CAS Fashion Question: Is CAS 8 the new CAS 7?

We’ll start off with Super Pi to check frequency scaling. We set a memory voltage ceiling of 1.85V, which we think is more than most users will ever push into their Hyper based modules for benching. For 24/7 use, we do not suggest more than 1.72V based on conversations with the memory suppliers, actually less is more in this case.

The Corsair modules offer just slightly better voltage/frequency scaling in the Super Pi results. We attribute most of the differences here to the variances in the kits we received. The original Corsair kit actually generated slightly lower results when it came to maximum memory clocks. Our first Blade kit was marginally better when it came to voltages at like settings. The kits tie where the CPU is the limiting factor once we are over 2300MHz with CAS 8-9-8 timings.

Peak gains when using a higher memory bandwidth are certainly apparent between CAS 6 and CAS 7. With the Uncore multiplier at 16X, CAS 6 on the 2:8 memory ratio loses around 10 seconds to CAS 7 running at 2094 MHz with an Uncore multiplier of 20X. In case you’re wondering why there are no Corsair results at CAS 7-7-7 timings, it because out of the six modules we have in the labs, none will post consistently over 1950MHz with CAS 7-7-7 timings at this point. This is irrespective of VDimm settings or swapping the modules around in the slots as we notice early deterioration setting in at this point. In fact, a couple of the modules are already near a 1500MHz limit.

Oddly enough 7-8-7 or 8-9-8 timings still work fine on several of the Corsair modules at 2000, provided we put the module into the right slot to initialize the POST process. This simply comes back to the modules deteriorating through the course of our testing. Our OCZ Blade modules can be plugged in at these timings and still POST although we have started to encounter a few module swap requirements. We are not ruling the board or voltages completely out of the equation just yet, but based upon previous testing results we do not believe the situation is specific to either variance as one of our OCZ modules already failed at stock voltages.

Even a matched Uncore multiplier at CAS 6 is not sufficient to eclipse the CAS 7 2094 MHz 32m time. The Everest results for these 2 test points do confirm the performance advantage of having higher bandwidth and 2ns faster access latency.

Perhaps more interesting than the raw gain versus memory frequency is something we found out during our tests of the EVGA Classified a couple of months ago. The light capacitive load of the Hyper modules allows higher overall processor clocks than memory kits based on Micron or Samsung based parts, reliability issues withstanding of course.

CAS 7 is likely to be the preferred latency setting for most benchmarks, providing enough flexibility for scaling processor clocks right to the limits of the silicon, especially when using locked multiplier CPU’s. Running either set of modules at CAS 8 to around 2250MHz does allow the use of slightly more conservative memory voltage at the cost of the low acess latency of CAS 7-7 timings around 2100MHz. We added a couple of maximum frequency runs above just to show how it all adds up.


Test Setup 3D here we come...
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  • justniz - Wednesday, July 22, 2009 - link

    DONT BUY CORSAIR PRODUCTS.

    Their warranty is a scam and their customer support is insultingly useless.

    I RMA'd $680 worth of memory that was advertised as fully covered with a lifetime waranty. Now they refuse to offer anything other than $90 worth of much lower performing memory. Basically I paid for a Ferrari under lifetime warranty and they will only offer a Daewoo as a replacement.

    All emails to Corsair are either ignored or take days for a response which is mostly just an automated or canned reply that contains no information and is of no actual help. Their customer phone support takes ages to get through, then you speak to someone who hardly speaks English, is technically clueless, and has no authority to make any actual decisions.

    Their phone and email system is designed to completely prevent you from getting to anyone that is actually empowered enough to help you.

    Worst experience ever. I will never buy any Corsair products again.
    My only recourse against them is to share my experience with you, the world, so that you won't make the same mistake I did.

    DONT BUY CORSAIR PRODUCTS.
    Reply
  • BlackDragon24 - Thursday, July 09, 2009 - link

    I'm really glad you took the time to write this article Raja. I went thru two of the top end OCZ blade elpida kits in three days. First kit fried in the first hyperpi32M run only running 1.60 vdimm and 1600 memory speed. Second kit failed after three days while running only 1800mhz with 1.63 vdimm. Third set seems to be running like a champ so far (about 3 months), but I am afraid it won't last long.

