The mobile versions are usually just hand-picked examples which run happily on lower Vcore, so they consume less power.
they're just slightly higher quality examples of the chips basically.
Same as Normal Athlon XP 'Barton' chips and the Mobile XP chips. Overclockers love them because they overclock much better than 'normal' Desktop chips (plus they have unlocked multipliers so the laptops can throttle them down to save more power - not sure if the same is true of the 754 variants but I would suspect so to some extent)
The 'Clawhammer' A64 Chips have 1MB L2 Cache, whereas the 'Newcastle' A64 Chips have 512K Cache. It's also important to note the differences with certain models, like the 3400+ Clawhammer is 2.2Ghz w/ 1MB L2 and the 3400+ Newcastle is 2.4Ghz w/ 512K L2...as far as I understand it the 200Mhz speed boost is better than more Cache
AMD Athlon XP 2100+ stock
Asus A7N8X-E Deluxe
1GB generic RAM
ATI Radeon 9700 Pro 360/335
DTR is SLIGHTLY handpicked...but more importantly it doesn't have an IHS. Except in a few rare cases, you can't use the standard mounting bracket with it (no contact); you also have to be a lot more careful not to crack the core when installing it.
Maxtor disgraces the six letters that make Matrox.
No one mention it, but the DTR and Mobile A64 don't have an heatspreader on the CORE. This make them more "fragile" to heatsink installation, but on the other hand, this ensure a better contact between the CORE and the heatsink. For overclocking, it's a good thing, you can suck a bit more heat from the core!
With zalman's, watercooling, some coolermaster coppers, really such a need for slightly more heat dissipation is not at all worth the 70+ dollar difference, plus, the chance of losing it all to a snaped core. I havent bothered with amd after k6-III 400 as the chance of snapping my cpu was high and thats just a retarded design flaw. Finally, I think they are back into their senses.
I've installed Loads of Athlons (3 of my own, 3 for friends/family, 5+ at work) without heat spreaders and <i>never</i> cracked a core. The risk is hugely overstated. unless you're a heavy-handed sausage-fingered idiot it's quite difficult to do. And that's not even counting all the times I've removed and replaced my own heatsinks....
Actually, we used to have a heavy-handed sausage-fingered idiot working here and even HE managed to put together a couple of systems without damaging them.