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Using PC133 instead of PC100. Conflicts? 1

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RIBEYZE

Technical User
Jul 24, 2003
29
US
I have a home-built PII 400MHz with an ASUS P2b-f Motherboard and want to upgrade system memory. The ASUS calls for PC100 compliant DIMMs with the CPU Bus Frequency set at 100MHz. Does anyone know if using PC133 DIMMs with the CPU Bus Frequency set at 100MHz would cause problems?
 
Whenever you use faster memory than the maximum speed supported by your motherboard the memory will default to the motherboard's maximum speed. So in your case the system will see your memory as PC100 instead of pc 133. There should be no problems in that, just that you may have overspend money.
 
There are many problems between those two memory standards that motherboards may not agree with. If you can, stick with PC100 memory, just in case. I've even got a KT133 athlon board that does not care for PC133 memory, I have to use PC100 so the machine runs stable (w/ 100fsb athlon of course).
 
Despite what "should" happen, as Dakota has said, newer PC133 modules often don't work on motherboards that were designed initially for PC100.
Partly to do with the density of the modules and also to the differant specifications of the chips themselves.
One thing you can generally count on though, if you can get hold of second hand sticks of PC133 that were made around the change between PC100/133 they nearly always work fine.
If you have a local PC supplier that is flexible enough for you to try a couple of differant brands?? go for double sided modules that are populated more densely (more chips) they are more likely to work.
The other common problem is some newer types only reporting half there size.
Martin

Replying helps further our knowledge, without comment leaves us wondering.
 
[tt]Hi paparazi,

quoting you, "The other common problem is some newer types only reporting half there size" what may cause that problem? I have a Kingston PC2100 512MB and there was this one time my ECS K7S5A mobo reported only 256MB. Dont know what I did ( I was a little frantic, did many things at one go, I know that aint good but heck it did the job anyway) but I got it back to reading 512MB. Just curious, under what circumstances would a RAM stick be seen at only half it's size?
 
Yeah, I had the same problem on a Gigabyte GA-7DX when it would only read 128mb when adding a 256mb stick (someone told me the boards were particularly fussy about ram. I fixed it in the end with 1gb of Crucial so never did find a solution/cause!
 
Well, thanks for the replies. I guess it all boils down to try it and see what happens. The only reason I'm inclined to go this way is price. Tiger Direct has a smokin' deal on Ultra 128MB PC133 SDRAM.


It would cost much more to purchase the PC100. I guess I could buy a single 128MB stick and cut the loss if it doesn't work out. I could probably re-sell it for more than I paid if the rebate works out.
 
As it turns out only half of the installed 133 RAM is recognized.
 
That's another problem,definitely not caused by the frequency...
 
RIBEYZE
Wow! thought this post was long gone.
Unfortunately, as you have found out, newer PC133 modules often either only recognise half there capacity or don't work at all.
If you are still determined to get some memory that works fully then order online from Crucial, they gaurantee 100% compatibility when supplying.
Martin


Start by questioning and soon you will be anwering.
So please take but remember to return and give when you can.
 
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