Appearance and specs.There's more to cloud the issue. It makes implicit sense to assume that a die shrink (0.09-micron) and accompanying voltage reduction (~1.4v) would lead to a cooler-running processor. What that doesn't take into account is that heat is now concentrated in a smaller area. 125 million transistors, amongst other processor hardware, occupy a space of no more than 112mm². Our research has shown that a 3.4GHz Prescott runs at up to 12c warmer than an equivalent Northwood. Intel's own figures quote a <100w TDP (Thermal Design Power). It's a warm processor, no doubt about that.
There's nothing to distinguish our sample 3.4GHz semi-unlocked Pentium 4 Prescott from any other. For the record, the CPU had multipliers available from 14x through to 17x (default). As with all later Northwoods, it runs off a native 200MHz FSB.
Socket 478, but for how much longer?. We're adamant the 3.4GHz model will be the last. Socket 775 is all set to go, with improvements to the core logic affording a touch extra performance. For now, though, Prescotts will function on most S478 motherboards. It's up to motherboard manufacturers to release compatibility BIOSes.
Larger L1 and L2 data caches are an obvious difference, so is the reported 0.09-micron manufacturing technology. CPU-Z can only tell you so much. On reflection, there's enough difference between Northwood and Prescott cores to warrant a separate review in itself.
Associativity, or degree of relatedness is up. So is latency, apparently.
Let's sum it up in a table.
|Name||Pentium 4 3.4GHz Prescott||Pentium 4 3.4GHz Northwood||Pentium 4 3.4Ghz Extreme Edition||Pentium 4 3.2GHz Prescott||AMD Athlon 64 Model 3400+||AMD Athlon 64 FX-53|
|FSB||200MHz quad pumped||200MHz quad pumped||200MHz quad pumped||200MHz quad pumped||2200MHz (core speed)||2200MHz (core speed)|
|Pipeline length||31 stage||20 stages||20 stage||31 stage||12 stage||12 stage|
|Socket||S478 (for now)||S478||S478||S478 (for now)||S754||S940|
|Transistor count||125 million||55 million||169 million||125 million||106 million||106 million|
|CPU die size||112mm²||127mm²||237mm²||112mm²||193mm²||193mm²|
|Voltage||~ 1.375v||~1.525v||~ 1.525v||~1.375v||1.5v||1.5v|
|Memory support (now)||DDR400 DC||DDR400 DC||DDR400 DC||DDR400 DC||DDR400 SC||DDR400 DC Registered|
|Other||SSE3, HT, Higher L1 data cache associatively||Last Northwood||2MB L3 cache Expensive||SSE3, HT||On-die controller||32/64-bit|
* - The Pentium 4 Northwood has 8kb of L1 data cache (4-way associativity) and 12kuops L1 trace execution cache. The Prescott has 16kb of L1 data (8-way associativity) and the same 12kuops. The question that's been on our lips is whether the Prescott's technological advantages can make up for the performance shortfall that a much longer pipeline will inevitably create. We're about to find out.