PC100 256MB 8 chip low density module exists

[rkawakami]

Here's some interesting and important information concerning low density 256MB PC100 SODIMM:

Not all 8 chip modules are "high density"!

Said another way, there is at least one 256MB PC100 SODIMM that only has eight devices which can successfully be used inside a 600E, 600X, T21, A22 and probably any other "low density" system.

This thread: http://forum.thinkpads.com/viewtopic.php?t=67488 got me thinking about the claims of the eBay seller "1-800-4-memory". This seller has been mentioned here several times as being a good source for memory. They are offering this:

33L3069 modules

If you look at the picture they have it shows a module that has 4 chips on one side (and one can safely assume that it has 4 more on the other side) and a label on it which says "256MB SDRAM PC100 144pin LOW DENSITY". There's also a compatible Thinkpad systems list which includes PC100 equipment. Since they stated that they guaranteed that the module would work inside these systems and referenced the correct IBM FRU (33L3069), I bought one at $30. That's a little bit high in my book since I'm cheap, but this was a science experiment .

Arrived in three days in a small padded envelope via USPS First Class with Delivery Confirmation (shipping was "free"). The module I received looked exactly like the picture in the auction description. Put it inside a T21, booted a memtest86+ CD and it registered 256MB and passed! Installed the module in an A22p and it worked there as well. Even when combined with a low density 128MB or 256MB module, everything passes. Putting the module into either slot of a 600E (2645-8AU) and running the Easy-Setup memory test, it fails with the memory error code of:

DEV 002
ERR 83
FRU 2010

However, when booted to a memtest86+ diskette, it recognizes 288MB (256MB + 32 on board) and passes (!!??! - still trying to figure this one out ). Details about the module and my testing are here:

http://www.kawakami-ca.com/8_chip_low_d ... mb_sodimm/

Currently there's only the pictures I've taken of the module and memtest86+ test results. I'm planning to take the module to work on Monday and use the bench-top tester to get some more information about it. For now, these are my assumptions:

- the eight parts are 16M x 16 devices; i.e., 16M addresses and 16 data pins or 32MBytes total
- the refresh rate is 4,096 cycles every 64mS
- CAS latency might support CL2, based upon the parts being marked for 133Mhz (-75)

I've tried to get the datasheet on the individual memory component but so far have come up empty. They appear to be sourced from SpecTek, a company owned by Micron:

http://www.spectek.com/

but the part numbering system has changed a couple of times in recent history and the current part numbering system does not cover this particular device (S160032LLLTK-75A). The closest that I can get says the parts are 32M x 16. However, if there are 8 of those on the module, then the total memory size would be 512MB! And at the same time, the part number suggests that these are 8K refresh devices; what I would consider high density. Compounding my confusion, an apparent date code on the packages would lead me to believe that these parts were manufactured around June of this year.

[Harryc]

Thanks for the detective work Ray. It's always nice to have an alternative source for RAM on these older machines.

[fixup]

Thanks for the test, I just bought one for $25.

I've been looking for a 256MB for my X20 (2662). I've tried two, both are 8 chips, both show 128MB only.

It is ridiculous to spend $50 for 256MB for a laptop I bought for only $100. Hopefully this $25 one will work.

[fixup]

Got the 256MB RAM today, put it into my X20 and it works like a charm. Yes it is 8 chips total.

[rkawakami]

Okay, I finally got my web site updated with the results of the bench-top tester analysis.

Here's the short scoop: It's really a 512MB module that's been modified to identify itself as a low density 256MB version.

The long story is on the web site. Hope your eyes don't glaze over .

[fixup]

Wow, I never thought that, even though I've tried two 256MB that appear to be 128MB only. So, we might just buy a 512MB!

[fje]

Okay, I finally got my web site updated with the results of the bench-top tester analysis.

Here's the short scoop: It's really a 512MB module that's been modified to identify itself as a low density 256MB version.

The long story is on the web site. Hope your eyes don't glaze over .

Hi, Ray, good work ! but... where in your web site is the story ? I had a look to the site, but couldn't find the ref.story....

Rgds.

[rkawakami]

The site: http://www.kawakami-ca.com/8_chip_low_d ... mb_sodimm/

The long story I'm referring to is the 7 screen captures from the tester I used and the detailed explanations of what I found stored in the SPD bytes. If you had previously visited that site but only see the 10 photos of the module and memtest86+ results, then force a refresh in your browser as you may be seeing a cached version.

A quick summary of the long story: A couple of the SPD bytes have been altered so that the 512MB high density module "looks like" a 256MB low density version.