The latest published BIOS file (by PCChips) is dated 04/30/98 and is the one I am currently using on my system.
It seems stable, and allows the use of CPUs with clock speeds in excess of the standard 233Mhz. Inparticular it correctly reports the AMD K6 and K6-2 CPUs.
It does not configure the latest K6-2 CXT core chips correctly, in order to enable write caching a separate program is required such as SETK6.
Although a fellow VX-PRO+ user thought he had tracked down an update, it proved to be for an M80 motherboard sold by ACER.
If you feel like 'tinkering' further with your BIOS setting, there is a program called "MODBIN" which used to be available on the Award site to look at 'hidden' setting of the Bios, I've not tried this program and am passing on this information in good faith at this time.