DDR2 CAS Latency - Speed versus Latency

Tipstaff · May 8, 2006, 05:05 AM

I got my nice X1600XT by FedEx Friday, and since then I've been looking at a couple of parts I'd need in order to get the ball rolling on using it. Those are: CPU, motherboard, and ram. I sort of have the motherboard figured out based on the need for not only Crossfire support, but also one that will support the Core 2 Duo (Conroe) when it comes out. Plus, what can I say, I'm Intels b!tch. So, I can either wait for the 965 boards to come out, or pickup one of the 975x boards, and grab a CPU for now which I can easily sell off later (probably a Pentium D 930 or 940).

Now, if I do buy the 975x based board I figure I have 2 options: the Intel D975XBX (rev. 3.04+), or the Asus P5WD2-E Premium. The Intel D975XBX supports DDR2 running at either 533, and 667mhz, while the Asus P5WD2-E Premium supports 533, 667, and 800mhz DDR2.

Here's where it gets interesting. One would think that the faster the ram the better, however, the biggest issue with DDR2 at the moment is Cas Latency. The lowest I've seen is CAS3, the highest, CAS5. Problem is that most CAS3 DDR2 runs at 533mhz, most 667mhz runs at CAS4 and CAS5 (especially the cheaper stuff) with some of the more expensive running at CAS3 (OCZ has some), and 800mhz DDR2 running between CAS4, and CAS5 (5 being the norm). There is also the $ and stock factor. Faster timed, faster mhz is hard to find in anything but the mucho $$ range.

So, which is the better route? Slower memory with faster CAS timings, or faster memory with slower CAS timings?

In gaming I've seen slower DDR with fast timings (333mz, CAS2.5) perform faster than fast ram with slow timings (400mhz, CAS3). With desktop apps like Photoshop, and Premiere it's the reverse. I've even seen reviews where even higher DDR was tested (500/400/333) where the 400mhz memory with faster timings out performed the 500mhz higher latency memory in exactly the same way. Going with that experience I'm inclinde to think that the 667mhz DDR2 with CAS3 timings would be my best bet, and in the case of the Intel D975XBX board, my only choice if I want the most out of it.

Any thoughts?

PangingJr · May 8, 2006, 10:08 PM

unless you're really need to have a new computer right now. i would wait until the new Intel CPU is released.

i'd say wait for Vista as well (you probably won't), but, by that time i think, you might want to use the Vista under a 4 GB system (rather than on a 2 GB system), and 2x 2GB of RAM kits should be more available then...

sorry, have no comment on the DDR2 CAS Latency - Speed versus Latency.

Ferret_Style · May 9, 2006, 05:52 AM

Honestly i have ddr 667 in mine on the asus board you have listed... it is amazingly fast and has a TON of good features. As for timings... i have not noticed any latency with the 667 and mine is set to 4-4-4-10 (i think that is right) there are faster memory at the same speed but they are quite expensive.

swimtech · May 9, 2006, 08:01 PM

You're on the right track (of course...) Tip, as I understand it from OCZs own FAQ, each CL number is one clock cycle, so memory running at 800Mhz taking 5 clock cycles (CL5 memory...) would access/move data more slowly than 667Mhz memory rated CL3, percentage wise...

Without using division involving long numbers and zeros behind decimal points, it seems that the easiest way would be to calculate relative speeds using percentages. As a for instance, 400Mhz memory at CL2 would mathematically perform more slowly than 667 Mhz memory at CL3 because the the speed increase (400 to 667 Mhz) is greater (59.97%) than the cache latency decrease (50%) for a net increase of 9.97% - right? As AMD knows, until DDR2 gets to 1Ghz at CL5, 400Mhz DDR2 at CL 2 is mathematically just as fast. There are other smaller considerations, but those are the two that matter most...

