Thinkpads Forum

I found this auction on E-bay for 512MB PC100 LOW DENSITY RAM.

Will these work in our 600's? I know we need low density, but i thought the highest we could go was 256MB sticks? What has me puzzled is that the description claims it works in a T20. From what i have read in the TX forums, thos machines are very similar to the 600X machines in that they max out at 2 x 256MB sticks. So if this module supposedly works in a T20, it should work in a 600X, right? Or maybe its just a misprint in the description?

http://cgi.ebay.ca/ws/eBayISAPI.dll?Vie ... :IT&ih=018

Run, don't walk away from that one. He's advertising "Samsung" module with a picture of a Micron (yes, I know that he correctly states Micron in the auction description). Also, the picture is of a 256MB module, which IS low density for that size of module (16 chips).

edit: Sorry, to answer your question, yes, they will work in the 600 and T20-T22, but it will only be 256MB. As far as I know, nobody ever made a 1.25" tall, 512MB low density PC100 or PC133 module.

Yeah, about the picture, I meant to say something about it, but he does have the disclaimer about the picture not being the ACTUAL product, yadda yadda yadda. I recognized the ram in the picture immediately as a 256 stick. I guess I was just more interested in knowing if there was such a thing as low dinsity 512 sticks? If it supposedly works in a T20, it should also work in a 600X. So my guess is it was a misprint and it should be advertised as a 256 stick?

Thanks for the reply though.

I found another seller who claims to have 512MB Low Density PC133 sticks:

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0202276819

Again, picture is not of actual item. Especially as it only has 4 chips per side

And another one here:

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0187397239

And here:

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0195758012

And here:

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0202196395

and finally, here:

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0193959338

All the info I have read in these forums on the 256MB low density sticks is that they had to be 8 chips per side for a total of 16. If thats the case, for these to be a TRUE low density stick, would it HAVE to have 16 chips on each side (not that that would be possible on a low profile stick)?

Moderator edit: Shortened URL to prevent horizontal scrolling

There's is some (??) confusion among eBay sellers as exactly what constitutes "low density". Some (correctly) describe it as having 16 chips on a 256MB module, while others would say that an 8 chip 512MB module is "low density" simply because it's not a 16 chip version. In that case, "low" is describing the number of chips on the module.

To precisely describe the differences between "low" and "high" density modules of 256MB and lower size, it's really the case of what type of refreshing is being used (4,096 cycles [4K] for low versus 8,192 cycles [8K] for high). The T20-T22 and 600 systems require the use of 4K refresh devices. Since 16MB DRAM parts had that specification, you need 16 of them to make up 256MB, and eight for a 128MB module. When the industry conceived of 32MB DRAM parts, they had to increase the refresh spec to 8K. So you can build 256MB modules with eight 32MB parts, but because of the difference in the refresh specification, they won't work on the older PC100 systems.

edit: And yes, a "low density" 512MB module would require 32 parts on the board. It's not out of the realm of possibility since I believe that some Apple systems can use "double height" SODIMM modules (i.e., taller than the "normal" 1.25 inches). I've just never seen one.