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Topic Title: Best 2GB or 1GB module for S2895
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Created On: 06/18/2005 07:18 PM
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 06/18/2005 07:18 PM
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yulius
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I've been looking for A memory module that's preferably 2GB (1GB minimum) that's single rank, has a CAS latency of less than 3, and at 400MHz (or PC3200) for the S2895. And I'd like reliable memories from perhaps kingston, crucial, corsair, OCZ or any other reliable brands. Do they exist?

The closest I've found is the KVR400S4R3AK2/1G kingston value ram, which is a 400MHz, 1GB, Single Rank, but has a CAS latency of 3...

The one that I hope will fit all the specs is KRX3200AK2/2G also from kingston, but there is no rank specification from Kingston. And the technicians there give weird answers, such as "it is dual rank because it is a DIMM, a dual inline memory module." /huh.gif' border='0' style='vertical-align:middle' alt='huh.gif' /> and "kingston produce two kinds of this module, the dual and the single rank" /blink.gif' border='0' style='vertical-align:middle' alt='blink.gif' /> , and according to this page: http://www.valueram.com/memoryranks/default.asp' ">http://www.valueram.com/memoryranks/default.asp a 72-bit module is a single rank, but almost every dual ranks were 72-bit according to the datasheets of the RAMs in this page: http://www.ec.kingston.com/eco...urat...&submit1=Search' ">http://www.ec.kingston.com/eco...butor=0&submit1=Search /wacko.gif' border='0' style='vertical-align:middle' alt='wacko.gif' />
Kingston only has rank information for the kingston value ram modules (those starting with KVR, but what about the KRX? Or can anyone recommend me other modules that can fit the specs I wanted? Thanks.

yulius
 07/11/2005 05:47 AM
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Pablov
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HI,

maybe you already bought something.....

I have KRX3200ak2/1G (on Tiger K8W S2875)
The default timing for this kit running at ddr 400 is CAS 3 (not 2.5 as stated by kingston).
The default timing when running at DDR 333 is Cas 2.5 (as stated)

This happens at least with my modules (bought on 2004, and bit different than the ones available. I noticed that are slightly different because the default timings are 2.5-3-3-8-1 instead of 2.5-3-3-6-1 as appears now in Kingston's website)

On the Bios setup of the Tiger K8w now you can set the memory timings, so I can set it to 2.5 when running at ddr 400. And it works fine. I even tested it to run at Cas 2 and it did it well. But I also did run SiSoft Sandra at all Cas latencies and didn't notice any significant improvement in memory benchmarks.

Besides this point, I would like to say: think well before you buy a module. Keep in mind the future upgrades you would like to do.
There are differences in price between the KRX and the KRV series. If you don't have any problem to spend a lot of money, then buy whatever you want.
If you want to spend less money then the KRV series could be better.

It is very recomended to use the same Timings in ALL memory modules.
So if you buy KRX and later want to upgrade memory, you should buy another KRX kit wich is more expensive than krv.

My case is : I have Tiger K8W S2875 and KRX3200AK2/1G.
Now I want to add more RAM, but don't want to spend the astronomic price that KRX3200AK/2G is.
I want to add 2 GB to complete the 4 dimms, so I will buy KVR400S4R3A/1G x 2 (2 modules). The timings are different from KRX, but I guess I can set right values for all modules because the Bios setup in my motherboard let me adjust it.

(If the KVR400S4R3A/1G doesn't work well at 2.5 then I will set 3-3-3)

The recommendation from Tyan is that All memory modules have the same Size/Timings and brand for best performance, and to avoid any conflicts.

Corsair has cheaper modules with latency 2.
Maybe you could check if someone in this board is using them and ask him/her the results.

I prefer to buy Kingston because in my country Kingston has direct Dealer (corsair has not) and I can buy it easily and at good price.

I will take the risk to mix krx with krv but just because I can set the timing in the bios setup. I hope everything works fine.....

If I could choose from the beginning, then I would buy KRV not krx, so I could upgrade Ram paying a logical amount of money.

It is a GOOD IDEA to buy the memory in PAIRS, to use them in dual-channel mode. Sometimes stisks are bit different if you buy them in different times.

I will appreciate VERY much if you tell me your decision and experience.