Seems you have already found the speed/latency "sweet spot" for current DDR2 memory at 667 CL3 (not counting overclocked speeds and manual latency tweaks...). So, the answer to your question is either one (speed or latency) - depending on the flexibility of the board and the memory. The "sweet spot" is a moving target though...

Most folks with the highest benchmark scores have increased latencies and overcome the difference by ramping the clocks on up. But I'm probably telling you stuff you already know...

Tipstaff · May 10, 2006, 11:39 AM

So far the hardest thing has been to find 1GB sticks that have CL3 timings. Almost all 667mhz (or 675mhz) DDR2 that have those timings are 512mb. However, in doing some research I've also found something of interest: most pieces of DDR2 spec'd to have CL3 has it's SPD clocked at CL4. Corsairs CM2X512A-5400UL is one such case (which, btw, the TWIN2X1024A-5400UL kit is just 2 of the CM2X512As). Over and over I found the same info popping up, and I even talked to Intel about it too, and the same thing came up.

There were, however, 2 exceptions: OCZs DDR2 PC2-5400 Platinum Enhanced Latency XTC (3-3-3-15), and Mushkins XP2-5300 Extreme Performance (3-3-3-10) series. The OCZ set is brand spanking new, and are very, very hard to find in sizes other than 512mb or 1GB kits (2x512), and the Mushkin set just happens to be just as hard to find.

I'm starting to think that my only real option is to buy a nice and fast pair of OCZ CL4 sticks, and try tweaking the timings to see what I can get outta them. Only problem is that this dumps the Intel board since they are more stable when going by the SPD timings. As such I'm leaning towards the Asus board more and more (I came to the realization that if I go with a Crossfire setup, or any dual card setup, that on the Intel board, thanks to the placement of the PCIE slots, that I will lose 1 of the 2 PCI slots, which means I have to choose between having a good sound card, or having wireless networking... with the Asus board I don't have this problem).

Thank God I'm not rushing this, and have time to decide on what to get.

swimtech · May 13, 2006, 04:59 AM

Saw that Crucial has some 3-3-3-12 1 gig Ballistix modules both individually and as a kit (2x1gig kit) available, but somewhat expensive - the Mushkin is cheaper... Also, prices on this type memory look to be going up over the past month.

Tipstaff · May 13, 2006, 05:54 AM

Quote:

Originally Posted by swimtech

Saw that Crucial has some 3-3-3-12 1 gig Ballistix modules both individually and as a kit (2x1gig kit) available, but somewhat expensive - the Mushkin is cheaper... Also, prices on this type memory look to be going up over the past month.

Yeah, I noticed that recently too. The Crucial set would run about $325 or so (my cost). I also noticed that NCIX has 1 open box version for $290, which I'm considering buying.

Get a load of this: I got a very interesting phone call from Intel earlier this week, and my rep was offering a nice bundle set which consisted of an Intel D975XBX mobo, a Pentium D 820 (2.8ghz, 2x1mb cache), Microsofts Windows XP MCPE (latest 3 disc version), an MCPE remote/receiver, and one of the new Remote Keyboard for Windows XP MCPE wireless keyboards. How much? $430. $430 for $700 worth of product. I couldn't say YES!!! fast enough. Well, it came in today, and the beauty of it all is that I didn't get dinged for taxes or anything at the boarder. Too sweet.

So, I'm going to keep the motherboard, and put a system together for a customer with the other parts paired with a 945 mobo (although, I might keep the keyboard too.. sweet looking board).

moeness86 · May 13, 2006, 09:31 AM

that's just ... nice

but plz does anyboD know any exact method to judge speed - latency calculations ?

Chaos · May 13, 2006, 03:16 PM

This may be some help or at least an insight.

http://www.ece.ualberta.ca/~elliott/...esentation.pdf

Tipstaff · May 13, 2006, 08:11 PM

Well, thanks to Viking posting that review BigBruin did on the OCZ 1GB Gold & Platinum XTC PC2 5400 DDR2 memory kits, and to see how close the scores were, I think I might go with the Gold XTC 2Gb kit. My cost on it would be around $260, plus there is a $35 mail in rebate that is good until May 21rst.

