This T21 won't recognise memory above 256MB.

[KaoSM]

Hi all,

I am trying to upgrade the memory on a T21 2647 9AG. It is currently running 256MB on two sticks of 128MB PC100 144Pin SODIMM.

I recently purchased a stick of 256MB from Crucial.com to check see if it would take it. The memory finder on the web site ID'd the right memory apparently, yet when I put it in with either of the other sticks in any slot combo, the BIOS on boot up only recognises 256MB!

I tried flashing the BIOS to the latest ver yet it still won't recognise any higher.

The only problem I can work out might be that the stick of 256MB is PC133 not PC100, but I thought it wouldn't matter as it would simply run at the slower speed as I have done with PCs before.

This is my first time on here (New member). Can anyone help?

Thanks in advance and respect to knowledge,

Regards,

Sean M

[joester]

Welcome to the forum, Sean!

I believe you need to have matched RAM. The T21's won't allow PC100 and PC133 sticks to play together.

If one of your 128MB's was PC133, I bet it would work fine, and recognize all of it.

Joe

[rkawakami]

The T21 requires the use of what is normally termed "low density" memory. You can basically identify a module with this characteristic by counting the number of memory chips (on both sides) that are installed on it AND knowing what the size of the module is:

256MB module:

- 16 memory chips = low density (will work in a T20, T21 or T22)
- 8 memory chips = high density (will not work in a T20, T21 or T22)

128MB module

- 8 memory chips = low density (will work in a T20, T21 or T22)
- 4 memory chips = high density (will not work in a T20, T21 or T22)

All things being equal, the module's speeds (PC100 and PC133) will not matter if they are different. The system will only clock the memory at PC100 timings. As long as the PC133 module has the proper information set in a special memory chip that says it can also operate slower than "normal", then all should be good.

My bet is that your 256MB module is a high density version (8 chips).

edit: Additional note... there are some "weird" looking low density 256MB modules out there that only appear to have four blobs of black plastic on them. Unless you know the specific part number on them or the seller offers a guarantee that they will work in your particular situation, I'd say don't bother with them.

[KaoSM]

Hey guys!

Thanks for the mega-fast response! I'm impressed!

Well now the density of the memory I never considered - nice one. I must say that the stick is indeed High Density based on the fact that it has 8 chips on it (4 each side).

So the question is now: Where is best to look for what I'm after? Any ideas? Or should this question be in a different post?

Regards

Sean M

[rkawakami]

256MB PC100 (or PC133) modules approved by IBM for use in T20-T22 systems will have a 33L3069 or 33L3070 FRU on them. Crucial should carry this type of module; return the one you have and tell them to fix their memory selector guide . Don't know off-hand what the Crucial part number is but you can look for "MT16LSDF3264HG*" on eBay (no quotes, the asterisk matches anything after the "HG"). That's the Micron part number for the identical module that Crucial should sell.

Expect to pay somewhere around $45-$55 for one, online from any major memory dealer. More for those really trying to rip you off. eBay prices for these things hover anywhere from $5 (I was real lucky!) to around $30 if you are patient.

edit: BTW, I'm planning to snipe a lot of those Micron modules...

[KaoSM]

Right ok. I will get onto crucial today and arrange a return if possible. I'm sorting this out for a friend and I really like the sound of the sniped ones...

Perhaps you could mail me if you get any luck - I'd be interested in a stick of 256!

Big thanks for all your help guys!

I think my problem is over...