roffle, are you using a HP Pavillion 6640C? If so, then the answer is Yes!
I have reports from several HP 6640C users indicating that the Award P5S-VM Rev 1006 BIOS from Asus works flawlessly on their machine and already increases performance by 5-10% with the original CPU installed!
And with my patched version of this BIOS, one HP 6640C user is running a K6-III+/500 overclocked to 600MHz on 2.1V Vcore without any problems.
But there is a snag!
Because the Asus OEM P5S-VM board in the HP Pavillion 6640C has a Phoenix BIOS now, you will be unable to flash an Asus BIOS. It seems the
Phoenix BIOS has some unknown locking mechanism on the flash chip that doesn't allow to flash any other BIOS then a Phoenix BIOS.
Several flash programs, including Uniflash, were tried to no avail.
So you will need to use an (E)EPROM programmer, or order another flash chip (the Winbond W29C020 is a good replacement) with the P5S-VM Award BIOS in it.
This can be either the original Asus BIOS or my patched 1006vmj1 version.
A good place is
http://www.badflash.com. Badflash knowns my BIOS and can send you a replacement flash chip with the 1006vmj1 BIOS already programmed in it.
You can download the patched 1006vmj1 BIOS from my k6plus page. The link is in my signature below.
Good luck with the upgrade!
Jan.