OCZ DDR2 PC2-9200 FlexXLC expands DDR2 Boundaries

Memory by thorgal @ 2007-01-23

The last few months have been rather turbulent in memory land. Several new modules have been introduced to the market, some of which are quite revolutionary. Of course, OCZ could not fall behind, and has introduced a new top end memory module with a totally new design, and we spent some quality time with it, can it beat our reigning overclocking champ?

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Test setup and Overclocking Results

Test setup

Let's have a look at our test setup, which we use for all our memory reviews on the Intel side of things:

Test Setup

Madshrimps (c)
CPU Intel E6700 Core 2 Duo
Cooled by Tuniq Tower 120
Mainboard Asus P5B-Deluxe/wifi AP (modded)
Memory 2x 1Gb Generic PC4300 Ram (4-4-4-15)
2x 1Gb OCZ PC9200 FlexXLC
2x 1Gb OCZ PC6400 Special Ops Edition Urban Elite
2x 1Gb Mushkin PC8000 Redline
2x 1Gb OCZ PC8500Pt SLI/EPP
2x 1Gb Team Group PC6400 "333"
2x 1Gb Corsair Dominator PC8888C4
Sapphire X1950XTX
LG DVD-rom drive
Wester Digital Raptor WD800 SATA
OCZ GameXstream 700 Watt PSU

As we explained in our previous reviews, the "Generic PC4300" module is a 533Mhz part with quite basic timings, at the time of writing. This "Generic" module does not really exist: we constructed this module with the Corsair Dominator modules, but slowed the modules down to 533 Mhz DDR with (relatively) slow timings. The timings we "arranged" are 4-4-4-15 timings. You might wonder why we chose exactly this speed and these timings. We could have picked an even slower part with PC3200 speeds or 5-5-5 timings, but than again, these modules are barely available anymore. The cheapest memory kits you can find nowadays are almost all capable of doing 533Mhz with 4-4-4 timings, so in our opinion, this seemed like a nice performance base to compare our memory kits with.

Test methodology

Every module we test, except for the above mentioned generic module, was put to the test at five different speeds:

  • PC6400 - 800Mhz performance, at the best possible timings
  • PC8500 - 1066Mhz performance, at the best possible timings*
  • Maximum cas 3 performance
  • Maximum cas 4 performance
  • Maximum cas 5 performance

    *1066 Mhz is tested only for the modules for which this is possible, in this case all the modules were capable of reaching this speed, except for the PC6400 Urban Elite, which is omitted in that table.

    For the 800Mhz and 1066Mhz tests, settings are very simple: in bios only the memory speed was turned up to the appropriate setting, while front side bus (FSB) and cpu speed (and multiplier) remained at the stock settings of 266FSB and 2.66Ghz respectively.

    The maximum cas "x" performance is measured at other than stock cpu and FSB settings, to be able to give the memory sufficient bandwidth, and to play down the influence of the cpu in comparison to the memory. In our tables on page 8 you'll see that the cpu speeds and FSB setting is always mentioned at the bottom, so please bare that in mind when comparing the results. So to be clear: results cannot be directly compared, as the cpu/Fsb factor accounts for a certain % of the performance shown.

    For the cas 3 setting we test with a CPU multiplier of 9, and a memory divider of 4:5 or 667Mhz in bios. For the cas 4 and 5 setting we test with an CPU multiplier of 8, and a memory divider of 2:3 or 800Mhz.

    A word on Asus P5B-deluxe performance

    The motherboard that we are using for all our memory testing is the Asus P5B deluxe/wifi-AP, a motherboard equipped with the Intel 965 chipset. We chose specifically this motherboard because it is capable of attaining very high front side bus speeds compared to motherboards equipped with the Intel 975 or (older) nVidia chipsets. Among the 965 motherboards, the Asus is also one of the better performing boards, often reaching FSB speeds of more than 500FSB. Of course, when we want to test memory overclocking, we need a motherboard that is capable of this high FSB, and one that is compatible with high frequency ram (the 975 chipset is known to give problems with ram over 1000Mhz, sometimes).

