How to convert a Multia SCSI/riser card into a 'normal' NCR810 adapter

©1999 Wilko Bulte - - Mon May 31 20:03:47 CEST 1999

The issue has been brought up if a Multia SCSI/riser card (DEC part# 54-22563) can be converted to an ordinary NCR810 adapter, suitable for use in a standard PCI slot. After some research the question can be answered affirmative.

The conversion procedure involves cutting 5 etch traces and adding 4 wires.

This is Dragon country, you need some expertise in handling a soldering iron and fine-line etches. I also suggest doing it right the first time. My suspicion is that PCI bus chipsets might be easily damaged. If you kill things, tough luck and I feel sorry for you, but you do this on your own risk.

In addition I suggest you test the converted board in some old PC first. Especially if you have a LCA 21066 based Alpha box. Those have their PCI stuff more or less directly connected to the Alpha chip. Don't say I did not warn you..

If you don't feel comfortable with the procedure then don't perform it!

I've converted 2 boards now, and both work fine in i386 and Alpha boxes, using NetBSD/alpha, FreeBSD/alpha and FreeBSD/i386.

The actual procedure

General info

Note that there are multiple incarnations of the riser card. The actual PCB is the same, but they are populated with different parts (mainly connectors).

The ones I used did not have a PCI expansion connector and had a SCSI cable directly soldered to the board. It should not make much of a difference which variation you use, other than that you might have to add or remove other components aside from the etch cuts/wires I describe below.

Side 1 of the circuit board

This is the 53C810 (NCR810) side of the board.
(click on the picture for a higher-res one)

Side 2 of the circuit board

This is the crystal oscillator side of the board.
(click on the picture for a higher-res one)

The crystal oscillator is the little black box with 40.0000M stamped on it.

You will now have to add/remove whatever components you (don't) need. Things like connectors etc. Should be a pretty obvious operation.


Again: I strongly recommend testing the converted board in a PC test machine. Meaning: don't try this in your most valuable quad Xeon SMP box or Turbolaser. I myself tend to use an older P100 Abit mainboard for this kind of stuff.

My two converted cards worked fine the first time. So I can't tell you what the effects are if you botch it..

Using it

The size and layout of the board make it impossible to fit a normal metal PCI bracket to it. In my experience the lack of a mechanical fixture does not really matter to much. If you think otherwise you need to get creative.

Comments/constructive critiscism

Send your comments & suggestions to Flames etc to /dev/null.

Request: if somebody with a digital camera could send me a couple of sharp pictures of an unmodified board I will add those to this Web page to clarify things a bit more.