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A study of DDR400 chips

R

RaynorWolfcastle

Diamond Member
So with the prices of RAM dropping so sharply in the past few weeks I've been thinking of adding RAM to my system. If I had wads of cash for this I'd just get another stick of Corsair and be done with it. Unfortunately, i don't have wads of cash so I've been looking for a nice stick of RAM that won't break the bank. After reading the horror stories of the OCZ scandals I've decided to investigate the ICs used most commonly on RAM and see what specs they are really rated for.

These are all 256 MBit ICs meant to be used in a 32x8 *2 configuration, that is, these go into double sided 512 MB DIMMS

All ratings are posted in [freq]: [tCL]-[tRCD]-[tRP]-[tRAS] (in nS) / [tCL]-[tRCD]-[tRP]-[tRC]-[tRAS] (in cycles for operation at [freq]) / [mean voltage] ± [tolerance]
tCL CAS latency
tRCD RAS to CAS Delay
tRP RAS precharge

Note the the spec sheets include many more parameters but I am only including these as they are the most relevant to the end user (that is they are usually the only ones visible throught the BIOS)

Refer to Ars technica for further explanation of technical DRAM timing terms (or for an even more complete and technical description check the linked Winbond pdf, pp 20-25)
Here's what I've come up with (note that these are the maximum specified ratings for each IC):

Samsung
KH560838D-TCCC - 200 MHz : 15-15-15-40 / 3-3-3-8 / 2.6V ± 0.10V
source

Winbond
W942508CH-5 - 200 MHz: 15-15-15-40 / 3-3-3-8 / 2.6V ± 0.10V
W942508CH-6 - 166 MHz: 15-18-18-42 / 2.5-3-3-7 / 2.5V ± 0.20V
source

Infineon
HYB25D256800BT(L)-5 - 200 MHz: 12.5-15-15-40 / 2.5-3-3-8 / 2.6V ± 0.10V
(note that these are the timings for "DDR400A" operation which appears to have looser tolerances than the "DDR 400B" spec, Infineon has a chip spec'd for CAS 3 for "DDR400B" operation)
source

Hynix
HY5DU56822AT_D53 - 200 MHz: 15-15-15-40 / 3-3-3-8 / 2.6V ± 0.10V
source

Micron
MT46V32M8 - 200 MHz: 15-15-15-40 / 3-3-3-8 / 2.6V ± 0.10V
source

Mosel Vitelic
V58C2256804S - 200 MHz: 12.5-15-15-40 / 2.5-3-3-8 / 2.6V ± 0.10V
(note that these are the timings for "DDR400A" operation which appears to have looser tolerances than the "DDR 400B" spec, Mosel has a chip spec'd for CAS 3 for "DDR400B" operation)
source

Nanya
NT5DS32M8BT-5 - 200 MHz: 12.5-15-15-40 / 2.5-3-3-8 / 2.6V ± 0.10V
(note that these are the timings for "DDR400A" operation which appears to have looser tolerances than the "DDR 400B" spec, Nanya has a chip spec'd for CAS 3 for "DDR400B" operation)
source

Elpida
EDD2508AKTA-5C - 200 MHz: 15-18-18-40 / 3-3-3-8 / 2.6V ± 0.10V
source

I think that covers all the major manufacturers.

What does this mean
As you can see, DDR400 ICs all have nearly the same specs (save the 6ns Winbond chip which are actually PC2700). Furthermore all have ratings of 3-3-3-8 @ 200 MHz @ 2.6V (for DDR400B operation). Now the PCB used to make the memory stick are also important in the making of a solid memory stick, but it doesn not change the IC's characteristics; that is anyone who sells you a memory stick with tighter ratings than 2.5-3-3-8 is selling you overclocked ICs.

Bottom Line
It is likely that the reason Samsung and Crucial label their chips CAS3 is because they are more conservative than other manufacturers. The fact that most companies rate their chips for CAS 3 operation presumably indicates that no IC manufacturer has a huge edge on the others. Furthermore large companies (such as Samsung and Crucial) are usually conservative in their binnings so it is likely that Samsung or Crucial CAS 3 can do much better. Companies like Corsair, on the other hand, test their products inside out; they then release aggressively spec'd RAM which is much likely to be closer to its limits. Case in point, my Corsair 3200C2 uses 6ns Winbond chips (see above).