Now all I need is to get the CPU, plus another X1600XT, and I'm set.

swimtech · May 14, 2006, 03:38 AM

Awesome deal from your Intel rep - the sweetness of that deal money wise simply blows the need for all the tweaky research away - that can be a relief... You should be able to stick a nifty Core2 CPU in that board later too. The CAS 3 OCZ Ram is a great choice at a good price.

Tipstaff · May 14, 2006, 05:41 AM

Quote:

Originally Posted by swimtech

Awesome deal from your Intel rep - the sweetness of that deal money wise simply blows the need for all the tweaky research away - that can be a relief... You should be able to stick a nifty Core2 CPU in that board later too. The CAS 3 OCZ Ram is a great choice at a good price.

Actually, the OCZ Platnium is CL3, and the Gold is CL4. However, according to the review BigBruin did comparing the 2 brands shows that the difference in performance is minimal. Going on that I'm thinking of buying the Gold to save some money.

One thing about the mobo: I completely forgot to check the revision date on it. I still can't believe I did that. If it's below revision 3.04 I'm screwed as anything before that won't work with the Core 2s. Unfortunately I won't be able to find out until Wed/Thurs next week (doing offsite work). I seriously hope it is one of the compatible Core 2 boards.

Not to worry though. I can easily sell the parts if I need to.

mike2h · May 14, 2006, 06:26 AM

if you decide to go with the asus you might want to wait another month. there are still the last rev in channels & those are reported to not be conroe compatible. cant remember were i read this but you might want to check it out. it is the main reason i have been leaning towards the intel mb. that and i am truly intersted to see what intel has done with a board made for us performance/oc types - while still keeping their rep for solid dependability/stability.

sorry did not see your above post.

i think you ocz gold choice is the best. i'm looking at the same thing you are. wished we knew how conroe is going to oc

swimtech · May 14, 2006, 09:28 PM

Sorry Tip, was noting the review link, not your explicit response - that you had decided on the OCZ Gold - considering the review a wise choice for value, of course, and once NewEgg gets it back in stock looks like it'll be less than 200.00

Of most all the reviews I've seen for quite some time, the review you linked to at BigBruin is very informative on the subject of speed vs latency (relating to DDR2...) because the memory is so much alike. Looks as though speed is the biggest factor determining overall performance with that memory type for now (...and on the Intel platform...). For now too, as you're finding, the mainboard is a big factor in determining what memory to use. Your concern with the SPD issue you mention and other timing issues (also referenced at Anandtech and elsewhere) are applicable to a lot of boards right now.

Tipstaff · May 17, 2006, 04:55 AM

Well, so much for that D97XBX board. Seems that the reason it was such a great deal is because it's an older revision board (rev. 3.02 infact) that doesn't support the upcoming Conroe "Core 2 Duo" CPU. Oh well.

At least I got the ram for when I do get the board I want.

mike2h · May 17, 2006, 05:48 AM

that is what i am worried about. just ordered the same board from tiger direct. hoping their big enough that they have a lot of turnover & have the newer boards in stock.

Tipstaff · May 17, 2006, 06:47 AM

Quote:

Originally Posted by mike2h

that is what i am worried about. just ordered the same board from tiger direct. hoping their big enough that they have a lot of turnover & have the newer boards in stock.

I might (and I say that with very little confidence) be able to get Intel to switch it for me. Awhile back I had a problem upgrading a CPU on an 865 motherboard. According to the specs you had to have a board with a later revision inorder to support the processor, and the board this customer had was just below the specs (and the CPU for sure didn't work on it). Intel was kind enough to switch it for me calling it a warranty replacement. I'll have to see if they will be "kind" enough to do it again.

