Alright, well...resurrection of a very old thread, but likely not quite in the way everyone would think...this is *not* just a bump!
Having been dealing with this -exact- problem on my A25 series laptops, I have a good portion of an answer for you.
The A25's (and quite likely the A30's as well) were 'desktop replacement' systems...ie, they can and DO use full-powered desktop Pentium 4's, using the pga478 socket (the 479 socket someone else was thinking of was something done for the Pentium M's, which had a higher bus speed, to differentiate...the pin out is also slightly different so that you cant use the processors interchangeably...interestingly though, mobile Core 2 Duo's run on a 478 socket that is IDENTICAL to the p4's...but they can be hard to get back out, so be careful if you're getting curious like I did that you don't get the core2 stuck in the damn thing hehe).
So, having in my possession an A25-S207, A25-S208, A25-2307, and A25-S3072...
The systems themselves all use the exact same motherboard, and bios...but there's a catch...in trying to mod the bios's to allow for extra support (as they will happily take a P4 2.4/512/800 HT), there is something inherent to each system that prevents a HIGHER processor from being used...ie, I can't just put a 3.06/512/400 from the S3072 into the S207. There is NO REASON why the newer processors shouldnt work (and trust me, Im going into all sorts of lengths to figure this out and eek a little extra L2 cache out...not that I wouldn't -love- to put in my spare Gallatin (3.2/2m/800) if I could. Aside from the physical differences in the chips (if you flip them over, you can see the patterns and numbers of transistors on the bottom of the chip increase and change).
For all intents and purposes - this should be controlled by CPU microcode in the BIOS...however, I can find neither a tool to help me solve this, nor can I seem to find the appropriate header within the bios via hex editor to actively update the microcode within it...I am beginning to wonder if there is a second flash chip which actually holds the microcode and all it does is reference what's there...however, should I find the answer to this, I shall let people know (probly in here), the same as I will let everyone know on the Bios modding forums I have recently joined to find information and resources to do this with, as I believe we should be able to upgrade our systems to what they CAN do, not what manufacturers want to allow us to do before they want to force us to buy new systems.
Again, I realize this is long outdated, but figured I'd share the information in case anyone else came across this issue as I have, and thus ran across this same forum post as a result, as I did.

Stupid Toshiba! lol