Upgrades for Intel PIII 866 - RB80526PZ866256

[Bill]

I'm at a loss for trying to determine what is the greatest possible CPU I can upgrade an old Compaq Presario Desktop PC to.

I confirmed that it's operating with a Intel Pentium III 866 - RB80526PZ866256 (BX80526C866256 / BX80526C866256E).

I'm interested to know either:
A) What is the greatest possible CPU I can upgrade to, or...
B) How to determine my self what's the fastest CPU I can upgrade it to.

I've read that a CPU upgrade is specific to the motherboard however I can't find out anything about the motherboard this is build on. The information printed on the motherboard is:

PWA-ELISE-SWAP BD
PCB 316701200001-R01
ASSY 411701200001 R

[Marcin]

If your motherboard support Tialatin then 1400 Mhz is max in other case you can use max Coppermine 1133 MHz. I'm sorry but I cann't confirm support of Tualatins from details which you provided. Maybe you will try read info from north bridge (chipset) ?

[hugo929]

It is said PWA-ELISE-SWAP BD is an OEM version of MiTAC 6513VX.
In common case, the board of a BRAND PC (I mean not the boards on market) is hardly upgradable because the frequency multipliers is locked to a fixed number.

[Marcin]

So you have VIA Apollo Pro 133A chipset which support to Coppermine 1,13 Ghz. With additional FCPGA->FCPGA2 adapter propably you can use PIII-T 1400 GHz but some "brand pcs" have locked cpu code in bios and gets error with wrong CPU and says hit F1 to continue or in other case blocks boot to media.