May 8, 2006, 05:05 AM	#1
Tipstaff HardwareHeaven Extreme Member Join Date: Jul 2002 Location: Real capital of Canada: Torauna Posts: 6,773 Rep Power: 190 System Specs	DDR2 CAS Latency - Speed versus Latency I got my nice X1600XT by FedEx Friday, and since then I've been looking at a couple of parts I'd need in order to get the ball rolling on using it. Those are: CPU, motherboard, and ram. I sort of have the motherboard figured out based on the need for not only Crossfire support, but also one that will support the Core 2 Duo (Conroe) when it comes out. Plus, what can I say, I'm Intels b!tch. So, I can either wait for the 965 boards to come out, or pickup one of the 975x boards, and grab a CPU for now which I can easily sell off later (probably a Pentium D 930 or 940). Now, if I do buy the 975x based board I figure I have 2 options: the Intel D975XBX (rev. 3.04+), or the Asus P5WD2-E Premium. The Intel D975XBX supports DDR2 running at either 533, and 667mhz, while the Asus P5WD2-E Premium supports 533, 667, and 800mhz DDR2. Here's where it gets interesting. One would think that the faster the ram the better, however, the biggest issue with DDR2 at the moment is Cas Latency. The lowest I've seen is CAS3, the highest, CAS5. Problem is that most CAS3 DDR2 runs at 533mhz, most 667mhz runs at CAS4 and CAS5 (especially the cheaper stuff) with some of the more expensive running at CAS3 (OCZ has some), and 800mhz DDR2 running between CAS4, and CAS5 (5 being the norm). There is also the $ and stock factor. Faster timed, faster mhz is hard to find in anything but the mucho $$ range. So, which is the better route? Slower memory with faster CAS timings, or faster memory with slower CAS timings? In gaming I've seen slower DDR with fast timings (333mz, CAS2.5) perform faster than fast ram with slow timings (400mhz, CAS3). With desktop apps like Photoshop, and Premiere it's the reverse. I've even seen reviews where even higher DDR was tested (500/400/333) where the 400mhz memory with faster timings out performed the 500mhz higher latency memory in exactly the same way. Going with that experience I'm inclinde to think that the 667mhz DDR2 with CAS3 timings would be my best bet, and in the case of the Intel D975XBX board, my only choice if I want the most out of it. Any thoughts? __________________ Portal: The Flash Version _________________________________ Brain: So, you sacked the cocky khaki Kicky Sack sock plucker? Mr. Sackett: The second cocky khaki Kicky Sack sock plucker I've sacked since the sixth sitting sheet slitter got sick. Last edited by Tipstaff; May 8, 2006 at 05:45 AM.

May 9, 2006, 08:01 PM	#4
swimtech HardwareHeaven Extreme Member Join Date: May 2002 Location: North Carolina Posts: 4,040 Rep Power: 124 System Specs	You're on the right track (of course...) Tip, as I understand it from OCZs own FAQ, each CL number is one clock cycle, so memory running at 800Mhz taking 5 clock cycles (CL5 memory...) would access/move data more slowly than 667Mhz memory rated CL3, percentage wise... Without using division involving long numbers and zeros behind decimal points, it seems that the easiest way would be to calculate relative speeds using percentages. As a for instance, 400Mhz memory at CL2 would mathematically perform more slowly than 667 Mhz memory at CL3 because the the speed increase (400 to 667 Mhz) is greater (59.97%) than the cache latency decrease (50%) for a net increase of 9.97% - right? As AMD knows, until DDR2 gets to 1Ghz at CL5, 400Mhz DDR2 at CL 2 is mathematically just as fast. There are other smaller considerations, but those are the two that matter most... Seems you have already found the speed/latency "sweet spot" for current DDR2 memory at 667 CL3 (not counting overclocked speeds and manual latency tweaks...). So, the answer to your question is either one (speed or latency) - depending on the flexibility of the board and the memory. The "sweet spot" is a moving target though... Most folks with the highest benchmark scores have increased latencies and overcome the difference by ramping the clocks on up. But I'm probably telling you stuff you already know... __________________ It's not so much getting your way that matters or not - what matters is how you go about getting it.

