There are about five "classic" Viper cards. Each uses different chipsets and has different BIOS versions. The following table tries to summarise the important information.
|Model||Interface||VGA Chipset||VGA RAM||SVGA Chipset||SVGA RAM||RAMDAC||BIOS|
|Viper VLB||VLB||Oak OTI-087||256K DRAM||Weitek P9000||1M/2M VRAM||Bt485 135Mhz||1.x, 2.x, 3.x|
|Viper PCI||PCI||Oak OTI-087||256K DRAM||Weitek P9001||1M/2M VRAM||Bt485 135Mhz||V3.10 (1993)|
|Viper SE||VLB||Weitek 5186||1M DRAM ??||Weitek P9100||2M/4M VRAM||Bt485 or IBM525 170mhz||1.04, 1.05|
|Viper SE||PCI ??||Weitek 5186||1M DRAM ??||Weitek P9100||??/2M VRAM||IBM525 170mhz??||??|
|Viper Pro Video||PCI||Weitek 5186||1M DRAM ??||Weitek P9100||??/2M VRAM||IBM525 170mhz||??|
(If you have any information or corrections to add to this table please mail the author)
About the Oak OTI-087 (S)VGA Chipset
One of the first VLB chipsets available, it has a 16-bit external data path, and a 32-bit internal memory-controller data path, it also has register-based color expansion, hardware cursor, a primitive BitBlt engine, a 64 bit graphic latch and some other new (on its time) features. Maximum BIOS resolutions are 1024x768x256 Non-Interlaced and 1280x1024x256 interlaced. Maximum Dot-Clock is 80Mhz, but is usually coupled with the OTI068 clock generator whose highest frequency is 78Mhz. Supports up to 2MBytes of 70/70R ns DRAM. (Original source)
Note however, it was present on the P9000 Vipers with only 256K DRAM and functioned purely as a standard VGA adapter, and a very slow one at that!
The P9000 models use a Brooktree RAMDAC (Model Bt485). Most run at 135Mhz, but there is known to be some models which only have 110Mhz badged on them.
The Viper VLB and Viper PCI are identical in functionality expcept for the different bus interface and the slight alteration of the P9000 to P9001 to allow it to work with PCI.
The Viper actually has a VESA driver built into its onboard BIOS, but as you know, you have to still run VPRMODE VESA to use VESA. Why? Because Diamond could not engineer it to automatically enable it like all other cards -- the VPRMODE VESA command does this with software!