Conclusion for the cheap and the risk-loving
Buying Crucial or Samsung PC3200 seems like a much better deal than buying Corsair PC3200. Sure you're not guaranteed CAS 2 operation at PC3200. In the end, you're likely to get a nice overclocker that will do as well as the Corsair PC3200 or perhaps even better. People who are lucky with Samsung or Crucial PC3200 are getting chips that are equivalent to the ones in Corsair's higher end RAM (PC3500, PC3200LL).

-Chris

Additional Link
Intel DDR400 spec page

*edit* Corrected some bad links and a couple of small oversights, added Nanya chip specs
 
Nice research, very insitefull. I suspected that this was the case and that you have a hard time going wrong with real samsung or crucial chips.
 
I have a stick of Apacer 6 layer PCB Samsung TCC4 chips CL3 and I'm running it @DDR433 2.5-3-3-7 rock solid@2.6v and I paid $121 shipped and just ordered another for $105 shipped it's such a great value, therefore I couldn't agree more with your assessment 😀
 
Originally posted by: RaynorWolfcastle
So with the prices of RAM dropping so sharply in the past few weeks I've been thinking of adding RAM to my system. If I had wads of cash for this I'd just get another stick of Corsair and be done with it. Unfortunately, i don't have wads of cash so I've been looking for a nice stick of RAM that won't break the bank. After reading the horror stories of the OCZ scandals I've decided to investigate the ICs used most commonly on RAM and see what specs they are really rated for.

These are all 256 MBit ICs meant to be used in a 32x8 *2 configuration, that is, these go into double sided 512 MB DIMMS

All ratings are posted in [freq]: [tCL]-[tRCD]-[tRP]-[tRAS] (in nS) / [tCL]-[tRCD]-[tRP]-[tRC]-[tRAS] (in cycles for operation at [freq]) / [mean voltage] ± [tolerance]
tCL CAS latency
tRCD RAS to CAS Delay
tRP RAS precharge

Note the the spec sheets include many more parameters but I am only including these as they are the most relevant to the end user (that is they are usually the only ones visible throught the BIOS)

Refer to Ars technica for further explanation of technical DRAM timing terms (or for an even more complete and technical description check the linked Winbond pdf, pp 20-25)
Here's what I've come up with (note that these are the maximum specified ratings for each IC):

Samsung
KH560838D-TCCC - 200 MHz : 15-15-15-40 / 3-3-3-8 / 2.6V ± 0.10V
source

Winbond
W942508CH-5 - 200 MHz: 15-15-15-40 / 3-3-3-8 / 2.6V ± 0.10V
W942508CH-6 - 166 MHz: 15-18-18-42 / 2.5-3-3-7 / 2.5V ± 0.20V
source

Infineon
HYB25D256800BT(L)-5 - 200 MHz: 12.5-15-15-40 / 2.5-3-3-8 / 2.6V ± 0.10V
(note that these are the timings for "DDR400A" operation which appears to have looser tolerances than the "DDR 400A" spec, Infineon has a chip spec'd for CAS 3 for "DDR400B" operation)
source

Hynix
HY5DU56822AT_D53 - 200 MHz: 15-15-15-40 / 3-3-3-8 / 2.6V ± 0.10V
source

Micron
MT46V32M8 - 200 MHz: 15-15-15-40 / 3-3-3-8 / 2.6V ± 0.10V
source

Mosel Vitelic
V58C2256804S - 200 MHz: 12.5-15-15-40 / 2.5-3-3-8 / 2.6V ± 0.10V
source

I think that covers all the major manufacturers.

What does this mean
As you can see, DDR400 ICs all have nearly the same specs (save the 6ns Winbond chip which are actually PC2700). Furthermore all have ratings of 3-3-3-8 @ 200 MHz @ 2.6V. Now the PCB used to make the memory stick are also important in the making of a solid memory stick, but it doesn not change the IC's characteristics; that is anyone who sells you a memory stick with tighter ratings than 2.5-3-3-8 is selling you overclocked ICs.

Bottom Line
It is likely that the reason Samsung and Crucial label their chips CAS3 is because they are more conservative than other manufacturers. The fact that most companies rate their chips for CAS 3 operation presumably indicates that no IC manufacturer has a huge edge on the others. Furthermore large companies (such as Samsung and Crucial) are usually conservative in their binnings so it is likely that Samsung or Crucial CAS 3 can do much better. Companies like Corsair, on the other hand, test their products inside out; they then release aggressively spec'd RAM which is much likely to be closer to its limits. Case in point, my Corsair 3200C2 uses 6ns Winbond chips (see above).