May 10, 2006, 11:39 AM	Thread Starter #5
Tipstaff HardwareHeaven Extreme Member Join Date: Jul 2002 Location: Real capital of Canada: Torauna Posts: 6,773 Rep Power: 190 System Specs	So far the hardest thing has been to find 1GB sticks that have CL3 timings. Almost all 667mhz (or 675mhz) DDR2 that have those timings are 512mb. However, in doing some research I've also found something of interest: most pieces of DDR2 spec'd to have CL3 has it's SPD clocked at CL4. Corsairs CM2X512A-5400UL is one such case (which, btw, the TWIN2X1024A-5400UL kit is just 2 of the CM2X512As). Over and over I found the same info popping up, and I even talked to Intel about it too, and the same thing came up. There were, however, 2 exceptions: OCZs DDR2 PC2-5400 Platinum Enhanced Latency XTC (3-3-3-15), and Mushkins XP2-5300 Extreme Performance (3-3-3-10) series. The OCZ set is brand spanking new, and are very, very hard to find in sizes other than 512mb or 1GB kits (2x512), and the Mushkin set just happens to be just as hard to find. I'm starting to think that my only real option is to buy a nice and fast pair of OCZ CL4 sticks, and try tweaking the timings to see what I can get outta them. Only problem is that this dumps the Intel board since they are more stable when going by the SPD timings. As such I'm leaning towards the Asus board more and more (I came to the realization that if I go with a Crossfire setup, or any dual card setup, that on the Intel board, thanks to the placement of the PCIE slots, that I will lose 1 of the 2 PCI slots, which means I have to choose between having a good sound card, or having wireless networking... with the Asus board I don't have this problem). Thank God I'm not rushing this, and have time to decide on what to get. __________________ Portal: The Flash Version _________________________________ Brain: So, you sacked the cocky khaki Kicky Sack sock plucker? Mr. Sackett: The second cocky khaki Kicky Sack sock plucker I've sacked since the sixth sitting sheet slitter got sick.

May 13, 2006, 04:59 AM	#6
swimtech HardwareHeaven Extreme Member Join Date: May 2002 Location: North Carolina Posts: 4,040 Rep Power: 124 System Specs	Saw that Crucial has some 3-3-3-12 1 gig Ballistix modules both individually and as a kit (2x1gig kit) available, but somewhat expensive - the Mushkin is cheaper... Also, prices on this type memory look to be going up over the past month. __________________ It's not so much getting your way that matters or not - what matters is how you go about getting it.

May 13, 2006, 09:31 AM	#8
moeness86 DriverHeaven Junior Member Join Date: Apr 2006 Location: Cairo Posts: 75 Rep Power: 0	that's just ... nice but plz does anyboD know any exact method to judge speed - latency calculations ? __________________

May 8, 2006, 10:08 PM	#2
PangingJr Member Join Date: Mar 2003 Posts: 5,989 Rep Power: 71	unless you're really need to have a new computer right now. i would wait until the new Intel CPU is released. i'd say wait for Vista as well (you probably won't), but, by that time i think, you might want to use the Vista under a 4 GB system (rather than on a 2 GB system), and 2x 2GB of RAM kits should be more available then... sorry, have no comment on the DDR2 CAS Latency - Speed versus Latency.

