Cas?

[bodezafa]

Dont know much about memory so Im going to ask this. What is this CAS you all are talking about?

 

[Pinky]

Defined (forgot what the acronym stands for, something Strobe):

It is the speed at which the PC addresses the memory. The slower the number, the faster the addressing. Hence, CAS2 is faster than CAS3, and tends to be more expensive amd generally better quality.

 

[bdf24]

Generally though, most name brand ram even labled as cas 3 or cas 2.5 for DDR will do cas 2 with no trouble at all. Depending on how high of a FSB you are running of course.
I had some corsair PC 133 cas 3 that ran 100% stable at a FSB of 140 @ cas 2.

 

[lennytiger]

i have a setting in my bios for memory either cas2 or cas3, I think my memory is cas3 so i se it to that but it works just as well on cas2.

 

[bodezafa]

so how does it relate to the FSB?
if you up the FSB and it is unstable would lowering the cas be part of the trouble shouting?

 

[bdf24]

Well normaly running cas 3 ram at cas 2 will work fine. But if you start jacking the FSB up there you may have to lower the ram back to cas 3 to get the pc stable. Where as cas 2 ram rated at the same speed will more then likely take the higer FSB without having to lower it to cas 3.

 

[JigPu]

CAS = Coloum (me... need... spellcheck....) Address Strobe
(There is also RAS... Row Address Strobe. No idea what it is used for though...)

It is how many cycles the system "strobes" the ram in. The lower the number, the faster it is strobed, and thus the faster it shoves out data. When you bring up the FSB, your ram timings increase too.

For example 133Mhz RAM at CAS3. It is strobed 133/3 million times per second. When you bring up the CAS to 2, it gets strobed 133/2 million times per second. When you raise the FSB up high enough, the RAM can't be strobed that fast. It wasn't designed to work that fast, so either you have to slow down the FSB, or increase the CAS value. If it dosen't run too well at 140/2, then it should run better at 140/3 because the RAM isn't being strobed as fast.

I personally think that having the lowest CAS possible with the highest FSB produces the best result, rather than bringing up the FSB and increasing the CAS number by one.

All this is based off my search for BIOS settings on my P-90... If something major has changed, please tell me. I got only old machines, so I don't know as much about "new" technolagy. Didn't they make RAM and FSB settings independent of each other?
JigPu

 

[Robbie]

well if I remember correctly from school. What the computer is doing is Refreashing the Ram. Basicly the cells in the Ram hold a charge for only soooo long, so the charge has to be refreashed. Think of it like small little batteries that lose there charge after so long, so they have to be rechareged.

Remember the computer does this like thousands of times per second. (depending on the Mhz of the cpu) humm well maybe not thousands?!?!


Hope this helps.

Refreash on

Rob

 

[bodezafa]

Thanx that helps alot!