[rescue] Vesa Local Bus video cards

[Francisco Javier Mesa-Martinez]

On Mon, 31 Mar 2003, Phil Stracchino wrote:

> Problem was, VLB was very limited in capacity.  You could have three VLB
> slots on a 25MHz bus, but the spec only allowed two on a 33MHz bus and
> one at 40MHz.  At bus speeds over 40MHz, you couldn't use VLB at all.

The VLB was pretty much the 486 bus, you could run it at 50MHz w/o any
slots due to the unbuffered nature of the 486 bus.


> The future of local bus also wasn't helped, of course, by the period
> during which it seemed every manufacturer had their own proprietary
> local bus, and none of them were compatible or interoperable.

I do not remember seeing that many different local buses, there may have
been different physical connector approaches. Since all those local buses
were pretty much a "tap" on the 486 bus :). Almost like the PDS slots in
some 68K macs.

 That
> kinda made local-bus a dirty word among people who wanted to be able to
> get the most out of their machines.  At the time, EISA was a technically
> better solution, certainly a more completely thought out solution, and
> the PC-based server market went with EISA, which pretty much nailed the
> coffin lid down on local bus.  OK, so it might be a slightly slower bus,
> but you could have as many 32-bit slots as you could afford.

I think EISA came before VLB, VLB was never inteded to replace EISA, in
fact I have seen EISA/VLB motherboards. It was just a way of having a fast
pipe to graphics boards, since both EISA and ISA could choke with some of
the datarates needed for full resolution 24bit imaginery. Think of the VLB
as the yesteryear's AGP. I think the only other boards that I have seen
employin the VLB standard were SCSI adapters....