RAM question 2645-51U

[ms5133]

I'm still somewhat confused about maxing out memory on this unit.

I understand that 416MB can be achieved with 2x256MB pc100 low density in that 1 chip is only read as 128MB.

Can you get 544MB with 1x256 pc100 plus 1x256 PC66(if it can be found)

Can you get 416MB with 1x256 pc100 plus 1x128 pc100

Can you get 416MB with 1x256 pc100 plus 1x128 pc66

Does the memory need to be CL2?

[rkawakami]

This question has also been on my mind as well. So much so that I've been looking on eBay for a cheap 51U system to experiment on. These threads:

http://forum.thinkpads.com/viewtopic.php?t=24244
http://forum.thinkpads.com/viewtopic.php?t=30080

and probably a few other that I can't find at the moment, have some information in them which says that only 256MB PC66 modules are usable in the 2645-51U. I'd like to be able to try a couple of PC100 modules and see what happens. I have access to a memory module tester at work which can alter the SPD information. Maybe there's something in there that can be changed on PC100 (or even PC133) low density modules which will then let them work inside the 51U.

edit: re: "CL2" It probably would be best if you try sticking with CL2 modules as that would mean it can operate at CL3 timings as well. I don't know what the 600 uses (expects) as the system timing but CL2 is probably a good guess given the speed of the memories in those days. And I guess this is a formal announcement that I'm lurking on eBay and will snipe at a reasonable system .

[Wingnut]

Can you get 544MB with 1x256 pc100 plus 1x256 PC66(if it can be found) YES

Can you get 416MB with 1x256 pc100 plus 1x128 pc100 NO

Can you get 416MB with 1x256 pc100 plus 1x128 pc66 YES

I can tell you for a fact that my 51U would read all of the 256, pc100 stick if it was in slot 2, but only half of it in slot #1 (the closest to the CMOS battery).

I tried the same thing with a 128, pc100 stick and the results were exactly the same, all of it in slot 2, half of it in slot 1.

In order to max out my RAM, I had a 256, pc100 stick in slot 2 and a 128, pc66 stick in slot 1. Add the 32 built in and I got just over 420mb. If you can find a 256, pc66 stick, you should be able to max it out at 544.

[ms5133]

Ray, I can vouch for 2x256MB PC100 sticks in my 51U, again with slot 1 reading half the memory giving a total for 416.

Wingnut...so slot 1 has to have a PC66 chip for it to be read at full value.

Any hints on where to find a 256MB PC66 chip? (none that I could find on E Bay)

[Atlas64]

If ya want i have a perfectly working 51u siting right here in front of me. It's just missing a battery and has a faulty cdrom. if your interested pm me

[Wingnut]

Wingnut...so slot 1 has to have a PC66 chip for it to be read at full value.

I can't say that for an absolute fact, but it has been what I have experienced. PC66 128mb sticks are easy to find and relatively cheap, so buy one and try for yourself. But when I tried them in my 51U, it read 128 in both slots. But when I tried the PC100 128mb stick, it read only half in slot one and all of it in slot 2. I can only assume that the same would be true of a pc66 256 stick????

[rkawakami]

Prey sighted and taken down for $38 :

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0165853741

Hoping that the 192 error is simply a bad/weak CMOS battery. If not, then I have some spare pieces which can go into a couple of other 600 systems I have under the desk and I'll be back on snipe patrol.

The plan is to take a PC100 module and see if I can change the SPD information so that it reports itself as a PC66. I'll then plug it into the 51U and see what happens.

[rkawakami]

600 system received yesterday (Friday). It turns out to be a 2645-45U but all of the low density PC100 modules I've tried in the "front" slot (#1, closest to the Ultrabay opening and the CMOS battery) are only registering half the amount. Put those same modules in the rear slot and the BIOS sees the whole thing. Both 128MB and 256MB low density modules are affected the same way.

I did notice that the serial number and UUID have been blanked out in the BIOS. The motherboard must have been changed at some point. The FRU is 10L1708 which is not found at IBM/Lenovo Support, nor listed in the 600 HMM, but it does appear in some eBay listings. Since this is my first 600 system I have nothing to compare it against. CPU is 300Mhz (reported by memtest86+, as well as in the BIOS) and all of the built-in diagnostics have passed. I guess that should have tipped me off since a 51U is supposed to be a 266Mhz system. Oh well, the "half a memory" problem is evident in this system so hopefully whatever I find out about this 600 will be applicable to the 51U.

And the 192 (fan) error? As I thought, it was due to a bad CMOS battery. In fact, somebody had created their own replacement by soldering the peeled-off tabs to a regular CR2032 battery and then taping it up ! The voltage read 1.1V so I popped a fresh one in, reset the date and time and power cycled the system.

After the memory experiments are completed, I guess it's about time I learn how to install Linux on one of these puppies...

[ms5133]

Awaiting results with bated breath!!!!

As an aside..I had a couple of 64MB PC100 chips laying around, and on a whim I installed each of them in slot nbr 1 , and lo and behold, they are read as 64MB.

So I now have 352 MB PC100 memory...all read 100%. (256 + 64 + 32)

The PC100 64 chips are:Micron MT4LSDT864LHG-10EB1
and Infineon HYS64V8200GDL-8-C2 (FRU 20L0264)

What is the rationale behind 64MB PC100 chips functioning and 128/256 PC100 chips not?

[Atlas64]

Im also confused on this model. Right now i've got 1 128pc100, and 1 128pc66. It's only reading 64 mb out of the pc100. so does only one module read half of pc66, so if i switched the chips around could it read the all of the pc100?

