DDR Cas Latency Problem

[theSlex]

Hello,

I upgraded my desktop after returning from Basic Training two years ago. I purchased a gig (two 512 sticks) of Corsair RAM (DDR 400 PC3200).

Link:

http://www.newegg.com/Product/Product.asp?Item=N82E16820145450

My hard drive crapped out on me recently, so I thought I'd toss in another gig of RAM while I was ordering. I bought another gig of Corsair DDR 400 PC3200 RAM:

Link:

http://www.newegg.com/product/product.asp?item=N82E16820145440

Apparently the old RAM has a Cas Latency of 2, and the new stuff has a Cas Latency of 2.5. I wasn't aware that this was a problem (the rest of the specs seemed in line).

Is there anything I can tweak to allow my system to run these four sticks in harmony? I've already gone past my return date on the new RAM. Any help is much appreciated.

 

[cdogg]

We need to know what motherboard you have and whether or not you are trying to run it in dual-channel. Dual-channel is more sensitive to memory timings like CAS Latency as opposed to single-channel mode, so that may be what you're trying to do. It shouldn't be an issue otherwise.

It would also help to know what CPU you have too...

~cdogg
"Insanity: doing the same thing over and over again and expecting different results." - Einstein
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[theSlex]

Thanks for the quick reply!

My motherboard is an Asus A8N-SLI Deluxe. I can't seem to find its specs anymore, but Asus produces an A8N32-SLI Deluxe (

http://usa.asus.com/products.aspx?l1=3&l2=15&l3=226&l4=0&model=744&modelmenu=2

) which I'd imagine has to be similar.

My processor is an AMD Athlon 64 3000+ Winchester 1.8GHz. Once again, I can't seem to track down it's specs.

As for running dual channel, I don't know the difference between running single channel and dual, so that very well might be the problem.

I tried placing the four sticks in a variety of locations, OLD in DIMM 1 and 2, NEW in 3 and 4; OLD in 1 and 3, NEW in 2 and 4. System gave an error during the initial boot each time.

How would I go about enabling single channel? Thanks again.

 

[cdogg]

If you look at section 2-12 in your motherboard's manual, it will show you the memory configurations that are compatible. It even has a list of known vendors and memory models that have been tested and known to work.

It looks like you want your original gig of memory in DIMM slots A1 and B1. Then install the new memory you just bought in slots A2 and B2. Even though you have Channel A and Channel B, the first slot in each channel works directly with the first slot in the other channel, which is why you want those to match. The same is true for the second slot in each channel.

If that doesn't work still, then either the CAS latency is the problem or you have "double-sided x16" chips that the manual says won't work on this board. I couldn't find a way to disable dual-channel in the manual (I suppose it only relies on the way you install the memory).

It also says this:

Always install DIMMs with the same CAS latency. For optimum compatibility, it is recommended that you obtain memory modules from the same vendor. Refer to the memory Qualified Vendors List on the next page for details.

~cdogg
"Insanity: doing the same thing over and over again and expecting different results." - Einstein
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[kmcferrin]

Don't know what specific problems you're having with CAS latency, but most motherboards give you the ability to set memory timings manually. If yours does then you should be able to set them to 2.5 across the board (slower than 2.0, but the 2.0 memory should be able to run slower with no issues) and that would take care of it.

 

[theSlex]

I've got the original gig in A1 and B1, the new stuff in A2 and B2.

The system boots, but only recognizes a gig of RAM. Strangely enough, according to CPU-Z the RAM in A2 and B2 (the new stuff) is being used, as opposed to the original stuff in A1 and B1. The motherboard manual says to place RAM in A1 and B1 if only running two sticks.

I've tried placing the CAS latency at 2, 2.5 and 3 from the BIOS settings but each time the system displayed 1 gig of memory when booting.

Also of note, CPU-Z's Memory tab says the system has 2 gigs of RAM, but the system itself doesn't seem to recognize that.

 

[Freestone]

Maybe the XMS memory is just too fast for the Value Select.

Your higher performance memory (TWINX1024-3200C2PT) has timings of 2-3-3-6 (

http://www.corsair.com/products/xms.aspx)

whereas the Value Select memory (VS1GBKIT400) has 3-3-3-8 (

http://www.corsair.com/products/value_select.aspx).

If your BIOS lets you, adjust the CAS to 3 and the fourth timing (tRAS ?) to 8.

 

[cdogg]

Quote: "[blue]The motherboard manual says to place RAM in A1 and B1 if only running two sticks.[/blue]"

That doesn't matter here because you're using all 4 slots. However, that part is important because it shows how the slots run in tandem with each other when dual-channel is involved. A1 goes to B1 and A2 goes to B2, which tells you how to match up the sticks.

