VESA VL-Bus standard - Page 1
Forum section: electronics / general

author: HwAoRrDk
author_rank: Super Contributor
timestamp: June 22, 2021, 03:30:46 pm
content: This is probably a shot in the dark, but who knows...Does anyone know of anywhere that acompletecopy of the VESA VL-Bus Standard specification document can be obtained? Specifically, I'm looking for the dimensions/drawing of the card edge connector and slot.I already foundthis thread on VOGONS, where the poster there asked VESA for a copy of the spec document, and which was provided, except that PDF file has one fatal flaw... it doesn't include the card physical layout drawings! On the pages where they're supposed to be are just blank areas with the note "Diagram Cut & Pasted at this time" (whatever that's supposed to mean).I searched a few other places but came back empty-handed - bitsavers.org, Google Patents (was thinking maybe some entity included a copy in a patent), PUDN.Maybe there's a scan of an original paper copy out there...Alternatively, does anyone know of any part number, etc. for motherboard slot connectors? Maybe drawings/datasheets for those will have enough info to infer the card edge connector dimensions. I have an old 486 board here that has Molex slots on it, but I couldn't find anything from a brief search. Were the slot connectors some form of off-the-shelf generic connector that perhaps went under another name?

author: HwAoRrDk
author_rank: Super Contributor
timestamp: June 22, 2021, 06:50:32 pm
content: Aha! Going down the avenue of looking for specifications of VLB card slot connectors has paid off!As mentioned earlier, looking for the particular Molex slot on the old motherboard I have access to didn't yield anything, but what about other manufacturers? Just on a whim, I went to Digi-Key, intending to look in general for other 112-pin card edge connectors. Well blow me down, they actually have a parametric filter entry for "VLB"! Filtering on that returned just one result: TE/AMP part no. 5650090-1.Loading up the drawing PDF revealed, as I hoped, that TE have included the layout and dimensions of the mating edge connector.I was able to verify against the one single dimension that is mentioned in the VESA standard document: total length of the card edge tab, which is 2.92". Total length of the 'S' and 'U' dimensions in the TE drawing: 2.92".

author: Rasz
author_rank: Super Contributor
timestamp: June 24, 2021, 01:03:16 am
content: Didnt VLB just reuse MCA connector? later again reused as PCI?

author: HwAoRrDk
author_rank: Super Contributor
timestamp: June 24, 2021, 03:20:48 am
content: Yes, I learned it is the same as MCA.In fact Digi-Key also sell an MCA slot connector from Sullins that is identical.PCI is not the same, it has more pins (124 vs 112).

author: madao
author_rank: Frequent Contributor
timestamp: July 20, 2021, 01:38:09 pm
content: I have developed some VLB graphic card based S3 Trio64v+/S3 Virge and S3 Vision968 with 4MB memory. (same nick by vogons)I can tell 13mm distance between pin from ISA and VLB. (middle of VLB-pin to middle of ISA pin )But , i am not sure 12,7 or 13mmTwo photo show my developed VLB graphic card.Next goal is huge ISA card and finished of Virge VLB projekt.Yes, VLB Slot is just a MCA slot, which it is 180° turned.I have some motherboard with "MCA" Marking on VLB

author: HwAoRrDk
author_rank: Super Contributor
timestamp: July 20, 2021, 05:27:10 pm
content: Quote from: madao on July 20, 2021, 01:38:09 pmAwesome!Quote from: madao on July 20, 2021, 01:38:09 pmDefinitely 12.7mm. The VESA standard document specifies 0.5 inches pin-to-pin distance between ISA and VLB.

author: madao
author_rank: Frequent Contributor
timestamp: July 21, 2021, 02:52:41 pm
content: ThanksI have only 3 VLB motherboard at this time, which most motherboard have 13mm distance between pin. This is why i am not sure.

author: HwAoRrDk
author_rank: Super Contributor
timestamp: July 21, 2021, 05:41:03 pm
content: I would not put too much faith in every motherboard always having correct dimensions.For example, the 486 board I have here (QDI PX486P3) actually has incorrectly designed 16-bit ISA slots, where the divider between the front and rear sets of pins is too small. When you insert a card, all the rear pins are offset by about 0.5mm!The distance is supposed to be 0.4" / 10.16mm, but this one measures less. The slot connectors are branded 'Nextron'. Pins still make good enough contact, so it still works - you would only notice if you look closely.