(Maybe some day I could buy a Thunder K8WE... (and will use the KRV modules that I will buy and put on my actual Tiger.... That is a good thing from Kingston..... it is compatible for almost all Tyan motherboards)).
 07/11/2005 09:43 AM
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yulius
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Hi,
thank you very much for your reply, I thought nobody saw my post. Well, this sounds crazy but I don't have much experience in building my own pc, as this is the first pc I am going to build. I was just hoping that the pc is something upgradable for the future.
you said that corsair has memory modules at CAS 2, but are they at least 1GB modules? I need big memory modules for upgradability. I'll buy the best modules I can find for that. Do you know about ranks? that can limit upgradability big time too (by half), that's why I want single ranked dimms. do you know whether the KRX is a single or dual rank?
i don't mind spending a lot on the krx coz prices fall, and I am not upgrading every 6 months. I think you made the right decision.
i will tell you what i know once I start assembling. In the mean time I need to know the fastest RAM I could possibily get at at least 1GB, and single ranked. I'd appreciate it if anyone can tell me that.
thank you for your very helpful post Pablov. I will definitely do some adjustments, to improve the CAS if necessary and also if I made sure the krx is single ranked.

yulius
 07/12/2005 11:11 PM
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djmorgan
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QUOTE(yulius @ Jun 18 2005, 04:18 PM)I've been looking for A memory module that's preferably 2GB (1GB minimum) that's single rank, has a CAS latency of less than 3, and at 400MHz (or PC3200) for the S2895. And I'd like reliable memories from perhaps kingston, crucial, corsair, OCZ or any other reliable brands. Do they exist?

The closest I've found is the KVR400S4R3AK2/1G kingston value ram, which is a 400MHz, 1GB, Single Rank, but has a CAS latency of 3...

yulius
[right][snapback]440344[/snapback][/right]


I've been driving myself insane looking at memory specs for the last week and have found no DDR400 2GB single rank modules anywhere, at any cost. Some of the chip makers web pages talk about them but I have not found any actually for sale.

For 1GB single rank DDR400 it's pretty slim pickings. Far and away the most common that is guaranteed to be single rank is the Kingston KVR400S4R3A/1G as you've found. I settled on this module for my system and now find that they aren't really that widely available -- there seems to be none in Canada, for example.

Other manufacturers either do not list any rank information or if they do, the parts are not available at a vendor that would actually stoop to sell you one. Argh! The only other one I've found is at Digikey from Micron (MT18VDDF12872G-40BD3) -- but at $470/GB it's a little steep!

I emailed patriot and the 1gb model PSD1G40018ER may (or may not) be single rank. The response did not fill me with a lot of confidence and I would confirm before ordering.

Viking has the VI4CR287224DCP (or EBP) is stated as single rank but I can't find one anywhere. Likewise with those from infineon, samsung, and netlist. I still have an email into PQI. I do not think Crucial has any 1GB single rank.

AMD could be a little more forthcoming with this information -- I was unaware of the 4 rank limit until I started putting together a system -- but of course they can't brag that they are breaking the 4GB barrier if they really haven't yet.

So after the little mini-rant, all I can say is that so far I've only found the Kingston KVR400S43A/1G to be absolutely single rank and anything like widely available. If you've found any others please report back here!

Good luck
Doug

 07/12/2005 11:48 PM
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yulius
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thanks for the information Doug...

I'll report back if I know anything else.

BTW, what is more important, CAS or the MHz?

thanks,
yulius
 07/13/2005 12:06 PM
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djmorgan
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QUOTE(yulius @ Jul 12 2005, 08:48 PM)thanks for the information Doug...

I'll report back if I know anything else.

BTW, what is more important, CAS or the MHz?

thanks,
yulius
[right][snapback]457892[/snapback][/right]


I'm far from an expert here but my understanding is that the CAS is measured in clock cycles, I.E. CAS=3 = 3 clock cycles. For DDR400 I believe the clock is 200MHZ and CAS is measured in whole cycles so the column delay would be roughly 15ns while DDR333 would be roughly 18ns. All other timings would also be more nanoseconds for the lower clock rate besides just CAS.

