I still use an older ASUS mainboard P2L97 with latest BIOS 1010 beta 004.
A few days ago I bought a Celeron 600MHz for a very cheap price. This PGA390 Socket CPU comes with a Slot-1 Adapter. During BIOS phase I see an error message:
<Bios:> BIOS update data incorrect (CPUID=00000683). Update not loaded.
Win98SE starts without any problem but every WINNT-based system hangs during startup. Unfortunately ASUS has dropped support for the P2L-series mainboard. ...

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