I would try Freestone's suggestion on changing the timings for the TWINX1024 DIMMs. However, Freestone says the Value Select memory is rated at 3-3-3-8. That's a little off. Looking at the chart in that link, the VS1GBKIT400 is rated at 2.5-3-3-8. So change the CAS to 2.5 and the RAS to 8.

If that doesn't work, it would be best just to leave the older TWINX1024 in the system and sell off the value sticks you just bought. Even if you got them to work, I doubt you'd notice much difference in overall performance unless you're running Windows Vista.

~cdogg
"Insanity: doing the same thing over and over again and expecting different results." - Einstein
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[Freestone]

cdogg - heh, good catch. Somewhere between listening to the 4-yr old, talking to the wife, and copying the VS1GBKIT400 specs (or so I thought) that pesking 2.5 CAS got changed to 3. Thanks for posting the correction.

 

[djsrc]

I just upgraded my humble 512 mb of CAS 3 DDR double sticks on my Dell 8300, adding another two sticks of 256 mb each, for a total of 1 gig (cost me a whopping $36 including shipping), and went loony tunes over the not rare dual definitions of terms in comp tech, in which something like CAS 3 and Class 3, are in fact, the same meaning.

That may be obvious to many of you, but if it's the first time you are trying to order additional certain parts for your computer, it is quite confusing.

Anyway, when I finally looked at the BRAND of RAM that I had originally (SAMSUNG), and then went to GOOGLE to research it, I was able to figure that out.

However, at the time I ordered the RAM sticks, there were no SAMSUNG 256 mb sticks in stock from NEWEGG, so I ordered WINTEC, and they seem to work just fine.

BTW, I can't help but notice how much faster programs load and run, even just bumping to 1 gig from 512 mb. Someday (secret strategy), as DDR SDRAM becomes more obsolete and therefore cheaper, I will bump up to the max four sticks of 1 gig each.

Much to my surprise, WIKIPEDIA states that DDR SDRAM is superior, in fact, to DDR2 RAM, at least according to however wrote the article, but that for reasons I don't understand, DDR2 is faster, whatever that means.

Oh well, I'm not going to worry about it because I understand that very soon, within a few years, memory is going to be reduced to the ATOMIC level, as in protons and electrons, and then all of this crazy stuff will just be history, so to speak.

It's a good thing I took chemistry in HS!

D

 

[kmcferrin]

and went loony tunes over the not rare dual definitions of terms in comp tech, in which something like CAS 3 and Class 3, are in fact, the same meaning.

I've never heard anyone refer to "class 3 memory". But when talking about memory, "CAS" stands for Column Access Strobe, and "CAS 3" refers to the timing of the CAS. Lower numbers are faster, resulting in lower lantecy.

Someday (secret strategy), as DDR SDRAM becomes more obsolete and therefore cheaper, I will bump up to the max four sticks of 1 gig each.

The time may be now. It's fairly obsolete now, but if you wait to long you run the risk of it being so obsolete that it's either a) not available or b) harder to find, and therefore more expensive. Memory prices follow the bathtub curve usually (as do most computer components).

Much to my surprise, WIKIPEDIA states that DDR SDRAM is superior, in fact, to DDR2 RAM, at least according to however wrote the article, but that for reasons I don't understand, DDR2 is faster, whatever that means.

DDR2 has more bandwidth (can transmit more data per cycle), but it is a higher latency memory technology. However, newer DDR memory is being produced at lower latencies, so this may not remain the case for long. Also, overall latency isn't just related to the latency between the memory controller and the RAM, but it is also affected by latency between the CPU and memory controller. CPUs that use an integrated memory controller (Athlon 64, X2, FX) have much lower CPU to memory controller latency, resulting in an overall reduction in latency.

 

[cdogg]

Yeah, in reference to the comment about DDR being superior to DDR2, that really depends what you're looking at. In terms of latency, that's true for the most part. If you compare DDR1 and DDR2 running at the same speed, DDR1 will kill it every time. However, DDR2 easily has bandwidth capabilities far beyond DDR1's reach. When you start talking about speeds like 1066MHz and higher, DDR2 is the one to go with.

So because the potential of DDR1 was limited, DDR2 stepped in to take performance to the next level.

~cdogg
"Insanity: doing the same thing over and over again and expecting different results." - Einstein
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[kmcferrin]

Good points, I had forgotten about why we went to DDR2 in the first place.

 

[djsrc]

I fully understand the bathtub curve principle from having just shopped for an AGP 8X video card, and finding that they are more expensive than the later generation PCI-E 16X models using the same chipsets.

