• Please review our updated Terms and Rules here

Question about 286 motherboard

vladstamate

Experienced Member
Joined
Dec 2, 2012
Messages
197
Location
Orlando, FL, USA
Hi all,

I've obtained this IBM PC which had the top cover of the 5150 but the power supply on the back says 5160. When I opened it, it seems to be a 5170 actually as it has a 286 CPU !! Imagine my surprise. Now it powers on but all I get is double beeps. It had a MGP (?) graphics card (I CGA or MGA I think) so I removed that as when I connected my CGA to it, it did not want to display anything. Anyway, so I put in a 16 bit ISA VGA card. Same result, double beeps and no display.

I took a picture of the corner of the board. Does it look like I am missing memory (due to empty slots) or are the chips just below that memory?

IMG_0113.jpg

The reason I am asking is because the memory is missing then it explains why the PC is not starting, but also because the chips below the empty slots do look like memory chips (they have the -80 at the end indicating 80ns chips).

Regards,
Vlad.
 
I think the RAM is already installed; the 12 chips adjacent to those empty spaces include a couple of 256kbit RAM chips. I can't read the labels of some of the others. I believe the empty spaces are SIPP slots. If you want to, it should be possible to install 30 pin SIMM sockets and add more RAM. Probably either 256kB or 1 MB SIMMs.

Which BIOS manufacture is listed? That would suggest what error code is being indicated. My expectations are variously bad CMOS (including dead battery) or the video switch is set incorrectly though bad memory or some other component having failed is possible.
 
Thank you.

I will try installing a known working CGA card (which I have in a 5160). The motherboard BIOS is in the picture below (looks like Quadtel).

IMG_0111.jpg

One of the first thing I looked for was switches. I cannot see any (definitely nothing like I would expect from a proper 5170 286 motherboard, which I assume this is not). There are some jumpers but without the manual it is hard to know what to make of them. Also I assume since this is a 286 motherboard it will take a AT style keyboard right? Not a original IBM PC keyboard? The connection is almost the same (5 pins).

EDIT: rotated the image.

Regards,
Vlad.
 

Attachments

  • IMG_0111[1].jpg
    IMG_0111[1].jpg
    87.3 KB · Views: 1
Well, a listing for Quadtel is at http://www.5starsupport.com/info/beep_codes.htm and suggest CMOS problem. 99% of the time, replacing the battery is all that is needed. Other 1%, the CMOS itself went bad which is harder to replace.

Most 286 equipped motherboards used an AT keyboard. There were a few oddballs that used XT keyboards but I think those stopped being made by the time SIPP and SIMM became available. Try AT mode first, switch to XT mode, and if both fail, check if the keyboard connector got pulled loose from the motherboard.
 
Wasn't unusual for clone mobos to be fitted to IBM chassis. There should be markings on the mobo to identify it. This helps a help of a lot with regards to memory set up, external battery headers and what not. Yes, should take an AT keyboard fine.
 
Last edited:
It's a 286 but not a 5170.

There are probably one or more bad memory chips and that's keeping the machine from booting. You'll need to verify the integrity of the memory chips to get anywhere with this.
 
That Quadtel package is the keyboard bios. The actual mobo bios is a Chips and Tech. 286 Bios set. Hey, you my even be lucky enough to have the C&T NEAT chipset on that mobo.
 
Last edited:
I think the RAM is already installed; the 12 chips adjacent to those empty spaces include a couple of 256kbit RAM chips. I can't read the labels of some of the others. I believe the empty spaces are SIPP slots. If you want to, it should be possible to install 30 pin SIMM sockets and add more RAM. Probably either 256kB or 1 MB SIMMs.
It depends. On some motherboards, the SIPP and DIP sockets are at the same addresses; i.e. the motherboard maker gave the owner a choice of using either SIPP or DIP.
 
It depends. On some motherboards, the SIPP and DIP sockets are at the same addresses; i.e. the motherboard maker gave the owner a choice of using either SIPP or DIP.
My original 286 was like that. It was either/or but not both. This board may even be lucky enough to be able take up to 16megs. Without more detail about the board itself, ie it being correctly identified, it just pure guess work.
 
With no identification of the motherboard yet, what you could do is temporarily assume that the 2 beeps indicate a failure in the lowest block of RAM (considered critical to operation). Have you tried reseating the RAM chips in case of a poor connection? Have you tried swapping the chips about the sockets - something that may relocate a bad chip out of the lowest block of RAM ?

Also, do you have a suitable POST card? The code displayed by that, and reference to the lower table at [here], would probably point you in the right direction.
 
Also, the picture only shows the even BIOS chip. It's possible that the odd chip is missing as there's half an empty socket visible.
 
Also, the picture only shows the even BIOS chip. It's possible that the odd chip is missing as there's half an empty socket visible.
The "EVEN" on that BIOS chip does strongly suggest that there should be a matching ODD chip somewhere. I used "suggest" because there exists the possibility of mislabeling. But, if there is meant to be an ODD chip, and it is missing, then I would find it hard to believe that the motherboard could produce 2 beeps if every alternate byte of BIOS code is missing. One long continous beep, yes, but not 2 distinct beeps.

However, I do agree that it is possible (just very highly unlikely). No, I am not prepared to put money down.
 
So I left the computer running for a bit, about 40 minutes. Powered off then on again and this time no more 2 beeps. This seems to indicate the battery did get enough charge. Instead now I am getting a longish beep + 2 short beeps. I looked for a C&T beep table but could not find one. Does anyone know of where can find codes?

The computer DOES try to boot however sometimes. I see the light and the engine of the floppy driver working and the HDD as well.

Also, I have ordered a POST card.

Regards,
Vlad.
 
Also, there is no "ODD" BIOS chip that I can see on the motherboard. There is no empty socket either, so I assume a mislabel? Also the POST goes pretty far for half the BIOS not to be there (like INT 13 is there it seems).

Regards,
Vlad.
 
It looked like there was an empty socket behind the Quadrel chip. I just used The Gimp to enlarge the image, then adjusted the contrast and brightness to have a better look.

.
 
Last edited:
So I left the computer running for a bit, about 40 minutes. Powered off then on again and this time no more 2 beeps. This seems to indicate the battery did get enough charge. Instead now I am getting a longish beep + 2 short beeps. I looked for a C&T beep table but could not find one. Does anyone know of where can find codes?

The computer DOES try to boot however sometimes. I see the light and the engine of the floppy driver working and the HDD as well.

Also, I have ordered a POST card.

Regards,
Vlad.
Looking at some older bois beep codes, 1 long 2 short seems to indicate a video related issue.
 
IBM had long beep followed by 2 short beeps as video card issue. Many clone BIOSes followed IBM's lead.

You may need to do a full set of pictures of the motherboard. It is possible that a chip got mislabeled or someone swapped chips into the wrong sockets. A more complete view of the board might just provide the hint as to the exact model from which details can be derived.

http://stason.org/TULARC/pc/motherboards/m286_1.html shows a lot of 286 motherboards. Several other pages there show additional motherboards. Finding a SIMM based variant (with possibly a different BIOS) could help locate any jumper that might need to be reset. I see a few with 12 DIP sockets and 4 SIMM slots and C&T chipset which is close to what you have so maybe you can narrow things further. Not installing the SIMM sockets and leaving just empty SIPP holes in the motherboard saved the manufacturer a few dollars.
 
Back
Top