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IBM 5150 memory repair

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musicforlife

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I have got two 5150 computers with similar ram issues. Both are fitted with full 64kb for all 4 banks but first one gets ram error until you change switch to "only bank 0 fitted" so I simply need to change the ram for new? However the second computer gives me ram error even when it's only bank 0 selected. How can I change the directly soldered ram? Do I need to replace them with actual sockets or do they withstand direct soldering by hand?
 
First, I'd suggest testing both boards with the socketed RAM removed. Then add it back one bank at a time, swapping around chips. It sounds like that first one might be OK. You want to be sure the RAM on the second one is actually the first bank, and not something else interfering with it.

Are these 16-64k or 64-256k boards?

Exactly what RAM error code does the BIOS return?

The first step is to make sure the soldered RAM is bad or not, and which chip is at fault.

If it is bad, then the only thing you can do is unsolder it and install a socket. For consistency and to make future RAM errors easier to deal with, you may wish to socket the entire bank at the same time.

If you are having problems testing the RAM or the motherboards, you might want to try using the Supersoft diagnostics: http://minuszerodegrees.net/supersoft_landmark/Supersoft Landmark ROM.htm
 
I second that recommendation. I had a dead 5150 that I brought back to life by using the Supersoft diagnostic ROM which indicated a problem with the Bit-7 chip in bank 0. I socketed & replaced that chip and the system came back to life no problem. eBay was a great source for replacement 4116 IC's.

De-soldering was a bit of a pain, but I got the hang of it after 15 out of 16 pins... The IC that was in there was so fragile that a gentle pull/pry broke it.

Good luck!
 
Be aware that we have had 5150 owners reporting a 201 error, and it turned out that there was nothing wrong with the RAM; the problem cause was the motherboard switch settings. So, an early thing to do is verify that the correct settings are being used for the scenario, noting:

1. The RAM configuration switches are in both SW1 and SW2.

2. The SW2 settings vary according to the BIOS revision fitted to the motherboard (as per the 'Switch block SW2' section at [here]).

3. Bugs in the 10/27/82 dated BIOS revision require that all four RAM banks be populated, and switches set accordingly. End of story. With the 10/27/82 BIOS fitted, trying to do bank isolation diagnosis by adjusting SW1/SW2 can result in invalid/misleading results.
 
The models are 16-64kb. Also I am sure about the switch settings. Before I started taking the chips off, the bank 0 was working again out of blue while I didn't change any settings.

Edit: Very nice. By taking off and reseating one bank at the time, I was able to get banks 0/1/2 working but the last bank gives me "0C08 201" error.

Edit2: I tried exchanging bank 3 chips and now it's "0C01 201" error.
 
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If only I could see which chips are failed... I could take some chips from the other computer but testing third bank randomly is not good method. Does the error code 0C01 201 reveal anything significant? I don't have tools to burn eprom with diagnostic program for myself.
 
musicforlife said:
By taking off and reseating one bank at the time, I was able to get banks 0/1/2 working but the last bank gives me "0C08 201" error.

I tried exchanging bank 3 chips and now it's "0C01 201" error.
Click to expand...

musicforlife said:
If only I could see which chips are failed...
Click to expand...
One by one, replace the same chip in bank 2 with each of the chips from bank 3. That will tell you which one(s) is/are bad.

0C08 indicates it is the bit 3 chip.
 
musicforlife said:
If only I could see which chips are failed... I could take some chips from the other computer but testing third bank randomly is not good method. Does the error code 0C01 201 reveal anything significant?
Click to expand...
1. Goto http://minuszerodegrees.net
2. Goto the [IBM 5150] section
3. [RAM information]
4. [16KB-64KB Motherboard]
5. Goto the [POST test of conventional memory] section
 
modem7 said:
1. Goto http://minuszerodegrees.net
2. Goto the [IBM 5150] section
3. [RAM information]
4. [16KB-64KB Motherboard]
5. Goto the [POST test of conventional memory] section
Click to expand...

So 0C01 indicates that it's Bank 3 and "bit 0". What does bit 0 mean?


I bought 16 new 4116 chips because I'm quite sure that the other computer also will be needing replacements ram.
 
Thanks. Now I have got all 64kb working in the machine. However another issue comes now when using memory card:

I have got 2 memory cards, standard ibm 256kb and 512kb, which both of them I tested and used previously in my 256kb model of 5150 without any problems. Now with this 64kb model, 256kb works fine but 512kb brings me always error message no matter what is the added amount by SW2 switch: "108D 201". What does that mean?

Here's my 512kb card which worked perfectly before:
attachment.php
 
musicforlife said:
I have got 2 memory cards, standard ibm 256kb and 512kb, which both of them I tested and used previously in my 256kb model of 5150 without any problems.
Click to expand...
So, both of those cards must have had a starting address of 256 KB.

musicforlife said:
Now with this 64kb model, 256kb works fine ...
Click to expand...
Which suggests that you changed the card's switches so that the card's RAM started at address 64 KB.

musicforlife said:
... but 512kb brings me always error message no matter what is the added amount by SW2 switch: "108D 201". What does that mean?
Click to expand...
SW2 does not add/remove memory. It only tells the 5150's POST how much conventional memory is fitted.

To have this 512 KB card as the first RAM expansion card in your 16KB-64KB 5150, you would need to change the card's starting address to 64 KB. See [here]. I cannot see any switches or jumpers on the card that would allow you to do that.

musicforlife said:
"108D 201". What does that mean?
Click to expand...
Explained at [here]. Failure at address 64 KB. A large number of bit are in error, which often means that there is no RAM at that address.

That is consistent with the 512 KB RAM card not starting at address 64 KB.
 
modem7 said:
Which suggests that you changed the card's switches so that the card's RAM started at address 64 KB.

That is consistent with the 512 KB RAM card not starting at address 64 KB.
Click to expand...

Oh damn, silly me, how couldn't I figure this out even though I knew the 256kb memory switches... this is hilarious.

*facepalm for myself*


So without switches, there's no way to install this memory card into 64kb machine? Somehow I thought that it would automatically check the memory or something.
 
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musicforlife said:
So without switches, there's no way to install this memory card into 64kb machine?
Click to expand...
You could fit a second RAM card, one that can be configured to fill the gap between the motherboard's 64K and whatever address the 512K card starts at.

I find it hard to believe that the 512K card has a starting address of 256K. Because that would put RAM well past the 640K address, up to the 768K address. As shown at [here], that would conflict with the RAM on any MDA/CGA/EGA video card.
 
modem7 said:
You could fit a second RAM card, one that can be configured to fill the gap between the motherboard's 64K and whatever address the 512K card starts at.

I find it hard to believe that the 512K card has a starting address of 256K. Because that would put RAM well past the 640K address, up to the 768K address. As shown at [here], that would conflict with the RAM on any MDA/CGA/EGA video card.
Click to expand...

Well, I don't know. It only worked in my previous machine with 256kb on-board hence the switches were set for full 640kb and I never had anyt issues with any games, mda or cga. Now it gives me error with 64kb. I can't find any info about it.
 
modem7 said:
I find it hard to believe that the 512K card has a starting address of 256K. Because that would put RAM well past the 640K address, up to the 768K address. As shown at [here], that would conflict with the RAM on any MDA/CGA/EGA video card.
Click to expand...
musicforlife said:
Well, I don't know. It only worked in my previous machine with 256kb on-board hence the switches were set for full 640kb and I never had anyt issues with any games, mda or cga.
Click to expand...
Maybe there was some RAM overlapping going on. Example at [here].
 
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