IBM Thinkpad A31p cpu support

[Xyra]

Bios link: http://download.lenovo.com/ibmdl/pub/pc/...uj14ud.exe
The Thinkpad A31p uses the Intel i845 Mobile DDR Chipset.

I would like to have support added for three Mobile Pentium 4. Would like to find out if it is possible to upgrade Thinkpads A31p to a newer spec P4 than the first Pentium 4-M with 400 fsb.
Thinking that I could put up my own A31p as a testbench for this purpose
The following Mobile Pentium 4 cpus uses Hyper Threading and have 533 fsb compared to the older P4-M.

SL726, SL77R and SL7NC.

I've looked for a donor-bios but not found any among the IBM Thinkpads that uses any newer Mobile P4 cpu than the P4-M with 400 fsb. It seems like IBM went straight to the Pentium-M / Centrino from there.