May 13, 2006, 03:16 PM	#9
Chaos Number Nine Join Date: May 2002 Location: Nova Scotia Posts: 5,268 Rep Power: 167 System Specs	This may be some help or at least an insight. http://www.ece.ualberta.ca/~elliott/...esentation.pdf __________________

May 13, 2006, 08:11 PM	Thread Starter #10
Tipstaff HardwareHeaven Extreme Member Join Date: Jul 2002 Location: Real capital of Canada: Torauna Posts: 6,773 Rep Power: 190 System Specs	Well, thanks to Viking posting that review BigBruin did on the OCZ 1GB Gold & Platinum XTC PC2 5400 DDR2 memory kits, and to see how close the scores were, I think I might go with the Gold XTC 2Gb kit. My cost on it would be around $260, plus there is a $35 mail in rebate that is good until May 21rst. Now all I need is to get the CPU, plus another X1600XT, and I'm set. __________________ Portal: The Flash Version _________________________________ Brain: So, you sacked the cocky khaki Kicky Sack sock plucker? Mr. Sackett: The second cocky khaki Kicky Sack sock plucker I've sacked since the sixth sitting sheet slitter got sick.

May 14, 2006, 03:38 AM	#11
swimtech HardwareHeaven Extreme Member Join Date: May 2002 Location: North Carolina Posts: 4,040 Rep Power: 124 System Specs	Awesome deal from your Intel rep - the sweetness of that deal money wise simply blows the need for all the tweaky research away - that can be a relief... You should be able to stick a nifty Core2 CPU in that board later too. The CAS 3 OCZ Ram is a great choice at a good price. __________________ It's not so much getting your way that matters or not - what matters is how you go about getting it.

May 14, 2006, 06:26 AM	#13
mike2h DriverHeaven Extreme Member Join Date: Nov 2002 Location: norcal Posts: 6,483 Rep Power: 91 System Specs	if you decide to go with the asus you might want to wait another month. there are still the last rev in channels & those are reported to not be conroe compatible. cant remember were i read this but you might want to check it out. it is the main reason i have been leaning towards the intel mb. that and i am truly intersted to see what intel has done with a board made for us performance/oc types - while still keeping their rep for solid dependability/stability. sorry did not see your above post. i think you ocz gold choice is the best. i'm looking at the same thing you are. wished we knew how conroe is going to oc __________________ Last edited by mike2h; May 14, 2006 at 09:37 PM.

May 14, 2006, 09:28 PM	#14
swimtech HardwareHeaven Extreme Member Join Date: May 2002 Location: North Carolina Posts: 4,040 Rep Power: 124 System Specs	Sorry Tip, was noting the review link, not your explicit response - that you had decided on the OCZ Gold - considering the review a wise choice for value, of course, and once NewEgg gets it back in stock looks like it'll be less than 200.00 Of most all the reviews I've seen for quite some time, the review you linked to at BigBruin is very informative on the subject of speed vs latency (relating to DDR2...) because the memory is so much alike. Looks as though speed is the biggest factor determining overall performance with that memory type for now (...and on the Intel platform...). For now too, as you're finding, the mainboard is a big factor in determining what memory to use. Your concern with the SPD issue you mention and other timing issues (also referenced at Anandtech and elsewhere) are applicable to a lot of boards right now. __________________ It's not so much getting your way that matters or not - what matters is how you go about getting it.

May 17, 2006, 04:55 AM	Thread Starter #15
Tipstaff HardwareHeaven Extreme Member Join Date: Jul 2002 Location: Real capital of Canada: Torauna Posts: 6,773 Rep Power: 190 System Specs	Well, so much for that D97XBX board. Seems that the reason it was such a great deal is because it's an older revision board (rev. 3.02 infact) that doesn't support the upcoming Conroe "Core 2 Duo" CPU. Oh well. At least I got the ram for when I do get the board I want. __________________ Portal: The Flash Version _________________________________ Brain: So, you sacked the cocky khaki Kicky Sack sock plucker? Mr. Sackett: The second cocky khaki Kicky Sack sock plucker I've sacked since the sixth sitting sheet slitter got sick.

May 17, 2006, 05:48 AM	#16
mike2h DriverHeaven Extreme Member Join Date: Nov 2002 Location: norcal Posts: 6,483 Rep Power: 91 System Specs	that is what i am worried about. just ordered the same board from tiger direct. hoping their big enough that they have a lot of turnover & have the newer boards in stock. __________________