    Over the last couple of months, many of the highly respected memory guru's, with Tony Bigtoe and Freecableguy (FCG) on the forefront, have been looking for answers where this high FSB performance, and consequently the high memory performance, was coming from on the P965 chipset. At a certain moment, maximum memory speeds were all of a sudden booming all over the internet, and the general feeling was that some "impossible" memory scores were floating around. That's why some answers had to be found.

    You must realize that, when you start pumping up the FSB of your motherboard, you are actually overclocking your chipset. Just like memory, chipsets have standard timings and standard voltages, and when you're overclocking you can give a little more voltage to the chipset, in order to make it scale higher. Normally, once you hit 380-430FSB on the Intel 965 and the 975 chipset, you hit an overclocking wall (unless you do some more exotic, warranty voiding trickery of course...) . How does Asus reach 500FSB than ? One of the things Tony found out was that the P5B automatically relaxes (slows down) the timings of the chipset itself in order to be able to scale above 400FSB. There seem to be certain "sets" of timings which are implemented at different FSB settings, and these sets are called "straps". The Asus P5B now sets a different strap when you boot at 400+FSB, than when you boot at 400-FSB, the 400+ strap being the slower of the two. This obviously has a direct influence on your memory bandwidth and on the entire performance of your PC. This will show up in this review as well, when we're looking into the performance of the Team Group's ram, which scaled beyond 400FSB on our settings, and in the process gives worse results than you would actually expect... To conclude: some answers were found already, but others remain unanswered for the time being. Tony and the others are still working very hard to unravel more mysteries, and try to get the motherboard manufacturers on board in the process.

    Take a look at this and this thread by Tony Bigtoe over at the OCZ support forums of BleedinEdge, and also at this thread at the XtremeSystems forums. Finally, here's a link to Tony's P5B-deluxe tweaking guide, from the excellent Tech Repository forums which have been recently founded by Kris "FCG" and Tony "Bigtoe". These threads are in my personal opinion obligated reading for anyone considering to buy a top performing memory kit, just to understand the performance of your PC setup.

    Overclocking performance

    The goal of this section of the review is to look how far the modules are willing to go. For this we played around with different memory latencies a bit, to end up with the best cas 3, cas 4 and cas 5 performance of these particular modules.

    In our experience, Orthos is the most demanding stability test we can run. Orthos is the dual core version of the better known Stress Prime 2004, or SP2004 in short. Even when all tests succeeded, Orthos testing would sometimes fail. On the other hand, when Orthos succeeded in running for about 1/2 hour, other tests would (almost) never become a problem.

    As the specifications on the previous pages pointed out, the FlexXLC kit is rated to work at speeds of PC2-9200 or 1150Mhz DDR2, and this with 5-5-5-18 timings and at a voltage of 2.35V. For the testing of OC performance, we never exceed the warranted voltages, so in this case we applied voltages up to 2.5V. For your information, 2.5V is not supported by the Asus P5B-deluxe by default; a voltmod was applied to the motherboard in order to supply these voltages. The memory voltages were also monitored by a multimeter in order to verify that they are accurate when testing.

    Let's start with these rated timings, and see how far the modules can be overclocked at a cas setting of 5 cycles.

    To cut through the chase immediately: performance was nothing short of stellar! Whereas our previous champion, the Team Group Xtreem PC6400 reached an already astonishing 1218Mhz, the OCZ PC9200 just blew them away : we're very pleased to announce that the OCZ PC9200 FlexXLC was able to get up to 1280Mhz DDR on the standard timings, a more than 11% overclock over the stock speeds which are extreme already ! Furthermore, we also found that the TRP latency could be tightened a little bit : the memory also reached 1280Mhz with 5-5-4-18 timings. The voltage at which the modules reached this setting was 2.5V, nicely within warranty. This would mean these modules can get the speed rating of PC2-10200 already!

