Cheapest Place to Buy PC100 256MB RAM?

[NTL1991]

Does anyone know of the cheapest online store/store to by a stick of PC100 256MB RAM for my T21 (2647-4AU)?

Thanks,
Nick

[pianowizard]

Look for "33L3069" or "33L3070" on eBay. Second cheapest is 18004memory.com.

[richp]

Send me $20 and I'll mail out my 256meg stick I just pulled from my T30, it was the original stick that came in the refurbed one I just bought last week. I stuck 2 512's in there.

[rkawakami]

Uh, the memory out of a T30 will not work in a T21.

[richp]

Uh, the memory out of a T30 will not work in a T21.

Darn, sorry, not real familar with the TP's and what to feed them.

[rkawakami]

T30=DDR PC2100 (266Mhz) CL2.5 200-pin module.
T21=SDR PC100 (100Mhz) CL3 144-pin module.

Won't fit .

[furiousmonkey]

well cant you jam it in?

Just kidding, my T21 is running PC133 ram, low density, it is running at 100 though, just an FYI. Works beautifuly.

[phool@round]

After a quick check on the world's finest flea market, @ $20 on average for PC100/133 256Mb. That's Ebay retail of course YMMV. I'd go half that....shipped!


Actually for $20 I'd buy the module IN the T21. Ebay-a-holic....my apologies.

[pianowizard]

After a quick check on the world's finest flea market, @ $20 on average for PC100/133 256Mb.

But be careful, most of them won't work because they're high-density.

[phool@round]

So true, so true. I did a pretty thourogh check fortunately. But that's me and not Nick. Quite a few Ebay listers don't know the difference or didn't state it. I was rather peeved that a search for low density only turned up a few hits.

As long as the photo is of the actual object being sold........it's easy to spot if someone knows a thing or two..........so on to the lesson.

For those that don't know what low density is.......

Nearly 99.9% of the time a low density (PC100/133) 144 pin SoDIMM will have just 4 chips per side. The chips are rather tall if you compare to the module hold down notches and the inter connects are visable to the sides of the chips. http://www.pcs4u.com/store/pics/sodimm.jpg

Here is a High Density module (PC133): http://www.macrotronusa.com/usa2003/images/sodimm1.jpg Notice the lack of inter connects? That is because they are UNDER the chip and not along the sides.

Noticable difference but read on.

In a 256Mb PC100 module we are looking at 4 chips per side, each individual chip will be equal to 32Mb in size. So, 4X32Mb = 128Mb per side. For a 256Mb module, both sides will be equal, 128Mb plus 128Mb on the other side for a total of 256Mb. In a 128Mb chip the 4 chips are 16Mb each or 32Mb each but only on on side. (Rare but out there.)

So for a low density PC100 144 pin 256MB memory module we are looking for a 8X32 module which is what IBM states will work in a T21. When reading the fine print in the sellers specs wether brick and mortar or not we are looking for a PC100 8X32 144 SoDIMM module. If you come across a 16X16 it is high density BGA module.

Again most Ebay listers are in it for the income and not for the information.

Fortunately @ 75% of the ones listed on Ebay are in fact low density, I double checked just to be sure as not to confuse anyone or myself. (Many with IBM stickers on them. Can you say Thinkpad off lease flood.)

High density in the case of a 256Mb module would be 8 chips of 32Mb *all* on one side (or 4X32 each side but noticably shorter in comparison to the holder notch, length of chip comparison.) It looks sort of like this: http://en.wikipedia.org/wiki/Image:BGA_RAM.jpg Which is either a 256 or 512 module and probably PC2100 by looking at the slot, sorry best I could find under short notice......

Thank you pianowizard for holding my feet to the fire and who I envy for his S30. (I read more than I post.) I hope this helps Nick and anyone else that didn't know. Not all inclusive but a good starting point for those who wish to educate themselves.

[NTL1991]

Thank you very much phool@round for that very valuable post! I guess I just have to find one at the right time. One I was watching on eBay closed at 32 bucks plus around 5 dollar shipping...

These PC100 256MB Chips are in very high demand, I might guess.