So with everything else being equal DDR400 is about 20% faster than DDR333 which would lead me to believe a DDR400 CAS of 3 is the same amount of time as a DDR333 CAS of 2.5.

Doug


 07/13/2005 07:03 PM
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yulius
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Thanks Doug, for the explanation.

where did you find the info about VI4CR287224DCP being single ranked?
I can't find it, not even on the viking website. But I did find VI4CR287224DBP on the website though. Are you by any chance referring to the "DBP" instead?

yulius
 07/13/2005 11:33 PM
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djmorgan
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QUOTE(yulius @ Jul 13 2005, 04:03 PM)Thanks Doug, for the explanation.

where did you find the info about VI4CR287224DCP being single ranked?
I can't find it, not even on the viking website. But I did find VI4CR287224DBP on the website though. Are you by any chance referring to the "DBP" instead?

yulius
[right][snapback]458380[/snapback][/right]


I found the information by clicking "DRAM Product Guide" on the far right under quicklinks, then clicked the button marked DDR1. The page will be unbuffered ram (not of interest to us) but if you move your mouse over the DDR1 button on this page you will have a drop down menu that includes "Registered DIMM" which is what we want. If you look under the PC3200 table you'll find the two modules I referenced. I have no idea what JEDEC R/C means but that seems to be the difference.


I was going to add to this thread anyway to say that I'm getting more conflicting information about this rank business.

From patriot memory I got the following response to my follow up to my original query:

QUOTE:
Doug,

It should be 8 rank per CPU. Normally each CPU is able to handle up to
16GB with the setup of 4GB (2rank module) X 4 slots. Therefore dual CPU
is able to take 32GB total memory support. Of course it depends on the
chipset of the motherboard design as well.

Yes, PSD1G40018ER is good for AMA Opteron 4GB setup.

Regards,
Tech support
END QUOTE

I've been looking into it a little more and though AMD's knowledge base is strangely silent on the subject another post in these forums sheds a little more light on it: http://forums.amd.com/index.php?showtopic=44168' ">http://forums.amd.com/index.php?showtopic=44168

About mid-way down they talk about the reason for the limit and that it might not be a hard and fast rule. I was going to email AMD support tonight as I do not have the "Ex" series of stepping codes and don't know if what the "CG" 250 can handle more than 4 ranks per cpu.

Unfortunately this information may be too little too late for me as I've already ordered 4GB of memory (the first mentioned Kingston single rank 1G's).

I can post the response from AMD back here if you are interested.

Good luck
Doug

 07/14/2005 12:51 AM
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yulius
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I'd really appreciate it if you can post it here, Doug. /smile.gif' border='0' style='vertical-align:middle' alt='smile.gif' />

According to Kingston, each cpu can only take 4 ranks. http://www.ec.kingston.com/eco...urat...&submit1=Search' ">http://www.ec.kingston.com/eco...butor=0&submit1=Search

I really hope they are wrong

So far, I think you made the right decisions with the kingston modules, I 'd also get those if I am in a hurry.

I think I need to do more readings as to what steppings mean.
I still got lots of things to learn about about building a computer. sigh...

thanks,
yulius
 07/14/2005 01:01 AM
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djmorgan
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I've read the Kingston info and also put a dozen different socket 940 motherboards into their memory selector program --- each one came back with 4 ranks maximum for DDR400. Since there are no 2GB single rank modules available that would mean 4GB maximum.

On the other hand the forum thread I referenced above seems to imply that it's not a set rule and like overclocking may or may not work depending on a variety of factors. Patriot memory and from what little I've found out about the motherboard I ordered (Monarch Computer A0110289 -- a cheapy) it looks like 8 ranks, which would either allow 4 cheaper dual rank 1GB or the expensive dual rank 2GB modules for a total of 8GB.

I'm going 2GB per processor to begin with and then maybe upping them both to 4GB depending on how it works with $ and Win64.

I put in a service request with AMD and will post back here when I get an answer.

I just find it odd that if this parameter is as critical as it sounds there would be a lot more information out about it, especially with windows 64 bit released.

Doug
 07/15/2005 01:03 PM
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djmorgan
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Update!

AMD got back to me and QUOTE:

Opteron processor architecture allows you to install more than 4 banks
of memory per each unit. So probably your motherboard does not support
it.
ENDQUOTE.

