T21 Memory problem with 2x256MB sticks

[woolbeo]

I am having memory problems when I install 2 256MB memory sticks in my T21, but it works fine if I only have one installed in either memory slot, or 1x128MB and 1x256MB. 2x256MB passes memtestx86 fine, but XP BSODs and linux segfaults. I'm running the latest bios(KZET34WW (1.16)). The memory is 16Mx8 PC133. Any help would be greatly appreciated.

[GACrabill]

If you do some searches on this forum, there are more than a few references to the fact that the T20, T21, & T22 must have PC100 memory. Only the T23 calls for PC133.

[woolbeo]

I have searched the forums. While the T21 doesn't require PC133, it can use it, and even some of the memory that IBM recomends is PC133. The requirement that the T20, T21, and T22 have are atleast PC100, and low density(that is 256mb sticks must have 16 chips, and not 8 higher density chips, i.e. 16Mx8). The problem is not that the ram doesn't work. The problem is that it wont work with two 256 mb sticks.

I have tried the the ram in my brothers T21 laptop, and it works fine with both sticks installed.

[verktyg]

Everything that I've seen says that the T20-T22 TPs use PC100 memory and they will choke on PC133 (a lot systems will when you try to mix PC100 & PC133). There was some questionable quality PC133 memory when that type was current that was jacked up to run at the higher speed but was actually only PC100 capable memory.

I recently upgraded my T20 to 512MB - 2 x 256MB. I bought one IBM 256MB 16 chip low density PC100 SODIMM that checked out OK in other systems but wouldn't play nice in my T20. No boot, no POST. I replaced it and all is well.

[beeblebrox]

You can use PC133 memory in the T20 series. Faster is no problem, because they will be dirven by the slower clock.

The problem is the Intel chip set that has a different arrangement of addressing the memory matrix. The first series of it needed the "so-called" low-density matrix with 16 chips. PC100 or PC133 doesn't matter.
Your problem with the IBM stick is a problem of the CAS (Column adress strobe), which can differ vastly. The better chips can use CAS2, if they are slower they go up to CAS 3 (and are cheaper).
If you mix the memory, the chipset can get problems with the different access times.

[JHEM]

While the T21 doesn't require PC133, it can use it

No, it doesn't play nice with PC133 RAM. Search eBay for "33L3070", that's the PC100 lo-density RAM you need.

and even some of the memory that IBM recomends is PC133

Sorry, no they don't!

http://www-307.ibm.com/pc/support/site. ... MIGR-55644

I have tried the the ram in my brothers T21 laptop, and it works fine with both sticks installed.

Model number of this magic Thinkpad? What OS is he running?

Regards,

James

[JHEM]

You can use PC133 memory in the T20 series. Faster is no problem, because they will be dirven by the slower clock.

Sorry Zaphod, but you're wrong!

The T20, T21 and T22 all suffer brain farts with 256MB PC133 memory UNLESS it's lo-density and those are apparently as rare as hen's teeth.

I've been told by several knowledgeable folks that lo-density PC133 memory exists but I'm still waiting to actually see any.

Regards,

James

[verktyg]

James,

There is one highly unlikely possibility - when PC133 first came out there where some shady memory fabricators that jacked up the Eproms so that PC100 memory would run at PC133 speed but not well. This issue was reported in some of the Desktop News Groups.

[woolbeo]

Sorry for the long delay in replying. School, work, and life have all been really busy, and I didn't want to post anything untill I found out the problem.

First off I am using low-density PC133 256MB cas 2 sticks, i.e. 32X64/16X8(8 chips per side, for 16 total chips).

It turns out I have a bad memory slot. I started having problems with one of the 128MB sticks when I had 2 x 128MB installed. It started segfault/BSODing, and then on the next reboot it wouldn't even recognize the ram. So I took the ram from the slot that was working, and put it in the other slot, and it had the same problem.

I do not have my brother's T21 that both sticks work fine in, and he lives far away, so I can't get the model # of his "magic thinkpad."