Hello Hitman,
We don't have any release notes for that particular BIOS at this stage, but I think I can shed some light on the difference between the 2.00 and 2.06 BIOS for the VXIpc-870 (original series). The BIOS was primarily updated in order to support faster processor speeds of the Pentium III CPU. This has to be done on occassions when Intel releases new CPU ID's for new processors if we are planning on upping the controller's speed (case in point, the VXIpc-870 was bumped from a speed of 450Mhz up to 700Mhz later in its life). I do not think the new values were ever actually used, but were put there just in case.
There were also changes made to the BIOS to support more types of flash chips on which the BIOS resides. The BIOS has to be aware of the type of media on which it is contained for the purposes of write protecting itself. I did not find any information on bug fixes or otherwise, so I imagine you will see very little performance difference between the two versions.
In short, basically just a minor maintenance release. Hope this helps.
Joshua Hernstrom
PXI/VXI Software
National Instruments