    Next up is the cas 4 setting, where the performance was a little less impressive, but still very good : the PC9200 reached a speed of 1093Mhz with 4-4-4-18 (CAS-TRCD-TRP-TRAS) timings. This was still within the warranted voltage of 2.5V. The performance at cas 4 falls a little short in comparison with the other high end PC8000+ memory we tested thus far, but then again : this memory is clearly tuned for cas 5 performance...

    Tony has let me know that cas 4 overclock headroom could be expanded by altering the subtimings a little. One subtiming you should definitely have a look at is the "write to precharge delay" latency, which on the P5B has a standard bios setting of 10 cycles, but could use an increase to 11 cycles, and for some even up to 13 cycles. In my personal experience this didn't make a lot of difference, but you could try this anyway...

    Finally, at the cas 3 setting, the PC9200 reached 820Mhz setting at timings of 3-4-3-15, 2.5V. My memory set didn't like a TRCD setting of 3 cycles very much, but your mileage may vary (as with all overclock results).
    In the (near) future I'll retest the memory with the 680i chipset, which should theoretically give some better cas 3 and 4 results : it's possible that my P5B just doesn't like these settings very much... To make a long story short : I suggest you use these modules with the cas 5 setting : you definitely won't regret it !

    Before we go on to the benchmark results, one more thing. An additional drawback of the cas 3 and cas 4 settings is that my P5B motherboard refused to cold boot with these settings applied. When powering up the rig, I first had to change sticks, apply the correct cas 3 or cas 4 setting (together with the correct memory voltage) with some other memory I had lying around, power down, and change back to the PC9200... After that, the memory got back to work most of the time without further ado. I did not experience this behavior with cas 5 or SPD performance, but if these are going to be your only memory sticks, you should be aware of this drawback. Last week I did get a message from Tony in which he stated that a solution for this problem is in the making, so I am looking forward to that.

    Below are the screenshots of the Orthos runs at the maximum memory speeds we achieved, for the different cas and system settings.

    Madshrimps (c) Madshrimps (c) Madshrimps (c)

    Left to right (click to open) : Maximum CAS3, CAS4, CAS5

    On to the benchmark results now ->
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    Comment from SuAside @ 2007/01/24
    DDR2 promised us low power use & lower heat specs

    now we've got DDR2 with not only huge heatsinks à la Corsair, but with stock watercooling ^^
    Comment from jmke @ 2007/01/24
    time for DDR3
    Comment from thorgal @ 2007/01/24
    Originally Posted by SuAside View Post
    DDR2 promised us low power use & lower heat specs

    now we've got DDR2 with not only huge heatsinks * la Corsair, but with stock watercooling ^^
    It's all micron's fault

    No seriously, as long as there are enthusiasts, memory will be built to exceed JEDEC specs. THe same will be true for DDR3 imho.
    Comment from Rutar @ 2007/01/24
    I think Core 2 is to blame, if we could use lower dividers we wouldn't need such high frequency memory for overclocking,
    Comment from jmke @ 2007/01/24
    I can push my mainboard way beyond spec FSB wise without even reaching rated PC2-6400 speed...divider options on 975 chipset are sufficient;
    Comment from SuAside @ 2007/01/24
    Originally Posted by thorgal View Post
    No seriously, as long as there are enthusiasts, memory will be built to exceed JEDEC specs. THe same will be true for DDR3 imho.
    of course, but usually that's also a sign that the next generation of technology should be ready for release soon (or there'll be trouble )

    Originally Posted by jmke View Post
    I can push my mainboard way beyond spec FSB wise without even reaching rated PC2-6400 speed...divider options on 975 chipset are sufficient;
    well, solo my memory goes well over the 6400 speeds and so does the CPU, but cant get it over 400 in 1:1.

    but that has nothing to do with divider options, of course.