[rkawakami]

It's only reading 64 mb out of the pc100. so does only one module read half of pc66...<snip>

Yes, it appears that if you have a PC100 module (of 128 or 256MB size) in the slot closest to the Ultrabay opening, the system will only "see" half of it. Verify that this is the case, and if so, swap the modules around to see if you increase the memory to 288MB (32MB on board + 128 in front + 128 in back).

[gator]

wow ... awesome purchase Ray ... intersting to know that the 600 series have this "feature" with the RAM slots. I'd have never found this out with my 600X, you know why

If you want info on installing debian/ubuntu/DSL on this machine let me know ...

[Atlas64]

ok, i did the switch and it read or saw the full 128 pc100 and the 128 pc66

[rkawakami]

Okay, first attempt at SPD byte editing has resulted in total failure . I had three PC100 modules which I tried changing to PC66 and all three did not want to accept the re-write command. Don't know if this is a problem with our memory tester or if all three modules have been write-protected. An EEPROM (a non-volatile memory) on the module holds the SPD bytes. It can be permanently write-protected at the factory, in order to prevent what I'm trying to do. I've emailed one of the techs at work to see if she has any old "control units" that we would have kept as standards. Hopefully if I can't find some more PC100 or PC133 modules in my inventory that I'm willing to sacrifice, she'll have some.

For the technically minded and curious folks, I'm trying to change byte 126 from "64" (100Mhz) to "66" (66Mhz):

http://www.memorytesters.com/ramcheck/rc_ap3.htm

This might not actually do the trick, depending on whether or not the 600 looks at this byte, but it's the easiest one to change without disturbing the rest of the timing parameters in the SPD.

[ms5133]

Ray,

Why then does the 600 read pc100 64MB chips@100 %?

Is there some basic difference in the chip structure between
PC 100 64MB and PC 100 128/256( Aside obviously from the capacity)?

[rkawakami]

About the only thing that may matter is the number of banks on the module. There are several control and clock signals being used which can select a whole group of individual memory chips. I'm hoping that this isn't the case since you can't change the way that the parts are connected on the module. The 64MB module that I received with the 600 was a single bank. I think it is a PC100 module; my notes are still at work. The 128MB and 256MB modules that I used yesterday are two bank modules and are PC100. I don't know if PC66 256MB are single or dual bank modules. My gut feeling is that once the jump was made from 64MB to 128MB and larger, the boards were laid out for two banks of memory. That's why it's confusing to me why PC66 256MB are said to work, whereas PC100 256MB do not.

[rkawakami]

From the testing I was able to do last night, it's beginning to look like the number of banks on the module is what matters to the 600. I found some Micron 256MB PC100 modules (MT16LSDF3264HG-10EE4) that were not SPD locked and so I was able to change some of the bytes around. However, nothing I did to those bytes would allow the 600 to use all of the memory. Checking in the BIOS, the amount of installed memory reflected the correct total, but the amount of usable memory was always half of what's in the front slot. This has been reported here before so that's nothing new. What I was able to do is change the byte in the SPD which tells the system how many banks are on the module. When that byte was changed from 2 to 1, the amount of installed memory matched the amount of usable memory (but it still was only using half of the memory that the module actually has). In a sense I told the 600 that what I plugged into the front slot was a 128MB module, not a 256MB. I think what that means is that the laptop is looking at this particular byte when determining how much memory has been installed, but ignoring it since it seems like it cannot deal with a dual bank module in the front slot. And yes, I did try disabling the internal (motherboard-mounted) 32MB of memory. It did not help.

At this point I believe that if I can find a single-bank 256MB low density (4K refresh) module, it will fully work in the 600. It's possible that the early 256MB modules were constructed like that which may account why some modules (specifically, PC66) work while others don't.

If anyone has a 600 system with a 256MB module in the front slot that is fully recognized by the system, I would appreciate it if you would contact me so I can get some information (part numbers) from the module.

What exactly is a "bank"? Essentially, it's a way to select a whole group of parts at one time with a single control signal. You might think of it as an extra address line but it is more involved than that.

Does having parts on both sides of the module mean it's always a dual bank design? No. It depends upon the type of memory parts, and by that I mean the number of address lines and data pins, and how they are interconnected on the module. For a single-bank 256MB module using 16 devices, each device would have to be a 32Meg address x 4 data pin part. This is somewhat of a rare part since most parts today being used on a module are x8 or x16 data pin devices.

The way the math works out is this: since the SODIMM module has 64 data pins by design, having 16 x4 parts on the module means that each module data pin has only one device data pin connected to it, and therefore one bank of parts. Assuming that the module has 16 x8 parts, you then have a total of 128 data pins from all of the devices, but only 64 places to connect them on the module. That means each one of the module's 64 data pins must have TWO device data pins connected in parallel. Since you can't have them active at the same time, you have to have separate banks.

I'm going to be digging around work (and the net) in the next couple of days to see if I can find some documentation on early SDR modules. Sorry for the long post but I hope this was clear. It's bedtime...

[ms5133]

As usual , insightful and informative comments from Ray..Thanks..

Any usefull info here, Ray?

http://www.amazon.com/SimpleTech-STA-MA ... 81-9781746

[rkawakami]

Actually, yes, that helped a bit! That link points to a SimpleTech module at Amazon.com. Seeing how they explicitly say PC66, I went to the SimpleTech.com web site and looked around. This is interesting:

http://www.simpletech.com/parts/s256i3ed1qd.htm

A PC100 single bank SODIMM, however it's an ECC type. I couldn't find a non-ECC single bank described among their offerings but I still may try to contact them and see what they have.