Buying Conundrums: Intel Core i7 920 versus i7 930
When it comes to building a high-performance PC, at the moment there's just no competition for Intel's Core i7 CPUs; in comparison to Nehalem, however much tweaking AMD does to its K10 architecture, it's clearly running on empty.
When it comes to choosing which Core i7 CPU to buy though, there's a bit of a debate as to whether it should be the i7-920
or the i7-930
The two chips are very, very similar - in fact, if you take a look at the table below, there really is only one difference, which is the fact the 930 runs 133MHz quicker, at 2.8GHz. This speed increase comes from a higher multiplier, not bus speed, so there's no additional memory bandwidth either.
|CPU||Core i7-920||Core i7-930|
|Configuration||20 x 133||21 x 133|
|Number of cores||4 x physical, 4 x logical||4 x physical, 4 x logical|
|L1 cache||32KB L1 data, 32KB L1 instruction per core||32KB L1 data, 32KB L1 instruction per core|
|L2 cache||256KB per core, inclusive||256KB per core, inclusive|
|L3 cache||8MB accessible by all cores, inclusive||8MB accessible by all cores, inclusive|
Otherwise, the 930 and 920 are virtually twins - they're both made using the same D0 stepping. Intel (and AMD) do make small changes to CPU designs that they don't designate with a new stepping code, but performance wise, when we tested the 930, we found it had only a very slight advantage over the 920: Crisis ran at exactly the same minimum and average frame rates on both CPUs. Thanks to its more complex geometry, X3: Terrain Conflict ran slightly faster on the i7-930, but only by around 2-3fps.
The real difference was when it came to overclocking; our 930 overclocked much better than any of the 920s we've had in the labs. With its vcore boosted to 1.45V, the QPI raised to 204MHz and Turbo Boost disabled, we were only able to overclock the i7-920 from 2.66GHz to 4.08GHz.
In contrast, the i7-930, using exactly the same voltages, but with a CPU multiplier of 21x and QPI of 205MHz, was happy to run for hours on end at 4.3GHz. At 4.3GHz, the i7-930 returned markably better benchmark results than the overclocked i7-920.
All this was enough for us to start recommending the 930 in our Buyer's Guide
, but this was based on the fact we expected the 920 to go end of life quite quickly. As it turns out, availability of the 920 is still pretty good, and what's more, the 920 is a lot cheaper than the 930. You can pick up a 920 for around £170 for the usual UK retailers, whereas the 930 will set you back £60 more, around £230.
So the question is, which should you buy? Firstly, we should say both are good CPUs that offer terrific performance, and neither one is a bad buy. However, not everyone wants good, especially when building a Core i7 PC - you want the best
, so which is it?
Well, we should start off with the easy scenario: if you're not going to overclock, get the i7-920 and save yourself the money. The 133MHz extra speed of the 930 makes practically no difference.
If you're only going to be going for a moderate overclock - let's say 3.8GHz or below, then again, we'd say go for the i7-920. None of the 920s we've seen have struggled to hit this speed on air-cooling (although, as always with overclocking, your mileage may vary) and you can pocket a decent amount of cash.
Above 3.8GHz, then you should look to the i7-930. While 920s can often hit 4GHz, the 930 gives you more headroom, or the capability to go far further in terms of speed.
If you're water-cooling, we'd also say that the i7-930 should be your chip of choice, again, thanks to its superior overclocking potential. After all, if you're going to all the trouble of plumbing in your PC, it would be rude not to clock the speed up.
Of course, as the 920 is officially an end-of-life product, the problem of which cheap Core i7 to buy isn't going to stick around for a long time - the longer you wait, the more likely it will be that the i7-930 will be the only game in town.