Correct 256 RAM memory stick for 600e *6KB PIC*

[Olde Man]

I have a 600e (Type 2646-8BU) laptop with two 128 sticks in it.

Should a 256 stick chance by, what kind can I use?

I have reviewed the literature and ended up confused mainly because nobody talks about the 2646, only the 2645. I assume there was some good reason IBM changed the type #. . .

[rkawakami]

2645 and 2646 systems are basically the same; I believe the major differences were in the type of warranty service they received or OS that was provided. The 600 series systems required the use of what is normally called "low density" memory modules. 256MB modules can be used however they must have 16 individual memory chips on the board; 8 per side. This is what identifies "low density" from "high density". There are modules which violate this rule but they are rare. Follow this table and you should be fine:

128MB Low Density
total of 8 memory chips

256MB Low Density
total of 16 memory chips

A common part number available from Micron is MT16LSDF3264. The 16 denotes 16 parts on the board (i.e., low density); the 3264 describes a 256MB module. If you see a Micron MT8LSDF3264 or MT8LSDT3264, then that's a high density module (8 chips on the board) and it will not work in the 600 series systems.

[pkiff]

The 16 denotes 16 parts on the board (i.e., low density); the 3264 describes a 256MB module[....]

Still learning things about old memory modules from you, Ray, even after having covered this ground many times now! Thanks for the details, Phil.

[jdrou]

Make sure you have the last BIOS. I believe support for the 256MB modules was only added in a BIOS update.

[Olde Man]

I have the BIOS update which is what attracted my attention.

Thanks for the info. I shall now retreat to my lair and see if I can induce one to come by.

[rkawakami]

Still learning things about old memory modules....<snip>

Here's the relevant file from Micron's documentation system: http://download.micron.com/pdf/numberin ... rammod.pdf

The third page lists old DDR/SDR modules. For the MT16LSDF3264HG module, "MT" identifies it as Micron (Technology). The "16" is for the number of memory components. "L" is for 3.3V parts, essentially SDRAM. The "SDF" is SDRAM memory in FBGA packages. The "3264" is 32M addresses by 64 bits or a total of 256MB. The "H" following the 64 is for a 144 pin SODIMM and the "G" is for commercial temperature grade (what is normally available in the marketplace). The remaining letters/numbers signify the speed rating of the module and the revision. The Micron documentation I referenced above does not list all of the older (read: slower SDRAM) memories. Since the 600E can accept modules as slow as 66Mhz, there's really no need to be concerned about the speed rating as there should be no modules slower than that. What are typically seen now are "-10" (PC100 or 100Mhz) or "-13" (PC133 or 133Mhz) parts. However, I would still recommend the 100 or 133Mhz modules over any 66Mhz module simply because they probably cheaper, more readily available and you can always use them in a 600X (and some other legacy) systems.

[Neil]

Thank you guys for bringing this topic up. I have a 600E around here that was getting some use next to the cash register at the store. It also had the published maximum RAM, 288MB. But, I have this machine at the house at the moment, with a couple 256MB sticks of PC100 RAM in the desk drawer that had been pulled out of a now sold 600X. So, I thought "I'll just try this", and stuck both sticks in the 600E. I thought I had tried this once before and couldn't get it to boot, but the ThinkPad splash screen read 556480, and now that I've booted up Linux Mint (Gnome) it's showing 528.4MB of RAM. Shouldn't that be 512+32=544-2.5 (graphics)=541.5? So, what did Mint do with my other 13MB RAM?

[rkawakami]

Based on what my 600X, with 576MB of memory shows, your figure of 556480 is correct. Here's a screen shot of said 600X:



This is how the math goes: 2 x 256MB + 64MB = 576MB. MB=1024, not 1000 so 576 x 1024 = 589824. Subtract out the 589248 that shows on the splash screen, leaves 576 (KB). With your 600E, total memory is 544MB. 544 x 1024 = 557056. Subtract 576 and you get 556480. I believe the 576KB has to do with the "base" or conventional memory, as opposed to extended or expanded memory. Base memory is 640KB so that still leaves 64KB unaccounted for. That could be a memory page of 64KB.

I don't believe any of the system memory in the 600 series systems are used for the video display. The GPU has its own dedicated memory.

ref: http://en.wikipedia.org/wiki/Conventional_memory