Incompatible RAM?

Question

I bought a computer made from old parts from an electronics recycling center. It came with 256MB of RAM. Two sticks, one that says pc100 and the other pc133.

I tried replacing these sticks with some other ones I had. Unlike the sticks that came with the computer, which fit into black slots and had two notches in each chip, the memory sticks I put in myself each had only one notch and fit into the  blue slots. Both were 256MB, one says "Corsair VC256MB400" and the other says "Mushkin 256MB PC2100".

First of all, the computer wouldn't boot if I had both types of memory sticks in the motherboard (which is a socket a, I believe, as the processor is a celeron); I could only use the one-notch sticks or the two-notch sticks but not both.

Also, even though my computer has twice as much memory now (512MB as opposed to 256), it doesn't seem to run any faster, and frequently has to enlarge the virtual memory allotment.

Can anyone bring me up to speed on this? Any online resources for info?

aztut · Accepted Answer

The 2-notch Ram is SDRAM and the 1-notch Ram is DDR.  One of the DDR is a 400Mhz stick and the other is a 266Mhz stick.  Also, a Socket A is an AMD pin configuration(Athlon or Duron) not Intel Celeron.  Since I don't know what mobo it is, I can't tell you if there are settings in the Bios that need to be set, although it should be set to Auto for RAM speed settings.  512MB of RAM is plenty for XP unless your gaming or doing alot of picture and video editing.

Another computer builder · Answer

The newer sticks will only be faster if you have the settings in the BIOS set right. When your computer boots, you may need to hit del to get to it. There should be settings for the RAM in there. If the slower of the 2 sticks is pc2100, then you would want to set the RAM and FSB to 133. Don't worry, it's Double Data Rate (DDR) memory, so it will act as if it is operating at 266, which is considerably faster than pc100 or 133.

Also, if you have a total of 512 or RAM and your computer is using virtual memory, then you probably have virus, adware, or just too much running in the background. 512 is enough for XP and win98 to run fine if there isn't a virus or something running that is consuming lots of memory.

William V · Answer

First, it's not unusual for a motherboard to require one type of memory or another. Choose the type with most capacity.
Next, 512mb is not much RAM for XP. It's just barely enough for Windows 98 but it should be enough. I expect you're truing to run XP--you need twice as much RAM (at least). Virual memory messages mean that the system is having to expand the swap file (not good) as swapping slows down the system (a lot). Swapping occurs when programs and data dont' fit into memory.

hth

Andy T · Answer

For RAM, PC100 and PC133 are SDR RAM that is physically incompatible to the DDR you try to stick in, the two grades of SDR cannot operate smoothly together same goes to DDR. But outright unable to turn on probably mean one of them is already faulty.

What kind of two computers you are comparing together? If one runs Win 95 the other is Win XP they are way off to be compared.

Frank N · Answer

If you have a motherboard that supports both PC RAM and DDRAM, you must use one or the other type, but not both at the same time.
DDR is double data rate, (faster than PC100 - 133)

spike · Answer

the pc100 and 133 are compatible.but the corsair and pc2100 are DDR ram and are NOT compatible to the pc100 or pc133....your got to 1GB of RAM for XP to work rigth..

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Incompatible RAM?

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