Thanks Everyone,
Nick

[pianowizard]

Fortunately @ 75% of the ones listed on Ebay are in fact low density

Does this percentage include PC133 sticks, or are you just referring to PC100 ones? I've always thought that the majority of PC133 modules are high-density, which was why I urged the OP to be careful.

Thank you pianowizard for holding my feet to the fire and who I envy for his S30.

No, I don't own an S30. I wish I did! I have written numerous times about my admiration for the S30 though, which might be why you thought I actually own one!

[rkawakami]

Nearly 99.9% of the time a low density (PC100/133) 144 pin SoDIMM will have just 4 chips per side. The chips are rather tall if you compare to the module hold down notches and the inter connects are visable to the sides of the chips.

That depends upon the total size of the memory module (128MB, 256MB, or 512MB, for example). The physcial size of each memory chip does have a little bearing on the "density" of the module, but it's not so simple. I'll get to this in a minute...

Here is a High Density module (PC133): <snipped link> Notice the lack of inter connects? That is because they are UNDER the chip and not along the sides.

The placement of the individual component's leads (I guess what you are calling the interconnects) does not have anything to do with the "density" of the memory module. It is merely a different packaging technology. The ones "to the sides" are called TSOP (thin, small outline package). The ones with the contacts underneath are BGA (ball grid array). Placing the silicon memory chip inside a BGA package does not automatically mean you have "high density" memory. The selection of TSOP vs. BGA packages has more to do with the internal memory architecture (the number of output pins on each device) and the cost/size benefits of putting the silicon die in each package.

In a 256Mb PC100 module we are looking at 4 chips per side, each individual chip will be equal to 32Mb in size.

Correct. This type of module is generally known as the "high-density" version. The use of 8 32MByte memories makes it so.

So for a low density PC100 144 pin 256MB memory module we are looking for a 8X32 module which is what IBM states will work in a T21.

If by "8x32" you mean 8 32Mbyte chips, then that is not correct.

When reading the fine print in the sellers specs wether brick and mortar or not we are looking for a PC100 8X32 144 SoDIMM module. If you come across a 16X16 it is high density BGA module.

Incorrect. 16 individual 16Mbyte memories is "low-density".

High density in the case of a 256Mb module would be 8 chips of 32Mb *all* on one side (or 4X32 each side...

Correct.

...but noticably shorter in comparison to the holder notch, length of chip comparison.)

Again, the physical size may not be a true indicator of the "densityness" of the memory. What really matters in the distinction between low and high density memory, is the use of 16MB (low density) or 32MB (high density) chips.

In short, if you go by these rules, you should be able to tell the difference (these examples are for PC100/PC133 SDRAM):

- 256MB module: 8 chips = high density, 16 chips = low density
- 128MB module: 4 chips = high density, 8 chips = low density

[phool@round]

Thanks Ray and pianowizard, you two are amoungst the many regulars that make this a great place to learn and enjoy Thinkpads. Honestly. I enjoy this more than Christmas, well almost. This lasts all year......though.

Pianowizard, you brought out a fact that what's in a category might not rightfully belong in it. No one should assume that what's listed is in the buyer's interest and knowledge prior to buying is important. I also realized I have tunnel vision when it comes to Ebay..........I weed out what I'm not looking for, zone in to what I am. There is no doubt. All memory in the PC100 SoDIMM category *should be PC100. I did an explicit search and what it turned up wasn't all PC100 for sure. Buyer beware when it comes to Ebay especially to those that aren't sure. I would reeeaaaallllllyyyy like to find an S30...... and a Transnote and an X24 in perfect condition.......maybe still in the box!


Ray, I rely on your input more than you might imagine. Like the light emitting transistor, man that was funny....... My RAM experience has so far been with faster modules PC2700 and above. I recently decided to go old school in the last couple of years. Tired of trying to keep up and enjoy what was too expensive back in the day, relive a little of the past. I'm starting to slow down.... The T23 has shown me a thing or two about older RAM technologies, it has shown me what to look for, mostly high density 512Mb modules which are very expensive everywhere. So I'd have to say that I'm learning right along with everyone else and don't mind being the sacrificial lamb in this discussion to help point out what's what. I hope it helps those who don't honestly know. I think it will. It has for me. Maybe there's a T21 in my future........ off to Ebay I go.......