A20m Memory Issues

[tm512]

Hey all, new to this forum. I got a "new" ThinkPad A20m a while ago and after some issues (the intermittent shutting down) I have a nice system running Ubuntu 9.04.

Now to my question, it has 256MB of memory installed, but only 128MB is recognized. If I take either SO-DIMM out, it will recognize the full capacity of it and show as a total of 128MB. Any suggestions? Also, when I put a 32MB SO-DIMM in I will get POST beeps, but I've been told that it's because the 32MB might be PC-66. Thanks in advance.

[RealBlackStuff]

Welcome to the forum.
Please give us the 7-character TYPE-MODEL no. from the bottom of your laptop.
Also give us all the info you can find on both RAM modules.
They may not be compatible with one another.
Have you tried swapping them around?

[tm512]

Please give us the 7-character TYPE-MODEL no. from the bottom of your laptop. Also give us all the info you can find on both RAM modules.

"TYPE 2628-G9U"

Stick 1: Toshiba, PC100-222-620, 16Mx64 SDRAM
Stick 2: IBM certified Infineon, PC100-222-620, 16Mx64 SDRAM, 128MB, Sync, 100MHz, CL2

And I have swapped them around. I don't know what's happening.

[RealBlackStuff]

Your laptop is an A21m, and it needs PC133 SDRAM SODIMMs, not PC100.
It can take 2x 256MB = 512MB total.
see e.g. http://www.crucial.com/store/listparts. ... %202628%29

[rkawakami]

A2x systems, "m" and "p" included, should be able to accept PC100 modules as long as they are of the "low density" type. For a 256MB module, that means 16 individual memory chips on the board and for a 128MB module it's 8 chips.

ref: http://www.lenovo.com/psref/pdf/tawbook.pdf

edit: To clarify, a PC133 will also work as long as it's a "low density" version. It's not necessary that you use PC133. I have an A22p right here with two PC100 modules (256MB and 128MB).

[tm512]

Your laptop is an A21m

No, it's an A20m.

For a 256MB module, that means 16 individual memory chips on the board and for a 128MB module it's 8 chips.

Each of these 128MB modules have 8 individual memory chips.

I really want to figure this out so I won't have to rely on swap so much, it's a really slow computer at the moment, even though I'm using a lightweight window manager, an I'm using Chromium instead of Firefox.

[rkawakami]

Given the TYPE number, 2628-G9U, that resolves to an A21m according to this:

http://www-307.ibm.com/pc/support/site. ... y=2628-G9U

The base or the clear plate (where is says "A21m or A20m") above the keyboard may have been swapped out previously in its life.

The best thing you can do right now is only install one module and run a memory diagnostic like memtest86+:

http://www.memtest.org/#downiso

Once your system is booted with the memtest86+ diskette or CD, the display should indicate the amount of memory it has found; about the fifth line down from the upper left, "Memory : xxxx". Let the diagnostic run at least for three complete passes (count is under the column titled "Pass"). Assuming that it passed, shut down the system, move the module to the other memory slot and run the tests; one complete pass should do - you are only checking to see if the slot has a problem. This will verify that that one module is working correctly and that there's nothing wrong with either memory slot. Again, assuming the the module passes, remove that module and install the second module (either slot) and run three full sequences through the tests.

[tm512]

I have pinpointed the problem and am confused as to why I didn't recognize it before. One of the slots will give POST beeps if the only stick is in that slot, so basically I can only have half of the Thinkpad's full RAM capacity.

It can take 2x 256MB = 512MB total.

According to lshw or some other hardware info utility it says full capacity is 1GB. So, which is it?

Thanks for the help.

[ajkula66]

You have one bad memory slot, so your machine will only take 256MB of RAM, not that much in today's day and age.

All A2x series ThinkPads max out at 512MB with both slots operational, no ifs, ands or buts there...

Good luck.

[tm512]

Okay, thanks for the help.

For the record, has anyone actually tried a 512MB SO-DIMM in a Thinkpad A21m?

[rkawakami]

I believe that there are no "standard height" (~1.25") 512MB PC100 or PC133 "low density" modules in existence. If you plug in a "high density" 512MB module you will either get a boot beep error code or the system will only recognize 256MB.

[ajkula66]

Agreed with Ray. I've tried 512MB PC133 SODIMMs on several A2x systems in the past and got no boot on any of them, to the best of my recollection, although this was a few years ago.

I've never seen a 512MB PC100 laptop SODIMM, or heard from a trustworthy source that such an animal exists.