VOGONS

VL-Bus Specifications

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First post, by gloomkeep

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First post! Not sure if this is the right place to post this or if anyone in the world other than me cares, but ...

I got back into 486 machines recently and have been trying to learn more about their architecture.

I haven't had much trouble finding information about the ISA bus (both at the electrical and functional levels), but I couldn't find much about the VESA Local Bus other than pinouts and minor discussions.

Perhaps to have access to the specifications you had to be part of an organisation with VESA membership back in the 90s?

So I got in touch with the VESA organisation and they agreed to release the VL-Bus specifications publicly / for free! It is not yet on their website, but I've attached:

VLBUS20.PDF

VESA VL-Bus Standard Version 2.0 (Dated: November 1, 1993)

PLUGPLAY.PDF

VESA VL-Bus Plug and Play Addendum (Dated: April 11, 1994)

Enjoy!

Reply 1 of 9, by The Serpent Rider

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Well, time to start building those 486 VLB boards.

I must be some kind of standard: the anonymous gangbanger of the 21st century.

Reply 2 of 9, by firage

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Nice! Good work, man. Very cool from VESA, most of all.

My big-red-switch 486

Reply 4 of 9, by Anonymous Coward

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Note that this is VL-bus specification 2.0. From what I remember, almost all motherboards and cards use specification 1.0.

"Will the highways on the internets become more few?" -Gee Dubya
V'Ger XT|Upgraded AT|Ultimate 386|Super VL/EISA 486|SMP VL/EISA Pentium

Reply 6 of 9, by root42

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Wow, this is amazing. Wonder what people will come up with...

YouTube and Bonus
80486DX@33 MHz, 16 MiB RAM, Tseng ET4000 1 MiB, SnarkBarker & GUSar Lite, PC MIDI Card+X2+SC55+MT32, OSSC

Reply 7 of 9, by gloomkeep

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Anonymous Coward wrote:

From what I remember, almost all motherboards and cards use specification 1.0.

I asked for the v1.0 spec a couple of weeks ago, but they don't have a copy anymore.

They've explained most of the (small) differences in the v2.0 spec, and on p28 you can, in a way, determine through ID bits what version is likely supported by a motherboard.

(i.e. it seems like it's up to the card to decide whether to fall back to v1.0 support or not)

spec_v2.0.png
Tiido wrote:

The differences are very minor and only have to do with writeback cache and burst cycles it seems.

Yep, and 50MHz spec and 64-bit data bus.

Reply 8 of 9, by Jo22

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Thank you very much for your efforts, sir! 😀

"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

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Reply 9 of 9, by debs3759

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Very nice, thank you. Have added them to my library.

See my graphics card database at www.gpuzoo.com
Constantly being worked on. Feel free to message me with any corrections or details of cards you would like me to research and add.

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