I also came across a preview of the FX57 which specified that AMD had updated the memory interface for this processor, strengthening my belief that the latest "E0" or higher versions of the processors probably have less issues with more than 4 memory ranks due to stronger pin drivers on the memory interface. http://www.extremetech.com/art.../0,1697,1831392,00.asp' ">http://www.extremetech.com/art.../0,1697,1831392,00.asp

I guess this is an electrical matter regarding the relative strength of the pin drivers on the actual processor (stronger with "E0"+) , the layout of the motherboard traces (distance, width, etc), and the organization and layout of the memory module (how many chips driven, type of chips, etc). My understanding is that unlike the pentiums there is no logic between the CPU and Memory, only the traces on the mobo so this issue would only apply to the AMD processors. Intel's memory constraints would be more a matter of the motherboard chipset.

The physical limit on the amount of memory like 8GB/16GB maximum or whatever that's quoted on the motherboard specs would be due to the maximum module sizes supported by the motherboard -- I.E. if a motherboard allowed 2GB modules then 8GB/Processor would be maximum.

I have yet to get a response regarding my motherboard but you might want to email both the motherboard manufacturer as well as the prospective memory supplier and see if you can find some other options. Myself I've got the "CG" processors and will stick to the Kingston single rank modules, four of which are somewhere between Quebec and British Columbia with my name on them.

In the TTL days it was pretty simple -- you had a fan-out of so many TTL loads and at the glacially slow speeds possible you could pretty much ignore transmission line effects if you were working on a single circuit board.

Good luck
Doug
 07/15/2005 02:42 PM
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yulius
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Wow, the new processors are good news. I read somewhere(probably from one of the links you gave me), that AMD said we should downclock the 400MHz to 333MHz if we want to fully load the memory slots with dual rank modules. Maybe we can do just that and next time, when we upgrade the processors, we can return it to the original speed again.

Does your motherboard have 2 or 1 cpu slot? coz since you only bought 4 modules, and if you have 4 more empty slots to fill for the other cpu, you can still get dual rank modules for all the other slots. What is/will your setup be(just curious)?

And regarding the CAS latency, I read somewhere that

CAS=column access time / (bus speed)^-1

so if the RAM is downclocked to 333MHz, it'll probably give a better CAS latency, assuming the column access time is not directly influenced by the bus speed(in other words, it remains constant). Is my assumption wrong?
But your post above states that a RAM with a higher bus speed, but higher latency can have the same speed as a RAM with a lower bus speed but lower latency(which I believe you are right). So, does that mean that CAS latency is not an absolute way of measuring the speed of RAM? Wouldn't the column access time be a better way then? so what's up with CAS latency?

thanks,
yulius
 07/15/2005 03:04 PM
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djmorgan
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QUOTE(yulius @ Jul 15 2005, 11:42 AM)Wow, the new processors are good news. I read somewhere(probably from one of the links you gave me), that AMD said we should downclock the 400MHz to 333MHz if we want to fully load the memory slots with dual rank modules. Maybe we can do just that and next time, when we upgrade the processors, we can return it to the original speed again.

Does your motherboard have 2 or 1 cpu slot? coz since you only bought 4 modules, and if you have 4 more empty slots to fill for the other cpu, you can still get dual rank modules for all the other slots. What is/will your setup be(just curious)?

And regarding the CAS latency, I read somewhere that

CAS=column access time / (bus speed)^-1

so if the RAM is downclocked to 333MHz, it'll probably give a better CAS latency, assuming the column access time is not directly influenced by the bus speed(in other words, it remains constant). Is my assumption wrong?
But your post above states that a RAM with a higher bus speed, but higher latency can have the same speed as a RAM with a lower bus speed but lower latency(which I believe you are right). So, does that mean that CAS latency is not an absolute way of measuring the speed of RAM? Wouldn't the column access time be a better way then? so what's up with CAS latency?

thanks,
yulius
[right][snapback]459895[/snapback][/right]

Yulius:

I've got a 2-socket motherboard with 2x 250's. So with 4GB I'll start off with 2GB per processor and 2 slots open. If I wait a while to upgrade the memory, maybe the 2GB modules will be cheap, but I kind of doubt it unless Microsoft's next release pigs out on memory like the Win98 -> XP upgrade. If I need to go to 4GB sooner I'll probably just get somemore Kingston modules.

