Are there any physical descriptions between CAS2 and CAS3 memory?

Trazk

Junior Member
Dec 30, 2000
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I know the difference between them is access time, but how do I tell the difference between the two? Is there a program that will tell me which kind of memory I already have? Can you look visually at the chip and tell?

I'm in the market to buy a nice 256Mb of PC133, but I don't know if I want CAS2 or CAS3. I want it to work with my existing PC133 128mb chip.

Thanks.

 

TheBlondeOne

Member
Dec 29, 2000
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Cas2 or Cas3 is referring to the quality. If I'm not mistaken the Cas2 uses a 6 layer PCB and the Cas3 uses 4 layer.

You mak be able to tell the difference in the thickness of the board itself (but probably only if you have one of each in hand). You may be able to see the different layers.

Go thru the previous threads and you will find a lot of info on memory.
 

SaturnX

Diamond Member
Jul 16, 2000
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CAS 2 and 3 refer to the timing of the RAM chips, and not their quality (I've never heard of that). Well CAS2 is slightly faster than CAS3, and it will give you a very small performance increase, though if you want to check the current timing of your exisiting RAM, use the following program:

ctSPD Scroll down the download section.

Then simply buy RAM that is the same timing as your existing RAM, and you should be fine.

--Mark

 

peemo

Golden Member
Oct 17, 1999
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CAS Latency has nothing to do with PCB or the construction of an SDRAM module. It refers to the memory chip's access time. See this article and other at Ars Technica for a good description of RAM specs:

Ars Technica RAM Guide

If you look at the RAM module you will see manufacturers codes on the actual chips which identify the part and will allow you to look up specs. You may get a little info from Sisoft Sandra or better Motherboard Monitor which read the SPD info on the module and may tell you what teh speed of the memory is (e.g. PC100 or PC133) and the access timing ratings (e.g. 2-2-2 or 3-3-3).

Good luck.
 

Trazk

Junior Member
Dec 30, 2000
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Would I have any problem mixing the 2 kinds together if they are different? Would the faster memory take the speed of the slower?
 

peemo

Golden Member
Oct 17, 1999
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You may have no trouble mixing depending on how fast you're running your computer but the CAS3 memory will limit you so in effect you are buying CAS2 memory that you can't get the most out of.
 

dszd0g

Golden Member
Jun 14, 2000
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I could swear I hit that problem at one point when I was working on someone else's system. I don't remember the specs, but they had CAS 2 memory in the first slot and CAS 3 in the second slot and the BIOS detected the memory as CAS 2. Took me a while to figure out the cause of the lock ups, but forcing the BIOS to CAS 3 fixed the problem. Now I just wish I remembered what kind of mobo that was... But anyways, my point is if you mix CAS 2 and CAS 3 either make sure your BIOS detects and is set for CAS 3 or make sure your CAS 3 can run at CAS 2. A lot of good qualitiy CAS 3 can run perfectly stably at CAS 2.