X20/X21 memory specs

[r2d2]

Hi...

I have been looking all over for a forum for thinkpad users/owners but i have not come across one until today.. i might have used a blind search engine then...

it has been my 'sickness' lately to buy thinkpads especially the old X models... and currently i have two... i run linux on them and they are happy with it, i think... hehe..

but i think i need to upgrade the memory. on my x21 i have 256MB and the X20 i have 192MB (including the onboard). my question is... as per ibm website it says there i can use a PC100 144PIN sodimms on them but i have read somewhere that the X20 and X21 will only run low density modules...

any advise on this? do i really have to buy the low density ones (very expensive even in ebay)? or i can just buy any PC100 144pin 256MB module so i can max out what is supported by the bios and motherboard?

thanks in advance

[rkawakami]

You have found the right place; Aloha from Thinkpads.com!

The X20 and X21 systems both use PC100 memory. That essentially means that the maximum you can put in there is a 256MB low density module. That will give you a total of 320MB or 384MB (64 or 128MB on the motherboard, plus the SODIMM slot). The 256MB low density modules can be identified by counting the number of individual memory chips on the board. There should be eight per side; a total of 16. Such memory modules can be found on eBay cheaply if you are patient. If you are not, contact me via PM as I believe that I have one available.

P.S. Here's some good resources for your X20 and X21:

Hardware Maintenance Manual
Drivers and Software

[BillMorrow]

linux should be just happy with 384meg and 256meg..

my little transnote runs W2k fine on 384meg..

welcome to the planetwide thinkpad community..

[r2d2]

Aloha to you too... hey thanks for the replies...

Bill yes I believe so too if ever I can just max out the RAM. Right now both are quite happy with PCLinux on them. I tried to install Fedora but I find it slow with my limited 'resource'. I tried OpenSuse 10.2 but I was not successful as my system hung during install. (Is it already obvious that I am not much of a Windows fan?)

Anyways... so that means I really need the low density ones. Hmmm but why does it not say there in the IBM website... oh well...

Any ideas how much one costs? I am asking this because I have no basis on what is a good price for this type of RAM. In ebay, the new ones (kingston TP390x/256) cost around $45 (buy it now)... is this price reasonable? I was comparing it to the newer ones (DDR and DDR2) and was surprised that the low density ones cost more.

rkawakami, thank you for the offer. I would definitely PM you should my patience run out as for now, I will try luck first with ebay.

Much Mahalo to both of you... Aloha

[rkawakami]

Reasonable? Hmm.. nothing is reasonable when it comes to pricing on outdated memory modules. You are correct that newer DDR and DDR2 modules are cheaper when considering $$$/megabyte. It's a sad fact that as you reach the end-of-life on most every type of semiconductor memory, the price curve starts going up. If you graph the cost of a particular memory component over time, you get what looks to be an inverted bell curve. When a part is first introduced, it cost an arm and a leg. As production ramps up, the manufacturing price goes down, until you get to the point where you are actually losing money for every part you ship. That's when the market shifts to the next-generation product. Meanwhile, the "old design" sits in the price basement until several years go by. Then, due to scarcity (since nobody is making them anymore), the market price starts to increase. Your quoted price of $45 seems to be a little bit on the high side (to me), but it's within the "normal" range for a Buy-it-Now.

The "low density" modules were mostly the only ones around back when IBM was selling these systems brand new. As time went by and the memory densities got, well... denser, there was a change to one of the memory timing specifications. Suffice it to say that you cannot use a "high density" module in a system which was only designed to handle "low density" components. Since older usually means rarer, the prices for low density modules started exceeding high density versions even when the overall module memory size remained the same.

You also have a PM from me.

[r2d2]

Thanks Ray..

I am really wondering why I cannot find that specific requirement (low density 16chip etc...) in the IBM support website. All they say there is PC100 144PIN which for someone like me would understand it as 'any PC100 144 PIN sodimm will do'.

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

I guess even if I update my bios, it still would not support any other except the low density ones (live with it... accept it... ).

[rkawakami]

Well, as to the non-mention of "low" and "high" density modules on the support page you linked to (thanks, by the way!), I can only assume that IBM wanted you to stick with IBM FRU-labeled memory modules. For 256MB PC100 that works in the X20/X21, 600X and similar systems, you are looking at FRU 33L3070. From a sales and marketing standpoint, it's easier to just say that you need a 33L3070 (also sometimes called 33L3069) module. IBM qualifies various memory module vendors and would guarantee that those particular ones would work in their systems. That was then. Today, you will find that other people made or sold PC100 256MB modules which have not gone through the formal qualification process by IBM and thus, can't wear the FRU badge. Those modules will usually work as long as they conform to the standard which was specified by IBM. This is one of the reasons why some 256MB low density modules on eBay command a higher price.; if it has an IBM FRU of 33L3070, people know that it should be fine. In my book any 16-chip 256MB PC100 module will work, as long as it's not some proprietary design like for an Apple (i.e., double height cards).

The "density" we are talking about refers to the memory size of the individual memory chip on the module and is also related to what's called the refresh cycle specification. Sixteen 16MB chips will total 256MB. That's considered "low". It turns out that 16MB memories were designed to operate under "4096 (4K) refresh cycles". Eight 32MB chips can also be a 256MB module (a "high" density one) but because those parts were designed a little bit differently, the refresh specification is "8192 (8K) refresh cycles". If the laptop is using a chipset that is fixed to generate 4K refresh cycles, you can't plug in a module which uses 8K refresh parts. The opposite however, is not true. You CAN use low density modules in a system which normally expects to see high density modules.

Confusing? Yes, but fortunately there's only a couple of "gotchas" when dealing with memory.

As to a BIOS update, I don't believe that can be used to alter the basic memory timing system, a component of which is the number of refresh cycles being generated. I believe that is a product of the Intel chipset being used. In the case of the X20/X21 it's the 440ZXM.