As per the CAS -- remember that it is measured in clock cycles so it will vary with clock frequency. For DDR that's half the number -- I.E. DDR400 == 200MHZ. So your formula = CAS/FREQ = nanoseconds. CAS = 3/200,000,000=0.000000015 or 15ns.

Doug
 07/16/2005 05:41 PM
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Opteron
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QUOTE(djmorgan @ Jul 15 2005, 09:03 AM)Update!

AMD got back to me and QUOTE:

Opteron processor  architecture allows you to install more than 4 banks
of memory per each unit. So probably your motherboard does not support
it.
ENDQUOTE.
I think you forgot one thing...
Of course Opterons can handle more than 4 banks, but then only at DDR333.
Exceptional to this are the new E Revision CPUs, which are able to handle more than 4 banks with DDR400. That is you can run DDR400 timings with 4 dual rank modules, but it will add another cycel to the memory access. This is referred as "Command Rate" in most bioses and could be 1T or 2T. In the case of 4 dual rank modules, DDR400 (and an E-Rev. CPU) it must be set at 2 T. So you get more bandwidth, but worse access timings compared to DDR333 and 1T.
Well the differences should not be much, it will depend on the software you are using, which setting would suit you better.

For the overall topic for single rank modules, have a look at this pdf from AMD:
http://www.amd.com/us-en/asset...t_ty...ed_DIMM_AVL.pdf' ">http://www.amd.com/us-en/asset...egistered_DIMM_AVL.pdf
There you will find some more 1GB single rank modules, but no 2 GB modules at all.

I would personally prefer the Micron module. You can get it for ~$216 from Crucial' ">http://www.crucial.com/store/p...2Y40B&WSPN=CT12872Y40B , a subdivision of Micron. Depending on where you are living, some taxes and shipping will be added to that price, but I think it will be still a lot cheaper than the mentioned $470. According to that picture' ">http://store1.yimg.com/I/memx_1855_29182236, it is the single rank module from Micron. But better ask the Crucial support for 100% guarantee, before ordering. You may also ask the that online shop' ">http://www.memoryx.net/xdl1024.html directly, the modules are cheaper($190) there, too.
My last Micron Chips were very good at oc. They were specified for CL2 at 133 Mhz, and went up till 155 Mhz with that setting. Good old SDRAM times ... /smile.gif' border='0' style='vertical-align:middle' alt='smile.gif' /> What I want to say, maybe there is a slightly chance for the registered modules to run faster, too /smile.gif' border='0' style='vertical-align:middle' alt='smile.gif' /> The Micron modules are also made of modern BGA chips, instead of the old DIL chips.
If you purchase some Microns(and have not order some other modules, yet) , please let us know the result.

Have fun

Opteron

P.S.:Just as a note: You are luckly, there are not *any* unbuffered single rank modules. I just checked for a friend with a S939 system, and was very astonished ...
 07/16/2005 09:30 PM
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highlandsun
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QUOTE(Opteron @ Jul 16 2005, 01:41 PM)P.S.:Just as a note:  You are luckly, there are not *any* unbuffered single rank modules. I just checked for a friend with a S939 system, and was very astonished ...
[right][snapback]460703[/snapback][/right]


Yes, it's quite annoying.

By the way, when I benchmarked DDR333 CL2.5 vs DDR333 CL2 on a Pentium-M system I only saw a 1.6% difference in throughput (running SuperPI). I think if you count the total number of cycles required for a single memory access, you'll see that .5 cycles is pretty insignificant.

-------------------------
Asus A8V Deluxe, Opteron 185, 4xSamsung 1GB Reg/ECC DDR400, AC Freezer64 Pro, Antec Sonata case w/TruePower480
 07/17/2005 01:27 PM
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djmorgan
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QUOTE(Opteron @ Jul 16 2005, 02:41 PM)I think you forgot one thing...
Of course Opterons can handle more than 4 banks, but then only at DDR333.
Exceptional to this are the new E Revision CPUs, which are able to handle more than 4 banks with DDR400. That is you can run DDR400 timings with 4 dual rank modules, but it will add another cycel to the memory access. This is referred as "Command Rate" in most bioses and could be 1T or 2T. In the case of 4 dual rank modules, DDR400 (and an E-Rev. CPU) it must be set at 2 T. So you get more bandwidth, but worse access timings compared to DDR333 and 1T.
Well the differences should not be much, it will depend on the software you are using, which setting would suit you better.

