X58 can provide up to 36 lanes of PCIe. P55 can only provide 16. These lanes are critical in providing enough bandwidth for the card to receive the huge amounts of data they require; having too few causes the card to choke or "bottleneck," meaning that card sits doing nothing for one or more processing cycles while waiting on more data.
Multi-GPU/SLI: X58 Micro has two x16 lanes, while the P55 can only provide x8 per lane. You can buy one of EVGA's more sophisticated P55 boards that has an NF200 to provide additional lanes, but this extra chip increases latency (sometimes cancels the benefit of the extra bandwidth) and generates extra heat. These "upgraded" P55 boards therefore still have a hot chipset (X58 boards have a northbridge generating heat, non-NF200 P55 boards do not require one) and they also cost a lot more than what is otherwise a budget-friendly P55 lineup; high-end P55s are on par with mid-range X58 boards. In terms of sheer multi-GPU performance, X58 is without question the better performer because it provides high bandwidth with low latency natively. HOWEVER: in your particular case, 460s do not use more than 8x bandwidth, so for right now the difference between x8/P55 and x16/X58 is zero or negligible... But the higher-end Fermi (ex: overclocked 480) and top ATI cards (5970) do use more than x8, so if you upgrade to anything above the 460 in the future you will definitely want X58.
General Pros/Cons: The P55 platform has a wider range of affordable CPU options. There are dual-cores, quads, duals and quads with hyperthreading... Basically, you can get the same CPU performance with any i7 1156 as you could with an i7 1366, although the 1156 CPUs actually have much more aggressive Turbo functions (for example, an i7 920 might gain 200MHz on 2 cores, while an i7 870 gains 600MHz... my numbers are a little fuzzy but close). The only area where X58 is undisputably better in CPU performance is if you run extremely multi-threaded apps and can utilize the $1000+ 980X with its 6 cores and 12 threads. More mainstream versions of this chip are sure to follow, but looking at past Intel lineups, you'll probably still be looking at a $500 investment or more for several quarters, and by the time the really mainstream 6-cores are here, there will most likely be a refreshed CPU architecture or socket out. (Maybe 6-cores will migrate to P55 anyway, I haven't followed the rumors that closely.)
Memory: the extra bandwidth provided by tri-channel over dual-channel is extremely limited. Except for programs designed to really utilize it (such as.... memory benchmarks, lol) you will see perhaps 1-5% performance difference. I had an X58 with 1866MHz 3x2GB, and now run LESS and SLOWER dual-channel 1600MHz 2x2GB and don't notice any difference in everyday use or games, other than with my Windows Pagefile/virtual memory turned off some programs complain about running low on memory. You could simply get an 2x2GB + 2x1GB or a simple 4x2GB kit to match or exceed X58 in this regard. Both boards ultimately allow you to install very large quantities of RAM, so I wouldn't consider either to really be better/worse. Some of the 1156 CPUs do have weaker memory controllers (such as the i3 lineup) and some of the P55 BIOSs do not allow high memory dividers (meaning you must overclock your CPU to get your high-speed memory to run at its factory specs... believe this is true for 1600 and above depending on board and BIOS). But, again, the difference in DDR3 speeds very infrequently provides more than a few percent performance increase and is more useful for benchmarks. The Core CPU lineup just simply doesn't benefit from higher bandwidth after a certain point, which I would argue is around 1300-1500MHz.
To summarize... if you plan to keep the 460s awhile and don't want a massively-threaded CPU, get the P55. If you plan on higher-end cards or want the ultimate benchmark CPU, get X58.
post edited by warthorn - 2010/10/11 09:29:57
