Updating BIOS Q

I have a P4C800E-Deluxe mainboard laying around and I am thinking of using
it for a new build. I almost have enough spare components to make a full
box. Currently I only find P4 478 pin processors 3.0 or better in the
"Extreme", Prescott variety for sale retail. The old processor was a 3.0
Northwood. Asus says that this board will run Prescott processors with a
BIOS upgrade.
My question is: when is the best time to upgrade the BIOS? After you first
fire it up and before you install an OS? Or after? I would intend to use the
AFUDOS [sic] floppy upgrade method using a boot disk made on another puter.

Another, slightly dumb Q (I used to know this): Is the optimum (compatible)
RAM determined by the mainboard/chipset or by the processor?


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