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VLB Riser With ISA/PCI Swaps

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First post, by rarcher

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Good evening everyone! Sorry about the likely odd thread title, but I was not quite sure how to word this exactly.

So I am still working on outfitting my IBM Valuepoint 486DX2/66 6482 model. As I mentioned in my mid-life crisis thread I ran into some road blocks/set backs with some stuff. But while working to fix those issues, I happened to be looking at the IBM manuals for this that list parts/options for the different models.

The attachment 6482-6484-PC-Options.png is no longer available
The attachment 6482-6484-PC-Options-2.png is no longer available

As you can see here mine is one of the 6th to the 4th options from the bottom, the 6482's. These have a VLB slot which then uses a riser card to add ISA and a VLB port on it. But the 6484's, the last three near the bottom there have a VLB slot which uses a riser card that gives 2 ISAs and 2 PCIs (maybe a single VLB too? Not sure). So I got to wondering as the second picture above shows the ISA/PCI riser option was an add on for 115 bucks back then. So I'm curious if anyone could tell me if I was somehow able to find this card do you think it would work in my 6482? Or is it likely only something the 6484s got? I only wonder on this, because if I could get PCI on this PC it would solve alot of my headaches I'm having with price and such in getting say better soundcard or ethernet card, maybe even a PCI based graphics card.

I've also included the ISA/PCI raiser part number from the booklet but googling this part number doesnt turn up anything sadly.

Basically my intention is to possibly get either a good workhorse gaming oriented graphics card (ISA/VLB or if this idea works PCI), same for a soundcard and ethernet card.

I'll be diving into reading up on the forums here about isa/vlb card options but from a glance so far when then looking to options given I'd be paying too much for what I want. So I'm figuring given I don't plan to do much gaming for now focus on the ethernet and sound card options (again i'm not audio nut guy so having a good 'all around workhorse' sound card would be ideal) seems though in both cases PCI options seem more viable in price then ISA/VLBs

Can anyone enlighten me on this? Or perhaps provide a better suggestion in some form?

Thanks again!

Last edited by rarcher on 2022-08-09, 18:51. Edited 1 time in total.

Reply 1 of 7, by majestyk

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There were riser cards that had their own VLB to PCI bridge-chip. These are quite hard to find today.

Reply 2 of 7, by douglar

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majestyk wrote on 2022-08-08, 05:32:

There were riser cards that had their own VLB to PCI bridge-chip. These are quite hard to find today.

Where they tied to a particular chipset & BIOS or were there any risers designed with the idea of working any standard VLB motherboard?

Like could you use one to add PCI to a 386 VLB motherboard?

Reply 3 of 7, by majestyk

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The ones I´ve seen had something like the VIA VT82C505. This document describes the inplementation:
https://dosdays.co.uk/media/via/VIA_82C505.pdf
They are talking about 486 platforms there.

Last edited by majestyk on 2024-05-30, 06:01. Edited 1 time in total.

Reply 4 of 7, by douglar

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Makes sense. I got a FIC VIP motherboard with that chip . The VLB works fine but the PCI performance isn’t what you could hope for.

If there was a riser card, seems like you could put it on a board like this to get 386 PCI:
https://theretroweb.com/motherboards/s/dataex … x-3-486wb-cache

But it seems likely that you would run into some show stopping instructions in a driver that would make compatibility difficult. But if you didn’t, you could get some bragging rights if you had a 386 with PCI slots.

Reply 5 of 7, by kingcake

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douglar wrote on 2024-05-27, 13:29:
majestyk wrote on 2022-08-08, 05:32:

There were riser cards that had their own VLB to PCI bridge-chip. These are quite hard to find today.

Where they tied to a particular chipset & BIOS or were there any risers designed with the idea of working any standard VLB motherboard?

Like could you use one to add PCI to a 386 VLB motherboard?

I'm fairly certain you'd need BIOS support and/or an option rom to patch the BIOS on boot.

Reply 6 of 7, by majestyk

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Mainboards with bridge-chips like the VT82C505 are generally viewed as "inferior" compared to mainboards with PCI chipsets.

I´d like to know why. If we say the VLB bus is basically the CPU bus, a mainboard with a "true PCI-chipset" must have a CPU-bus / PCI-bus bridge inside one of it´s chips, while a mainboard with the 505 PCI-controller bridges VLB / PCI with a dedicated chip. I wouldn´t expect a big difference here, so what´s the reason behind it?

Reply 7 of 7, by douglar

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majestyk wrote on 2024-05-30, 05:52:

Mainboards with bridge-chips like the VT82C505 are generally viewed as "inferior" compared to mainboards with PCI chipsets.

I´d like to know why. If we say the VLB bus is basically the CPU bus, a mainboard with a "true PCI-chipset" must have a CPU-bus / PCI-bus bridge inside one of it´s chips, while a mainboard with the 505 PCI-controller bridges VLB / PCI with a dedicated chip. I wouldn´t expect a big difference here, so what´s the reason behind it?

That's a good question. Seems like it shouldn't have to have a performance hit, yet it does.

Could it be that it was a first gen 3rd party PCI implementation married to a design that had extra wait states added to give motherboard designers electrical wiggle room?

Probably was never updated because the VT82C505 was good enough for marketing purposes and the cost of "second chip" implementations wasn't competitive after the next gen single chip implementations arrived.

But that's just a guess.

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