For the overall topic for single rank modules, have a look at this pdf from AMD:
http://www.amd.com/us-en/asset...t_ty...ed_DIMM_AVL.pdf' ">http://www.amd.com/us-en/asset...egistered_DIMM_AVL.pdf
There you will find some more 1GB single rank modules, but no 2 GB modules at all.

I would personally prefer the Micron module. You can get it for ~$216 from Crucial' ">http://www.crucial.com/store/p...2Y40B&WSPN=CT12872Y40B  , a subdivision of Micron. Depending on where you are living, some taxes and shipping will be added to that price, but I think it will be still a lot cheaper than the mentioned $470. According to that picture' ">http://store1.yimg.com/I/memx_1855_29182236, it is the single rank module from Micron. But better ask the Crucial support for 100%  guarantee, before ordering. You may also ask the that online shop' ">http://www.memoryx.net/xdl1024.html directly, the modules are cheaper($190) there, too.
My last Micron Chips were very good at oc. They were specified for CL2 at 133 Mhz, and went up till 155 Mhz with that setting. Good old SDRAM times ... /smile.gif' border='0' style='vertical-align:middle' alt='smile.gif' /> What I want to say, maybe there is a slightly chance for the registered modules to run faster, too /smile.gif' border='0' style='vertical-align:middle' alt='smile.gif' /> The Micron modules are also made of modern BGA chips, instead of the old DIL chips.
If you purchase some Microns(and have not order some other modules, yet) , please let us know the result.

Have fun

Opteron

P.S.:Just as a note:  You are luckly, there are not *any* unbuffered single rank modules. I just checked for a friend with a S939 system, and was very astonished ...
[right][snapback]460703[/snapback][/right]


We started off talking about the DDR400 memory only as noted several times above. I think I also remarked that the "E0" processors were different and didn't have the same restrictions.

I would double check on the crucial memory --- it is not the same part number and from the configuration I would suspect that it is not single rank as it's not x4 or an 18 chip module like the one referenced by the AMD document.

I looked at so many memory modules I can't recall if Crucial responded or not. If crcucial is the one with the online chat thingy (I can't seem to locate it on the website) then they only make modules as large as 512mb in single rank -- but this may not include micron modules or I could be thinking about on of the other suppliers.

I think the small difference between the CAS 2.5 DDR333 and CAS 3 DDR400 is due to one of the other parameters as the column wait will be the same amount of time.

I've already got my kingston modules so I'm set but would be curious if I can use more widely available modules when expending memory beyond 4GB. I have the "CG" stepping codes but maybe this would give me an excuse to upgrade the processors as well! Though from what you are saying there may not be much of performance gain compared to just slowing down to DDR333

Thanks
Doug
 07/19/2005 10:39 AM
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Opteron
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QUOTE(djmorgan @ Jul 17 2005, 09:27 AM)...

I would double check on the crucial memory --- it is not the same part number and from the configuration I would suspect that it is not single rank as it's not x4 or an 18 chip module like the one referenced by the AMD document.

...

Thanks
Doug
[right][snapback]461314[/snapback][/right]


Well I wrote the Crucial Support, and after some confusion of the support guy ( he thoughts double sided equals double rank ), I got confirmation, that the already mentioned Crucial Part is the corresponding Micron Part:

QUOTE(Crucial Support)...
I'm really sorry for the confusion, that' s my mistake.

I though double sided and double ranked meant the same so i double checked with my tech support here and in fact this part CT12872Y40B.18LFD4 is a double sided stick single ranked you are right but we do as well CT12872Y40B.36LFG4 who is a double sided stick double ranked.