Very annoying.

Anyhow, PC 3200 400 mhz DDR SDRAM , will probably be available USED on Craigslist & Ebay, for the next 1,000 years.

As far as the CAS vs. CLASS, or CL designations of RAM:

1-When I looked at the two Samsung 256 mb sticks that are in my Dell 8300, it actually says CLASS 3, on the sticks themselves.

And to even further confuse me, here are two links to RAM, that designate PC 3200 400mhz RAM as CL 3.

Take a look for yourself:

2-

http://www.pcmemorystore.com/Standard_DIMMs-PC3200_(400MHz)_DDR-184^pin_non^ECC-ram.htm

(This link has to be copied and pasted in its entirety into your browser, for whatever reason. The Nextag link seems to work okay. Sorry.)

and

3-

http://www.nextag.com/All--a-memory...2z5---html?nxtg=3f520a1c0516-702784E2C418C6BE

(under the NEXTAG logo on the top left, it shows CL 3, as a class of RAM)

Now, on at least one of those sites, or some other one from a GOOGLE search, which of course I cannot seem to locate at the moment, it then shows the Samsung RAM type as having a CAS 3 latency.

Anyway, the two new sticks of WINTEC 256 mb 400 mhz RAM show up in my BIOS, and appear to be working just fine.

If I am under some misconception as to CAS 3 and CLASS 3, or CL 3 RAM being the same thing, please illuminate me, ASAP.

Otherwise that RAM is non-ECC, as opposed to ECC, which I found out is an error checking feature, I think?

(Crawls back under rock)

 

[kmcferrin]

CL3 just means CAS Latency 3, or Column Access Strobe Latency 3. Instead of using the words "CAS Latency," it is often shortened to "CAS". But when someone refers to CAS 3 memory they mean memory with a CAS latency of 3 cycles.

I've never heard of anyone refer to it as "Class 3", unless someone saw "CL" and heard people say "CAS" and assumed that they were saying "class

 

[djsrc]

I'm quite sure you are correct in that, "kmcferrin".

However, it doesn't change the fact that it actually says:

"CLASS 3" like that exactly on the bottom of both 256 mb sticks (not the chips) of my Dell issued SAMSUNG system RAM, not "CAS 3" or "CL 3".

I assume that's the way the South Koreans have interpreted it, or translated it, or whatever.

In the long run, it didn't make it any easier for me to figure out what that meant, since I have had to deal with three different ways of listing CL 3 latency on RAM.

I'm sure at this point, that the translation thing is what's going on there.

All the best,

DJSRC

 

[cdogg]

Where I work, we have over 10 brands of DDR and DDR2 that I work with everyday. Even the Samsung brand uses CL when they rate latency. I have two PC2100 sticks right here from Samsung that say CL 2.5.

I also did a search on "class 3" and "ddr" without turning up any hits. That's the first time I've heard of that as well. Maybe it stands for something else, like Kingston's Value Select terminology? I'm just curious here, but is it on a white label or is it engraved/printed on the DIMM?

~cdogg
"Insanity: doing the same thing over and over again and expecting different results." - Einstein
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[djsrc]

Well, the last time I looked, which was before I ordered the WINTEC RAM, just to be sure because of the confusion thing, was about three weeks ago.

As far as I recall, (which is not saying much), it is printed right on the DIMM, not on a piece of attached paper.

I would be happy to pull off all of the wires and connectors to my tower, and open up the sucker, and pull out the DIMM, shoot it at 640X480, and then upload the pic, but I didn't think that was necessarily possible on this Forum.

Is that possible?

I would be happy to do that if you like.

Otherwise, I could send it to a specific E-Mail address, if supplied with one, from you or someone else, to verify my observation.

Either way, tomorrow morning I will open up the case and double check it, but I am pretty sure that I am 100% correct on that.

It's just something of a pain to have to disconnect everything, and then reconnect it all, when one is as latently lazy as I am, so to speak...

Anyway, let me know.

BTW, and now that I think about it, when I GOOGLED the Samsung part #, I was able to corroborate the CAS 3, or CL 3, or CLASS 3 latency thing.

That's why I ordered the WINTEC RAM.

Otherwise, I would never have dared to.

At the moment, without looking at the actual DIMM, I can't seem to locate the part #.

Tomorrow I will address both of those issues.

All the best, and forget about the rest,

DJ

 

[cdogg]

Nah, you don't have to do all that. I was just curious. Didn't mean to sound like I didn't believe ya! I've heard of stranger things...

~cdogg
"Insanity: doing the same thing over and over again and expecting different results." - Einstein
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