View Full Version : IBM PC AT 286 BIOS Error 106

April 11th, 2010, 09:43 AM
Hey, guys..

A few days ago I responded to a Craigslist post for an IBM XT 286 for $100. As I get him to send me pictures, it turns out it's actually an IBM AT 286. No biggie. Problem is that when he boots it up, it's giving him a BIOS error 106 and won't boot. From what I've found, 106 errors is a system board error, failing the converting logic test. I can't seem to find any detailed information about this error.

Is anyone familiar with this error? I haven't purchased the system yet. What I'm looking to find out is whether or not it's still worth purchasing the machine with this error, if this error is repairable without a motherboard replacement, and ideas on what this machine is worth with the error as-is.

Also, note that the owner seems to think that this error is related to a bad battery - and while I'm sure that the battery is bad after all this time, that's not the error that the BIOS is giving us.

Thanks for any input you guys can provide.

April 11th, 2010, 10:11 AM
If nobody knows right off, I canl look at the BIOS source code and see what gives.

April 11th, 2010, 11:10 AM
106 System board converting logic test failure ?


That is PS/2 though..

April 11th, 2010, 12:32 PM
I saw that as well, Jorg - thanks! I'm looking to see if anyone has any idea of what the likely culprits for such an error are. My ultimate goal is to be able to (easily) repair this thing and make it mine. If this guy can't get his hard drive connected and delete the data he's worried about, I don't think he'll be willing to sell it to me at all. With that said, he's asking $100 for the unit, with IBM Hercules monitor and keyboard (non-IBM, he thought, and the pics were indeterminate), as well as 4-5 diskettes. No system manuals, no IBM books, no original boxes. Working, it's worth $100. Non-working? I've no idea. I know that it's possible that just giving the board a good cleaning, reseating socketed chips, etc could "fix" it. I guess I'm looking for other possibilities.

April 11th, 2010, 03:09 PM
212xx A fault has occurred with the SCSI printer - replace the SCSI printer

didn't know a scsi printer was ever produced

April 11th, 2010, 06:03 PM
Okay, since no one else has checked it out. Error 106 "Converting logic" is the usual IBM gobbledygook for "DMA page register". In the IBM PC AT Techref, you'll find the code that generates the stupid message about halfway down page 5-52. The message in question has tag CM_4A. Basically the test outputs a word to I/O port 82H, then inputs bytes from 82H and 83H and checks them against what it output. No match means error 106.

Practically speaking, this means that you should check U124, a 74LS612, a big 40-pin DIP--a TI "Memory mapper". Often, these are in sockets and so removing it from the socket, checking it for bent pins, then re-seating it in the socket will often cure the problem. Replacing is easy, if you can find them. Unicorn Electronics has them and I'd suspect that some of the sellers on the marketplace might also. Ebay might have one--I haven't checked.

April 11th, 2010, 06:04 PM

The guy writes me back this evening. "oops, I typoed. It's error code 160. Sorry. I soldered a camera battery to the old wires and it works now."

So I look up code 160 and find it's " PS/2 system board ID not recognized" - for an AT? Huh?

I really need to find PDFs of the old Hardware Reference Manuals...

Speaking of manuals, what version of Mueller's Upgrading and Repairing PCs do you guys use for XT/AT repair and lookup? I have the 11th edition, from 1999. I've never seen another edition. It seems to be focusing on the PCI/P3 era, as it should..

April 11th, 2010, 07:51 PM
'There's no 160 error for the PC/AT. There is an error 161 that indicates a dead battery.

Is this guy dyslexic?

I use the IBM techrefs for everything. If, with the schematic and BIOS listing in front of me, I can't figure out what's wrong, it's time to hang up my soldering iron and take up macrame.

If you ever run across a full set of the "Options and Adapters", I recommend that you fall on it.)

April 12th, 2010, 04:18 AM
If you ever run across a full set of the "Options and Adapters", I recommend that you fall on it.
On my list-of-things-to-do is the item, 'Scan Options & Adapters books'.