I've also been wavering around an Abit/P4A/RDRAM system, and trying to find out as much as I can. My understanding is that the answer to your last question is that 16 device RDRAM should overclock better than 8 device; I gather the number of devices relates to the number of memory chips and that the denser chips may have less margin (probably being the same reason that most recommend 256 Mb sticks rather than 512 Mb sticks). Many people also seem to believe that Samsung RDRAM is better than the others -- even if the others are using Samsung chips! So I guess Googlegear's a good place to go for RDRAM.
Although you didn't specify, I'm guessing that your Abit motherborad choice is the TH7II or TH7II-RAID. This is also the motherboard that I would like to get, however it seems to have several potential downsides that you should be aware of:
First, people still seem to getting THII7 boards with version 37 BIOS which does not (fully) support the Northwood. Some people seem able to get the boards to boot up (although their operation may be a bit squirrely) and are then able to flash to the new version 38 BIOS that does support the Northwood. Unfortunately, others with the version 37 BIOS get hung up with an error "29" before the boot is complete, which leaves them short of the point where they can flash to version 38. The options for the unfortunate are to either find someone with a 256k cache 478-pin P4 that they can borrow to boot with and then flash BIOS, or get a new BIOS chip from Abit. Those going the latter route have reported that Abit charges them for the chip and for shipping (~$15). I suppose you could also try to RMA the board. I was hoping that all these older boards would be quickly washed out of the system, but here's an interesting note posted by Googlegear on their TH7II: *Important Note: This motherboard has the potential to support the new Skt478 P4 "Northwood" (512K cache) processor, however it may need a BIOS flash to do so. Unless you are highly experienced with flashing a BIOS, we recommend that you purchase a motherboard that definitely supports the P4 "Northwood" instantly--(on our website these boards have "Northwood" listed in their titles). Flashing a BIOS can easily go bad, resulting in a ruined motherboard and voided warranty. This doesn't seem promising...
Second, some TH7II boards have DRCG chips that can not reliably support overclocking beyond 400 Ghz. There have been some posts about how you can tell these chips apart. I gather that if the first line starts with ICS, then if the second line ends in -03 it's the 500 GHz; if it's -13 then it's the 600 GHz. And if chip label ends with CYP, it's the 400 GHz chip. Anyway, an overclock to 133 GHz FSB dictates 500 GHz at least. I've been told by more experienced members that the newer boards have the 600 Ghz chips, but one has to wonder how many of the older 400 GHz boards are still sitting on supplier's shelves...
Third, older TH7II boards have AC97 sound, while newer boards have AC2001. Same issue on what the TH7II I receive might have...
With all these unknowns out there, ordering one via mail seems a bit like Russian roulette! How can I be sure to get a new board with version 38 BIOS, the -13 clock generator chips, and the AC2001 sound? I would really like to look the board over before I buy it, but there's no one locally who carries Abit (not even Frys). What to do?
XboxLPU, if you (or anyone else out there) has worked through this already, please let me know!
P.S. -- I see that the TH7II has an on-board LAN option that I've never actually heard that anyone has. Anyone?
THANKS!