Conclusion for the cheap and the risk-loving
Buying Crucial or Samsung PC3200 seems like a much better deal than buying Corsair PC3200. Sure you're not guaranteed CAS 2 operation at PC3200. In the end, you're likely to get a nice overclocker that will do as well as the Corsair PC3200 or perhaps even better. People who are lucky with Samsung or Crucial PC3200 are getting chips that are equivalent to the ones in Corsair's higher end RAM (PC3500, PC3200LL).

-Chris

Additional Link
Intel DDR400 spec page
Click to expand...


WoW, thats sum nice research! No wonder samsung/crucial/kingston label there DDR400 sticks as CL3.
 
Good Stuff RaynorWolfcastle as we use to try and keep track of RAM @ Lost Circuits.... I do believe for 3rd parties that Winbond 5nans is the fastest out there now with Samsung as the follow up... when the new Winbond was released, Corsair switched from Samsung to join some other major 3rd Parties
 
Thanks guys, it's nice to see other people appreciate this info 🙂

Celeryman - This also tells you that if you choose to go with a 3rd party board you should stay away from Crucial and Samsung as they keep their highest performing ICs to themselves.

DAPUNISHER - If you follow the link I put up for Samsung, you'll see that Samsung only rates the TCC4 chips for use with 3-4-4-8 (that is 15-18-18-40 in nS). :Q

humank - I'm not sure who's ICs Kingston uses but Kingston has traditionally been very conservative with their speed ratings.

LED - I suspect you are correct, since the implication of Micron having their own brand memory sticks is that they keep the highest performing sticks to themselves; all other manufacturers on the other hand pass all chips on to 3rd parties. That being said, I'm under the impression that Winbond has had DDR400 on the market for more time than any of the IC manufacturers (apart from maybe Samsung) they probably have had more time to tweak their chips for better yields (and by consequence, better overclocking potential). 🙂
 
All I know is when THUGSROOK says Corsair XMS3000 is the best, it's the best! 🙂

Nice research there RaynorWolfcastle ..
 
Originally posted by: zephyrprime
Nice job! What about Nanya? It seems like they're the top performer (or am I reading the numbers wrong?).
Click to expand...

Nanya, Mosel, and Infineon have ICs rated for CAS 2.5 in "DDR400A" operation but their specs are very similar to the other manufacturers' specs for DDR400. I wasn't able to find out the difference between DDR400A and DDR400B, but judging by the specs, it seems to me that the DDR400A has looser specs than DDR400B. Note that Winbond, Samsung, and Crucial never mention anything about DDR400A or DDR400B, they just talk about DDR400.

If someone can shed some light on this DDR400A - DDR400B thing I would very much appreciate it 🙂
 
Excellent compilation, saving this for reference!

The most comprehensive review I've ever found of DDR333 & DDR400 memory (30 pages) is at hardwareluxx for those who are interested.
 
Good stuff. I was actually thinking of getting some Samsung PC3200 for precisely this reason (knowing full well that Samsung and Crucial PC3200 Cas3, for example, are often similar performers to other higher-priced, lower-speced RAM).

Btw, human2k, you might want to just put <quote> stuff</quote> or whatever instead of quoting RaynorWolfcastle's entire post. It makes this page unecessarily long 😉.
 
Interesting to see that all the 400MHz spec memory is rated for 2.6v operation. That makes me think that they are just "factory overclocked," kinda like Intel and AMD raising voltage requirements on higher spec CPUs of the same core.

It is good to see that ± 0.10V as part of the spec. PCB aside, there should then be headroom in the design for running at the maximum (of many overclocker boards) of 2.8v safely.
 
Very nice analysis 🙂 I will be linking this in the hot deals forum everytime someone posts the latest "hot deal" on RAM 🙂
 
Since there are no official specs for DDR400 samsung and others can just change the names on their DDR333 to DDR400. All of the ram is made on the same type of assembly line with the same processes they just pick the better ones to be DDR400.
 
Originally posted by: Lizardman
Since there are no official specs for DDR400 samsung and others can just change the names on their DDR333 to DDR400. All of the ram is made on the same type of assembly line with the same processes they just pick the better ones to be DDR400.
Click to expand...

Intel has specs for DDR400, see the link in my post 🙂
 
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