CAS question

[lfe01]

I was reading on Kingston's website that there HyperX PC3200 DDR RAM's settings for running at 400MHz is: 2-2-2-6-1 (CAS Latency 2). What I can't find is the description for each number. I know that the numbers represent the number of clock cycles but on my motherboard (ASUS P4C800) when I try to make the memory changes, the last category will only set to either 4 or 8 instead of 1 like Kingston's website says. The memory settings order on my motherboard is like this:

DRAM CAS# Latency
DRAM RAS# Precharge
DRAM RAS# to CAS# Delay
DRAM Precharge Delay
DRAM Burst Length

Can anyone correlate the 2-2-2-6-1 to the above settings? Thanks.

Lonnie

 

[bum_jcrules]

I have a couple of questions for you first.

1. Asus does not formally support <A HREF="http://" target="_new">HyperX memory for use with the P4C800 and P4C800 Deluxe motherboards</A> nor does <A HREF="http://www.ec.kingston.com/ecom/configurator/modelsinfo.asp?SysID=+14686+&distributor=0&submit1=Search" target="_new">Kingston report that it does either</A>?

2. However if you use Kingston Value RAM; Did you know that you can only <A HREF="http://www.asus.com/products/mb/socket478/p4c800/overview.htm" target="_new">use 1GB of memory on that board if you use the KVR400X64 modules</A>? (Kingston states you can use up to 2GB but I would trust Asus over Kingston in regards to what a motherboard can support.)

3. Did you buy the modules already and are now looking to set the latency timings?

4. Did you know that the <A HREF="http://www.intel.com/design/chipsets/875P/index.htm?iid=ipp_browse+chpsts_875pdsk&" target="_new">Intel 875P</A> <b>ONLY</b> formally show support for <A HREF="http://www.intel.com/technology/memory/ddr/valid/dimm_results.htm" target="_new">certain memory modules</A>? Please notice the Kingston Value RAM is listed and the HyperX is not. I am not saying that it “Cannot” work with the Asus P4C800 motherboard, only that none of the companies state support. (Intel, Asus, and Kingston)




Okay with that being said; here are the settings. (T = Time in Cycles (K)= Kingston and (A) = Asus)


<b>DRAM CAS# Latency</b> (JEDEC symbol = <b>tCAS</b>)
(K) 2T
(A) 2.5T Default, 3T and 2T as optional settings



<b>DRAM RAS# Precharge</b> (JEDEC symbol = <b>tRP</b>)

(K) 1T
(A) 4T default, 3T and 2T as optional settings



<b>DRAM RAS# to CAS# Delay</b> (JEDEC symbol = <b>tRCD</b>)

(K) 2T
(A) 4T Default, 3T and 2T as optional settings



<b>DRAM Precharge Delay</b> (JEDEC symbol = <b>tRC</b> or also known as "Bank Cycle Time")
(K) 6T
(A) 8T



The <b>DRAM Burst Length</b> is not a latency setting. It alows for the length of a quadword burst. You can set your board to 4 quadwords and 8 quadwords. Set this to 8 quadwords.


The tRAS or the RAS latency setting would probably be the other 2T.


Now there are a few other things that you will want to modify on your board as well for specific memory settings. These are very important yet very much so overlooked by the Joe Overclocker let alone the average computer user.

The first is the <b>DRAM Idle Timer</b>. This should be set at 16T or 64T. This will be trial by error. Either should work but one will be better than the other. All of the other setting values should be disregarded.

The second is the <b>DRAM Refresh Mode</b>.
This should be set according to the maximum density that you are using. If you are going to use 1GB or more this should be set at 7.8 sec and if it is less then 1GB set it at 15.6 sec. JEDEC stipulates that it should be 64 sec but this will depend on the stability of the system. You can set it at any one of the three. The longer the better the system will performance will be. However if you start using larger capacities (More MB/GB) then you will <b>NEED</b> to refresh more often.


One thing I will say here at the end is that even if you set the motherboard settings to the maximum settings given by the memory manufacturer you might not be able to run at those timings. Go back and see the settings as they are stated on the <A HREF="http://www.intel.com/technology/memory/ddr/valid/dimm_results.htm" target="_new">Intel Memory Module System Validation Results</A>. Now they might work and they might not work.

Ill let Kingston speak for me and the others...

<A HREF="http://" target="_new">* Notice: All Kingston products are tested to meet our published specifications. Some motherboards or system configurations may not operate at the published HyperX memory speeds and timing settings. Kingston does not recommend that any user attempt to run their computers faster than the published speed. Overclocking or modifying your system timing may result in damage to computer components.</A>

I hope this gives you a good grasp on what you are looking to do.



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