• Please review our updated Terms and Rules here

IBM 5150, 8087 and POST 131

R

rimmer

Member
Joined
Apr 1, 2011
Messages
12
Hi everyone.

After installing an Intel 8087 in my IBM 5150, and setting the jumpers to reflect this upgrade, my computer constantly posts with a 131 POST error, before continuing like nothing was afoot.

Has anyone had similar issues? I'll try and open the 5150 up tonight, and post specs on my 8087. Perhaps it's a too fast processor for my machine?

Please note, that no software test have been done on the 8087, except the "8087.exe"-utility from my IBM Pascal 2.0 disks. This utility detects the processor, and is seemingly able to dis- and re-enable it.

Any thoughts on this issue are most welcome!

Cheers,
Anders

--- edit ---
Seems I must have inadvertently knocked one of the PSU cables loose, when installing the 8087... Once properly reseated, everything works like before...(!)
Well, apologies all around to those of you, who's spent time working on a solution to this man-made error of mine. One good thing came of it, though; I got to purchase new tools!

Cheers, and thanks again!
--- eidt end ---
 
Last edited:
http://www.bioscentral.com/misc/ibmdiag.htm said:
131 Cassette wrap test; DMA compatibility registers error
Click to expand...

This indicates that the relay on the board in charge of casette data loopback may have some issues. What is the setting of the jumpers on the board?
 
OK, I guess I have to clarify my post.

1: The computer booted fine pre-insertion of the Intel 8087
2: The computer, post installation, pre re-switching (SW1.2 set to ON (8087 not installed), displayed 131
3: The computer still posts 131, after I set the SW1.2 to OFF (8087 installed)

The computer has the following conf:

SW1: 0 0 0 0 1 1 1 1
SW2: 1 0 1 1 0 0 0 0

It has one floppy, hard card 20, 256 kb on-board, 384 on two cards, AST MDA/CGA/EGA card, IBM floppy controller

The Intel 8088 CPU states:
IBM 4481480
14 14 PQ
D37A01EA
(c) Intel '78 '81

The Intel 8087 FPU states: (I guess this is an original 10MHz part?!)
D8087
L9500422
(c) Intel '80

So, could the FPU be "to fast" for my 5150? Or am I missing something? I got the FPU last week, NOS from the Ukraine. Still in the Intel rail-thing.

I *did* read the POST list, and since I:
1: did not change anything other than installing the FPU prior to the POST 131 and
2: doesn't trust IBM to *only* POST the correct numbers.
I just don't think the Cassette path is the way to go. But I'm to dumb to figure out for myself, of the "DMA Registers" can pertain to my "new" FPU.

Like I said, I might be wrong. Dunno. Also, I know I should test the FPU, but I only have a 1.2meg 4869-502 for the PS/2, and am therefor unable to transfer software from the internet to the 5150, such as "PC Diagnostics" and others. Any one out the with the 360kb 4869-501, I'm in the market!

Cheers, and many thanks for the input.

/Anders
 
Does it work ok if you remove the chip again? (Confirms at least that's the only problem)
 
There is also a jumper block which controlls the casette output. What is this/these jumper/s set to?
 
I'm unable to remove the chip again - I don't have the proper extraction-tool, nor the guts to potentially break chip, board or both, while trying to pry out the chip with a flat-head screwdriver.
 
TNC said:
Such a thing is an investment for life! :)

http://cgi.ebay.de/ws/eBayISAPI.dll?ViewItem&item=220755841873
Click to expand...

Uh, the 8087 is a 40-pin DIP, not a PLCC. This is what you want for 0.600" DIPs:

122X081_PLI.jpg


Forget the eBay no-name junk--the OK tool is only about $20.

You may want to remove the 8087 anyway--bent pins can be very difficult to see when the chip's in a socket. If you're worried about bent pins, get a 40-pin machine-pin DIP socket and insert the 8087 into it, then insert and extract the 8087+socket "stack" into the motherboard socket.
 
Fantastic! Ordered one from Digikey!

Although, I'm 100% sure no pins are bent. I'm somewhat skilled in soldering and assembly of PCB's and IC components, and I know to be careful. All the same, I'm very grateful for all the advice I get from you fellow enthusiasts. And one can never get to many tools!! Anyone with recommendations for an extraction tool for x64 ram chips? I'm looking to consolidate my two RAM expansion boards, thus freeing up a slot for another use.

As to my original question; no one here on the board has ever experienced a "rouge" POST 131?

I'll check the cassette jumper/switch now, and post my findings. But I *know* I re-configured nothing in this regard, and I *know* the POST wasn't there before!
 
I recall reading on here before that the DIP switches may look switched but actually aren't quite home. Just a thought.
 
Maybe the relay on the 5150's motherboard got stuck. It's the rectangular component with the translucent cover near the cassette port. Try tapping it gently with the back of a screw driver.
 
rimmer said:
The Intel 8087 FPU states: (I guess this is an original 10MHz part?!)
D8087
L9500422
(c) Intel '80

So, could the FPU be "to fast" for my 5150? Or am I missing something? I got the FPU last week, NOS from the Ukraine. Still in the Intel rail-thing.
/Anders
Click to expand...

It seems that you have a 5 MHz version (D8087), 10 MHz versions have "-1" suffix, like: D8087-1

There is no "too fast" FPUs, faster FPU will work with slower CPUs.
 
You must log in or register to reply here.
Back
Top