    Luckily OCZ was a champ about the whole thing and took care of me very quickly. I would expect as much with $450 memory.

    Hopefully if these fail they'll have a comparable replacement part.
    Reply
  • bobsmith1492 - Wednesday, July 08, 2009 - link

    I would recommend graphing the test results vs. CAS value and clock speed in a 3D graph where CAS is one axis, clock speed is the other axis, and the vertical axis is the test results. That could be a good visual aid to the first block of numbers of test results.

    Other combinations, like processor clock and RAM clock might help also - of course the non-graphed variables would have to remain constant.
    Reply
  • mataichi - Wednesday, July 08, 2009 - link

    I bought some Kingston HyperX T1, and they crapped out after a few weeks. I RMA'd them with Kingston and they said it would be about a month before they had any more in stock.
    Luckily they offered to refund the purchase price, so I took it.
    Reply
  • kitfit1 - Wednesday, July 08, 2009 - link

    Once all the others come into line and "pull" their Elpida as well, the question then is, will they replace ALL the Elpida ram in the wild.
    As no one knows if they have suspect ram (until it dies), the ram company's should do a re-call in the same way that car company's have to do. Then they can replace it with whatever comes after Elpida.
    Reply
  • navilor - Wednesday, July 08, 2009 - link

    According to Corsair:
    http://forum.corsair.com/forums/showthread.php?t=7...">http://forum.corsair.com/forums/showthread.php?t=7...

    We have seen a number of reports across various forums about failures of modules (from Corsair as well as from other memory manufacturers) built with Elpida “Hyper” RAMs. Through lab testing, we have now been able to reproduce similar failures. We are continuing to test to determine the cause of these failures. Note that although a relatively small percentage of “Hyper” ICs appear to be affected, the rate of failure is not acceptable to Corsair or to our customers.

    Due to these failures, we will no longer sell Hyper-based modules until the issue can be resolved. We have also have asked our retailers to return any modules they currently have on their shelves. Products impacted include TW3X4G1600C6GTF, TR3X6G1866C7GTF, TR3X6G2000C8GTF, TR3X3G2000C7GTF, and TR3X6G2000C7GTF. We are working on enhancing our manufacturing and testing process to be able to offer these parts again as soon as possible.

    We continue to stand behind these modules 100% with our standard warranty, which can be found at http://www.corsair.com/warranty/default.aspx">http://www.corsair.com/warranty/default.aspx.
    Reply
  • Rajinder Gill - Wednesday, July 08, 2009 - link

    I think most automobile recalls are due to safety issues more than anything else. We can hope that if there is no such recall here, that the lifetime warranty that OCZ and Corsair offer on these modules will be honored should they happen to fail for users in the future.

    regards
    Raja
    Reply
  • JonnyDough - Wednesday, July 08, 2009 - link

    The price/performance of these modules is so ludicrous that I find myself not even caring...

    Give me half a year and I'll leave your OC'd $5K+ system in the dust for half the price.
    Reply
  • vol7ron - Wednesday, July 08, 2009 - link

    That's because you're not one of the enthusiasts the article was written for. In 6 months, you will not leave a $5K system in the dust for only $2.5K. That's guaranteed.

    Now, if you meant that you could beat a $5K 2009-07-08 system in 2010-01-08 with $2.5K, then that's not really saying anything. In fact, I'm not sure 6 months is enough time these days that it would go down 1/2 price, I would imagine it'd be about 3/4 price in that time and probably a year to turn around; mainly because the bubble for performance enhancement is about to burst.

    Even to say if your statement was true, you could do the same today with half the price of a system 6 mo. prior.

    I guess I'm writing so much about this because I have a problem with your statement in general; especially considering the facts made and context of the article, which you're arguably not the target audience for.
    Reply
  • Dreamwalker - Wednesday, July 08, 2009 - link

    Just read at guru3d.com

    http://www.guru3d.com/news/corsair-pulls-dominator...">http://www.guru3d.com/news/corsair-pulls-dominator...
    Reply

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