The basic outlines of the plan now seem to be clear. In early 2005, the 600-series P4s will arrive, with 2MB of L2 cache and running at speeds from 3.2GHz to 3.8GHz with an 800MHz front-side bus. From there, though, things get murky. DigiTimes says the 700 series, formerly expected to become the home of Pentium 4 Extreme Edition models, will be likely supplanted by the 600 series, while The Inquirer says the current 500-series products will coexist with the 600s. DigiTimes also claims Intel will introduce two new P4 Extreme Edition processors running at 3.46GHz and 3.73GHz on a 1066MHz bus.
Now, I suppose these rumors aren't mutually exclusive, but I'm dubious about whether all of them are correct. For one thing, I'd be surprised to see Intel introduce a faster bus speed solely for the Extreme Edition processors, especially because the faster bus will supposedly require a new spin of the 925X chipset. I can't recall Intel having introduced a faster bus speed without moving the bulk of its Pentium 4 lineup to that bus frequency in relatively short order.
Keeping a slower bus and adding more cache is a time-honored means of boosting an aging CPU line, but it's uncharacteristic of Intel's handling of the Pentium 4. The slower bus also seems like a big change of plans in light of the fact that the 900-series chipsets support dual channels of DDR2 memory running at 533MHz. As we saw in our review of the Abit AA8, the P4 needs a bus faster than 800MHz in order to best take advantage of DDR2 memory, as simple math would suggest. The 915/925X Express chipsets have a memory architecture that cries out for faster front-side bus speeds, and it's hard to imagine a faster bus wasn't part of Intel's plan for the relatively short term.
Perhaps the apparent decision to change plans by moving to a larger cache and sticking with an 800MHz bus was prompted by some technical difficulty achieving 1066MHz bus speeds consistently. We've already seen Xeon bus speeds linger at 533MHz for a long while due to technical limitations.
If so, maybe the 1066MHz bus really will become a limited-edition feature, or maybe the tentative demise of the 700 series means the end of the P4 Extreme Edition CPUs. The 600-series P4s could simply supplant the Extreme Edition as Intel's "premium" desktop processors, constituting a whole line of higher-priced choices instead of just one uber-low-quantity boutique product. There does seem to be considerably more leeway for marketers to futz with the product mix now that Intel has moved to a model numbering scheme. We'll have to watch and see what happens next.