PC 133 with PC 100 Memory

Microsoft Windows xp professional editio...
September 22, 2009 at 12:59:34
Specs: Windows XP, Pentium 3 450 MHz
One of my systems is an old Gateway 450 system with only 96 MB of PC 100 RAM. I got Windows XP installed on it and I bought 256 MB of PC 100 RAM. Now, when I installed it, the PC detects it perfectly but when Windows XP boots up, it kept rebooting. I finally had to install the memory one by one and then it stopped rebooting. I logged in, installed CPU-Z and it detected that the 256 MB stick is actually PC 133 where there other sticks are only PC 100! Maybe thats why it kept rebooting for no reason. However the system was stable so far but the moment i logged off and logged back in, it rebooted again.

Some websites said that PC 133 is backwards compatible, and it apprears to be, but Windows XP kept rebooting the system with a BSOD occasionally.

Now, do I reinstall Windows XP or do I return the RAM to the owner and tell him he gave me the wrong RAM?

What do I do?

See More: PC 133 with PC 100 Memory

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September 22, 2009 at 13:08:18
Try any linux, Vista, Windows 7 disk for MEMTEST.

Run it and see what is up.

Might look at bios also. Might have to accept the new settings. Might have to force the speed to 100 if possible.

Playing to the angels
Les Paul (1915-2009)

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September 22, 2009 at 13:08:21
Give us the serial number of your Gateway so we can go here and get some details about your machine.


And yes, the memory may not be compatible.

You may need to do a repair install of XP but, I don't think it should be necessary with just a memory upgrade.


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September 22, 2009 at 13:12:45
Memory has different densities as well as single sided and double sided, some motherboards except all, some one type and not another. Also PC133 can be backward compatable, depends on Motherboard.

Is this you PC ?


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Related Solutions

September 22, 2009 at 13:14:50
You may be installing the PC133 in the first memory slot. If you do that the auto settings on the memory controller will try to run all the RAM at 133 speeds, which your PC100 probably won't do.

Best to boot into the BIOS screens and MANUALLY set the RAM to run at 100 settings.

If no manual settings are available then install the PC100 in the first slot.

In the end you may not be able to get the new RAM to work. OEM vendors tweak their memory controller to work with certain RAM specs and the PC133 may not meet those specs.

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September 22, 2009 at 13:34:51
In addition to OtH's remarks, if you do get it to work, it can be painfully slow.


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September 22, 2009 at 14:08:27
IMO, that system isn't XP-worthy. Win2K would be a better choice, or experiment with Linux.

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September 22, 2009 at 14:47:32
Thanks for the replies. SkipCox, the computer runs fine speedwise, just the rebooting in Windows XP is an issue with a BSOD. That is why I asked weather reinstalling Windows would solve this problem. OtheHill, I put the PC 100 64 MB Memory before the PC 133 256 MB and I it turned on fine, I haven't tested it yet fully though. Should I instead remove ALL 96 MB PC 100 and just use 256 PC 133 instead if thats the case OtheHill?

Also SkipCox, I though you knew what Gateway I am talking about since there is only ONE Pentium 3 450 MHz system. This is the serial:


This is what it looks like:


I would be using Windows 2000 on this one, but right now, some computers do not work and I need this computer to work for the time being with Windows XP. Once my other computers work, I will be putting Windows 2000 and this one will be spare.

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September 22, 2009 at 20:05:17

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September 22, 2009 at 21:52:29
The memory controller is satisfied when it sees a PC100 module in the first slot.

If the computer is starting up and running fine now just add one module at a time and retry. Don't remove any working RAM.

Win2000 & WinXP should both be able to run the same programs. So, anything requiring WinXP should work fine with Win2000.

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September 23, 2009 at 01:18:08
OtheHill, the system crashes when I install this memory. It works, but the OS goes into BSOD. Its PC 133. All other RAM which is PC 100 doesn't do this.

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September 23, 2009 at 06:24:52
If the PC133 crashes the computer then the memory controller either can't deal with mixed different RAM specs or can't downgrade the PC133 to 100 speeds.

True PC100 is probably harder to find than PC133. So, I suggest you try inserting ONLY the 1 stick of PC133 to see if the computer boots and is stable. If it is then hunt down addition PC133 with the same or close specs as the 1 stick to up the total count.

Alternatively, crucial.com guarantees the RAM they recommend to work. You can use their online configurator to find out exactly what RAM you can use and how much of it.

Your board may actually only support PC66 and even the 100 is being clocked down.

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September 23, 2009 at 08:55:20
This is why I asked for the serial number...


Read every word. Appears 3 128Mb chips is max for this board and match memory speed to processor speed.

Edit: Your machine specs...



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September 23, 2009 at 16:59:37
According to Skip's link, your system doesn't support 256MB sticks of RAM.

"the computer runs fine speedwise"

Obviously you & I (& probably the others involved in this thread) differ on what is considered acceptable speedwise. Did you ever use a system that has say, 1GB RAM? If you have, you should know how horrible 96MB is. 384MB (3 x 128MB) would be an improvement but IMO, still not worthy of XP. I highly suggest you wipe the HDD & install Win2K. If you insist on running XP, buy some decent RAM of the right capacity & type...in other words, 128MB PC100.

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September 28, 2009 at 16:17:46
Sorry for taking too long to reply. I decided get 3 128 MB sticks and put the 256 MB PC 133 on another computer and it runs fine now. I felt that I could upgrade to a 20 GB Hard Drive, so I upgraded and having another problem with the machine:


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September 29, 2009 at 08:07:28
I wouldn't spend any money for that computer.
It's simply to old and, if I'm right, it has 450 MHz CPU.
Even if you get windows xp installed and running properly, it isn't funny to work with it.

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