What is the fastest processor that will work with the socket 478? I currently have a 2.8ghz p4 with a 512k l2 cache.. Manufacturer: Dell computer corporation Model: Optiplex gx270 OS: Microsoft Windows XP Home Edition CPU/Ram: 2.793 GHz / 1022 MB Video Card: ATI Radeon 9600/9550/X1050 Series

The good ol' Socket 478. The fastest processor is the 3.4 GHz Pentium 4 Extreme edition. After that is the 3.4 GHz Pentium 4... ...then the 3.2 GHz Celeron D... ...and the highest-clocked lowest-end processor for the 478 is the 2.8 GHz Celeron. If you go to eBay, you might be lucky and get a P4 Extreme Edition for cheap. Hope this helps, -Trent "If at first you don't succeed, skydiving may not be for you." -Our tour guide at Fenway Park in Boston, MA.

"...then the 3.2 GHz Celeron D..." The 3.2 Cel D performs more like a 2.66GHz/533 P4. The P4 3.0/800, 2.8/800, and even 2.6/800 are faster. There's not much difference in performance between the 3.4 and the 3.4EE. The P4 is a bandwidth-loving CPU; EE's slow L3 cache doesn't do much to increase performance. If you absolutely must upgrade, then get the 3.4 Northwood. However, a better idea would be to wait until you can build/buy a brand new system. Socket 939³ Dual-core Opteron 185 @ 3.2GHz 2x 8800GTS in SLI 4GB CL2 PC3200 Blu-ray burner X-Fi Ti Pro PCI-E Antec P182 Samsung 24" LCD Vista 64

Not worth upgrading.

"The 3.2 Cel D performs more like a 2.66GHz/533 P4. The P4 3.0/800, 2.8/800, and even 2.6/800 are faster." I figured that. I was just giving the OP the highest-clocked variants of all 4 processors for the Socket 478. "If you absolutely must upgrade, then get the 3.4 Northwood..." Wouldn't a similarily-clocked Prescott or Cedar-Mill out-perform the Northwood because of the added SSE3 instructions that the Northwood lacks, or is there something I don't know? -Trent "If at first you don't succeed, skydiving may not be for you." -Our tour guide at Fenway Park in Boston, MA.

"Wouldn't a similarily-clocked Prescott or Cedar-Mill out-perform the Northwood because of the added SSE3 instructions that the Northwood lacks, or is there something I don't know?" In non-SSE3-optimized apps, Prescott is actually slower than Northwood, clock-for-clock. Prescott's 31-stage pipeline just destroys any performance advantage that its larger L2 cache may provide. Northwood only has a 20-stage pipeline. Plus, it runs a lot cooler. Clock-for-clock, Cedar Mill is faster than both Northwood and Prescott, thanks to its 2MB of L2 cache. However, it's only available in the LGA 775 form factor. Socket 939³ Dual-core Opteron 185 @ 3.2GHz 2x 8800GTS in SLI 4GB CL2 PC3200 Blu-ray burner X-Fi Ti Pro PCI-E Antec P182 Samsung 24" LCD Vista 64

Jackbomb, I didn't know that! Thanks for the info! The long pipeline is what handicapped the Pentium 4, especially when, in some apps, a 1.4 GHz Willamette was pitted against a 1.4 GHz PIII Tualatin. Mattg, Based on the fact that the Northwood P4 is the best performer for the 478, and the fact that you already have a 2.8 GHz Northwood, and the fastest Northwood is 3.08 GHz, I would agree with jam and say that there isn't really much farther you can go with a processor for your system. -Trent "If at first you don't succeed, skydiving may not be for you." -Our tour guide at Fenway Park in Boston, MA.