So in short:

MT18VDDF12872Y-40B == CT12872Y40B.18LFD4 (single rank, 18 chips)
MT36VDDF12872G-40B == CT12872Y40B.36LFG4 (double rank, 36 chips)

The last tricky thing will be ordering, cause the part numbers are almost identically. Crucial just lists the first part of it on its webshop which is similar for both kinds: CT12872Y40B

So for anybody who wants to buy them, I suppose best thing would be to contact Crucial directly(phone) and say, that you want the single rank(though double sided) CT12872Y40B.18LFD4 module /smile.gif' border='0' style='vertical-align:middle' alt='smile.gif' /> Lets hope that the price will be the same /rolleyes.gif' border='0' style='vertical-align:middle' alt='rolleyes.gif' />

@highlandsun
QUOTE(highlandsun)By the way, when I benchmarked DDR333 CL2.5 vs DDR333 CL2 on a Pentium-M system I only saw a 1.6% difference in throughput (running SuperPI). I think if you count the total number of cycles required for a single memory access, you'll see that .5 cycles is pretty insignificant.

Well you measurd throughput both times @DDR333. DDR333 or PC2700 has a throughput of 2.7 GByte/s. Either at CL2.5 or CL3, it will be 2.7GByt/s.
Reagarding your test application (Super-Pi) I have to say, that its code most often fits into the local CPU cache, depending on the mode of Super-Pi and your processor model you are using. So to sum it up, you see only a very small difference:

1st because you did not change the max bandwidth(e.g. to DDR400) of your RAM
2nd because the used code is (probably) fitting nicely into the processor's cache, and is not bandwidth stressing or generally memory demanding very much.

byebye

Opteron
 07/25/2005 05:43 PM
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HanShot1st
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FYI, finding registered ram with the kind of spec you want is next to impossible. You are almost always stuck with CasLat of 3 with 1gig or 2 gig sticks.

Here is what I have done. I have 4x512 sticks (two on order) of Corsair CMX512re-3500llpt. This is simply the best reg. ddr you can get ATM. Downside is obviously that only 512mb dual sided modules are available. But, and it's a big but, these sticks run 2-3-2-6 @ 417mhz+ with 2.6v. Simply the fastest registered ram you're gonna find.

My two current sticks have no problem running 2-2-2-6 with 2.8v. When I drop in the other two stick, the only performance hit I will take is going from 1t to 2t command rate.

I found the 1024kit of two matched CMX512re-3500llpt sticks for 289$, single sticks are over 200 a piece.

Expensive ram...
 07/26/2005 03:57 PM
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Opteron
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QUOTE(HanShot1st @ Jul 25 2005, 01:43 PM)...
My two current sticks have no problem running 2-2-2-6 with 2.8v.  When I drop in the other two stick, the only performance hit I will take is going from 1t to 2t command rate.

  I found the 1024kit of two matched CMX512re-3500llpt sticks for 289$, single sticks are over 200 a piece.

  Expensive ram...
[right][snapback]468108[/snapback][/right]

Just one note, this "2t" actually adds one cycle to the memory access. In other words CL 3, 1T is quiet the same as CL 2 and 2T.
If you then look at the price, I would go for single rank CL 3, 1 GByte modules.

Besides that, the mentioned Corsair modules were made of BH5 chips 2 years ago for S940 AthlonFX systems. Nowadays they are as scarce as hen's teeth.

byebye

Opteron
 07/26/2005 04:28 PM
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HanShot1st
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QUOTE(Opteron @ Jul 26 2005, 11:57 AM)Just one note, this "2t" actually adds one cycle to the memory access. In other words CL 3, 1T is quiet the same as CL 2 and 2T.
If you then look at the price, I would go for single rank CL 3, 1 GByte modules.

Besides that, the mentioned Corsair modules were made of BH5 chips 2 years ago for S940 AthlonFX systems. Nowadays they are as scarce as hen's teeth.

byebye

Opteron
[right][snapback]468861[/snapback][/right]



Whoa, command rate is NOT the same as cas latency. You are going to get much better performance running 2-x-x-x 2T than 3-x-x-x 1T. The tests have been done to show that 1T and 2T are not that much different in performance.

Also, the Corsair sticks are CH-5 from more like one year ago. And they are not that difficult to find. Best registered sticks made beside the OCZ stuff which was BH-5. Either way you need tons of volt to max them out, but with stock 2.6v they run nice speeds with low timings.
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