Dunno about your specific mobo but, for example, a P3B-F post rev. 1.03 can use a coppermine P3 or celermine with a bios update (needs 1.004 at least I think). My P3B-F is rev. 1.01, so updating the bios would not work for me in that respect. I suggest you check ASUS' site for specs.
http://www.asus.com/Products/Motherboard/Pentiumpro/P2l97/index.html
http://www.asus.com/Products/Motherboard/bios_slot1.html#p2l97
P2L97 (ATX )
- BIOS Upgrade and Road Map :
lx2i1009.zip
P2L97 ACPI BIOS Version 1009. 11/05/99
Fix Microsoft Pre-OS test failure
Support IDE hard disk larger than 32G bytes.
Fix Russian Y2K test program failed.
Revise Y2K patch.
Fix boot failure with some boot managers installed.
Update Symbios BIOS to Rev 4.12.
No system node report for LPT when it's Setup disabled. (LPT disable in Windows when it's Setup disabled)
Upgrade microcode update for Celeron mA0 stepping (CPUID=660) to revision 0A.
Microcode update upgrade for PII 653, 672, and 673. 653: 00A->010; 672: 00B->00C; 673: 007->00A. *Maybe someone can use this to answer your question; looks like celerons are OK*
Fix serial port failure running Windows 2000.
Add keyboard wakeup item with three choices of key combinations.
Fix FDD Write Protect function failed with 'format a: /u' command.
lx2i1008.zip
P2L97 ACPI BIOS Version 1008. 02/12/99
Add Processor Serial Number item.
Remove CPU L2 cache turbo mode item.
Add new P6 processors recognition. *ditto*
Fix the system cannotboot from 3Com 3C900-TPO LAN card if no floppy is drive attached.
Fix AGP/MDA support failure for AGP Onboard models.
Fix NT 5.0 installation failure for models with PIIX4 ID=7.
Removed parallel port 3BCh/EPP combination.
Remove "disabled" option in ECP DMA item when ECP selected.
Fix Accel Galaxy52 boot failure.
Fix boot virus false alarm for PCI-L101 lan card.