3 GB RAM limit?

Eric Elliott · 01-26-2008, 10:43 PM

Want to use 4 GB RAM in Thinkpad Z61m, 9450A38. Book says it will only use 3 GB but more RAM is OK. Question is, is 3 GB a Windiz limit or a limtation of Intel 945 chip set?

Question 2, is PC2-6400 memory good in computer intended for PC2-5300 RAM?

Complete info for my Thinkpad is in LQ HCL.

No, Kubuntu does not need 4 GB. Intent is to run Kubuntu, VirtualBox, Windiz XP, CoPilot, VMSpc & several Linux programs concurrently.

lazlow · 01-26-2008, 10:48 PM

It is probably the 32bit limit. If that is the case I hear about 3.1GB being what shows up. If you can run 64-bit that issue goes away.

Faster memory in a slower machine seldom causes any issues but it will probably only run at the slower speed.

MyHeartPumpsFreon · 01-27-2008, 08:25 PM

Just reiterating what Laz said... if you install a 64-bit version of your favorite Linux flavor, the problem will go away. However, depending on your setup, you may not be able to install a 64-bit version.

I looked up the laptop and one of the available processors is a Celeron... which is NOT 64-bit. They have Core2Duo's available and that is 64-bit. So, you just may be stuck with the 3GB limit.

In my experience, Linux has excellent memory management. With just 512MB running Fedora 8, it never went into the SWAP ONCE. I upped to 1GB just in case, but it still runs just as well as it did with 512MB.

Regards,

Brandon

H_TeXMeX_H · 01-28-2008, 02:41 AM

You don't even need to run a 64-bit kernel to get access to more than 4 GB RAM. You could just turn on hugemem support, which support up to 64 GB RAM. However, it could be a hardware limitation such that this will not work. I say try it anyway. Not sure if kubuntu has a pre-built kernel that supports it, look around, if not try compiling one (not from scratch, just use the config kubuntu uses but enable 64 GB RAM support).

EDIT: I'm assuming you have the thinkpad with a Core Duo, in which case you must compile the kernel specifically for it in order for this trick to work.

farslayer · 01-28-2008, 09:05 AM

Probably a BIOS limitation of the hardware..

what does lshw tell you ?

Code:

it-etch:/# lshw -C memory
  *-firmware
       description: BIOS
       vendor: Dell Inc.
       physical id: 0
       version: 1.1.2 (12/04/2006)
       size: 64KB
       capacity: 448KB
       capabilities: pci pnp apm upgrade shadowing cdboot bootselect edd int13floppytoshiba int5printscreen int9keyboard int14serial int17printer acpi usb ls120boot biosbootspecification netboot
  *-memory
       description: System Memory
       physical id: 1000
       slot: System board or motherboard
       size: 1GB
       capacity: 2GB
     *-bank:0
          description: DIMM DDR Synchronous 533 MHz (1.9 ns)
          product: KHU006-QIA
          vendor: 7F98000000000000
          physical id: 0
          serial: A036F583
          slot: DIMM_1
          size: 1GB
          width: 64 bits
          clock: 533MHz (1.9ns)
     *-bank:1
          description: DIMM DDR Synchronous 533 MHz (1.9 ns) [empty]
          vendor: FFFFFFFFFFFFFFFF
          physical id: 1
          serial: FFFFFFFF
          slot: DIMM_3
          width: 64 bits
          clock: 533MHz (1.9ns)

This particular system which was purchased new last February, will only support a total of 2 GB of RAM. 1 - 1 GB stick in each slot. I haven't got my grubby little fingers on any 2 GB sticks yet to see what happens, but since the BIOS says no, I have a feeling it's just not going to work.

H_TeXMeX_H · 01-28-2008, 02:33 PM

I agree that if there is a limit in the BIOS, Linux cannot bypass it (AFAIK).

But when I run 'lshw' it doesn't list the capacity ... strange.

Code:

     *-memory
          description: System Memory
          physical id: a
          slot: System board or motherboard
          size: 1GiB
        *-bank:0
             description: SODIMM DDR 133 MHz (7.5 ns)
             product: N/A
             vendor: N/A
             physical id: 0
             serial: N/A
             slot: SODIMM1
             size: 512MiB
             width: 32 bits
             clock: 133MHz (7.5ns)
        *-bank:1
             description: SODIMM DDR 133 MHz (7.5 ns)
             product: N/A
             vendor: N/A
             physical id: 1
             serial: N/A
             slot: SODIMM2
             size: 512MiB
             width: 32 bits
             clock: 133MHz (7.5ns)
     *-pci

Just so you know 1 GiB is the maximum capacity, even tho it isn't listed here.

lazlow · 01-28-2008, 02:57 PM

TexMex

In your case I THINK it is showing you. If you compare your "width" it is showing 32bits, versus Farslayer's width showing at 64bit.

farslayer · 01-28-2008, 03:39 PM

if the "width" were the only limiting factor, mine should support far more than 2 GB.

I'm not sure what exactly determines the max RAM a system board can take, I'm sure it's probably a combination of the width of the memory bus, the chipset used on the motherboard, and any BIOS limitations set by the manufacturer..

the detail level of that command certainly does vary between systems, the old 1 Ghz dell I had on my desk a while back had a limitation of 1 GB plainly listed in the output of lshw. I'll have to look at the other whitebox systems I've built to see how their output compares..

lazlow · 01-28-2008, 03:42 PM

I guess I was saying that the bios supports 64bit addressing based on width. Not the amount of ram it was supporting.