It must be some of that fuzzy math.

My server has 128MB of PC100 SDRAM. Today, I bought a 256MB stick of PC133 SDRAM. I put it in my server’s second RAM slot. When the system booted up, it reported only 160MB of RAM in total. Upon booting into Linux, free -m and dmesg confirmed this tally. I took out the PC100 and tried to boot with only the new RAM. I got only a beep code, indicating a parity problem. I reverted to using only the PC100, and my server booted happily, back to having 128MB of RAM.

A bad stick of RAM? Or am I doing something dumb?

Published by Waldo Jaquith

Waldo Jaquith (JAKE-with) is an open government technologist who lives near Char­lottes­­ville, VA, USA. more »

4 replies on “It must be some of that fuzzy math.”

  1. It’s gotta be bad, unless I’m also just not thinking about something. RAM these days is keyed so you can’t put it in wrong. Check your BIOS settings and make sure there’s nothing insane going on, a setting like “Disable extra RAM because we’re idiots.” Is it possible that older motherboards won’t support PC133, so that’s the best guess I have. A quick Google search turns up PC100-PC133 incompatibilities, but that doesn’t explain why the PC133 didn’t work just by itself.

  2. Upon further discussion with my techie cohorts who have done hardware work more recently than I, the likely culprit is that your MB doesn’t like PC133. Check up on your motherboard docs on the net and see if it allows PC133.

  3. I have independently come to the same conclusion as your techie cohorts, Chris. I called my local screwdriver shop, from whom I bought the RAM, and they say that the symptoms are perfectly consistent with wrong-speed RAM. They’ve ordered a 256MB SIMM of PC100, which they’ll have in on Tuesday.

    My server — named Johnny, incidentally — thanks you. :)

  4. The other reasonably plausible option is a motherboard limit on the amount of RAM it can recognize.

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