performance booster for these chips, and they do not appear as cache hungry as Intel's Pentium 4 processors.
To see how the Sempron 3100+ performed we tested it using our Athlon 64 testbench, and put it up against an Athlon 64 3200+. This is not a true apple to apples testing however; the Sempron has a core speed of 1.8GHz, while the Athlon 64 has a 2GHz core. Unfortunately there are no desktop Athlon 64 CPUs running at 1.8GHz. Our testing started with PCMark04 and SYSMark2004, both of which showed a healthy performance lead by the Athlon 64. But these benchmarks emphasise work related tasks, rather than gaming, so we threw Doom 3, AquaMark3 and 3DMark03 into the mix to see whether game performance followed the same trends. While the Athlon 64 was faster, the gap was slighter. In Doom 3 for example there was less than two frames difference between the two processors, and similarly tiny differences appeared in both 3DMark03 and AquaMark3.
So it appears that while it is certainly slower than the Athlon 64, the socket 754 version of the Sempron still performs very well, especially in game. A large part of this advantage is down to the on-die memory controller, something that the other Socket A Sempron models lack. Considering this and the fact that Socket A is an evolutionary dead end, there is no doubt that the Sempron 3100+ is an astonishing budget CPU. It's been a while since the low end of the market gave us something like this, so thanks AMD for reinforcing the fact that 'budget' doesn't have to mean 'cheap'.
Issue: 133 | February, 2012