As all power users know, quality memory is a must. What is quality memory? Well, for overclockers, having quality memory spec'd to run at overclocked settings is essential in finding that right balance of speed and stability. Once you've established the upper limit, the memory timings are the next steps in tweaking your performance. Quality memory is also about having ram that simply won't crash or riddle your tax program with accounting errors.

There is no shortage of overclocked ram. Despite the JEDEC committee not sanctioning anything past PC2700, those specifications are so mid-2002. Enthusiasts think this, and it's obvious various manufacturers do as well, as they are pumping out PC3000, PC3200, PC3500, and even PC3700 modules like no tomorrow.

It can be argued that these speeds are unnecessary, given that the fastest FSB supported by any CPU (AMD 2700+ and 2800+) right now is 166FSB. At 2.7GB/sec of bandwidth provided by the processor, it isn't enough to saturate the memory at those speeds, and can create problems with latency when the FSB is run asyncronous with the memory clock. Of course, that can be eased by overclocking the CPU, which is the whole point of overclocking fast ram to begin with. You see, you are better off running the ram syncronous with the processor FSB. The reason why faster ram is needed is that vanilla PC2700 will probably run syncronous, anywhere from 166FSB to 190FSB. Even if it can do higher, it likely won't do it at the most agressive memory timings, let alone at PC2700. Our Crucial PC2700, for example, won't do CAS2 at 166FSB, which hurts performance of the system overall.

This brings us back to the original question, what is quality memory? Something that is fast, stable, and reliable. Corsair is one such company that has made quality memory in the past, and today we'll be testing their newest product, the TWINX512-3200LL memory kit.

Specifications

Part Number: TWINX512-3200LL
Speed: 400MHz
Size: 512MB
Organization: 2x32Mx64
Package: 2x184 DIMM
CAS Latency: 2-2-2-6-T1
Memory Type: Twin Modules
RAM Type: 32Mx8

Click to Enlarge

The TWINX is part of Corsair's XMS series, which is their flagship line of products. The sample we've received is the PC3200 (DDR400) 512MB kit, which is 512MB split over two 256MB modules. It's a matched pair, which we will go into more detail about later. There are several models of kits available...

- TWINX512-2700LL: 512 Mbytes, 333 MHz, low latency pair, kit consists of 2 x CMX256A-2700LL DIMMs
- TWINX1024-2700LL: 1 Gbyte, 333 MHz, low latency pair, kit consists of 2 x CMX512-2700LL DIMMs

- TWINX512-3200LL: 512 Mbytes, 400 MHz, low latency pair, kit consists of 2 x CMX256A-3200LL DIMMs
- TWINX1024-3200LL: 1 Gbyte, 400 MHz, low latency pair, kit consists of 2 x CMX512-3200LL DIMMs

Currently, only the nForce2 and KT400 support DDR400, but the ram will work on slower memory buses, such as DDR333. If you're worried about the whole JEDEC specification mentioned earlier, I should point out that Corsair is a member of the committee. You can rest assured that they do follow best business practices, as they've been at this for over 9 years now.

TWINX Dual Channel DDR

One of the big technologies introduced in motherboards recently is dual channel DDR. The nVidia nForce2 has their implementation, as does Intel with their E7205 (Granite Bay). Although they are different platforms, ultimately, they both mean the same thing... two memory controllers working together as one. The idea is that if you use two 256MB sticks of ram, you'll get better performance than one stick of 512MB. Keep in mind that ideally, you'll want both ram modules be of the same size and speed.

As easy as this sounds, you can bet there will always be a curveball or two tossed your way. Like we said, ideally, you'll want two identical sticks. Performance can either be fine, or it can be bad if the sticks are unmatched, as there's no way to tell until you give it a try. In the case where you have the same brand, same size, and same speed memory, there's an outside chance that performance may not be up to par because the 2nd stick was manufacturered while the ram-installing-person was picking their nose.

Corsair tries to take some of the guess work out of the equation for the end user, and does the matching up for you. Here's a quote from their press release...

The TWINX memory kits are composed of two low latency memory modules that have been tested as a pair in an Asus A7N8X dual channel motherboard. The matched pair of modules are then physically packaged together, guaranteeing that the customer receives a product that has been verified in the dual channel environment. These memory kits are available in sizes of both 512 MByte (two 256 MByte modules) and 1 GByte (two 512 MByte modules), at speeds of either 333 MHz (also known as PC2700) or 400 MHz (also known as PC3200).

The ram is essentially the same as that reviewed by David some time ago. The difference of course is that there are two sticks in this kit, pre-tested in a dual channel environment. Individually, both modules are 256MB, rated at 400MHz.

Given the high speed capabilities of the ram, like all Corsair modules, they slap on aluminum heatsinks to keep the ram cool. They look pretty sharp... decorated with the white on black logo, as well as a silver hologram displaying the memory model.

It's pretty tough to tell without tearing them off, but the modules are not attached to the heatspreaders by thermal epoxy, but rather by some frag tape. The tape is one long strip, going from one end of the module to the other. It's arguable whether or not ramsinks drastically lower temperatures to a point where it makes a difference in overclocking, but I suppose some (cooling) is better than none.

Although the TwinX Kit is rated at 400MHz, contrary to popular belief, the speed of the ram is not the single most important factor when shopping for ram. Yes, it is important, but you should also pay attention to latency. Fact is, running ram at 433MHz at conservative timings will not be as fast as 400MHz with aggressive timings.

The numbers, outside of the MHz value that will be of interest to you are those found to the very right (pictured above). The numbers you see are 2-2-2-6-Ti, which in order refer to the CAS latency, the RAS precharge, the RAS-to-CAS delay, RAS active to precharge, and command rate. I'm not going to go too deeply into the various definitions, but you can grab some info from Corsair's site if you need a refresher. All you have to know is the lower the numbers, the better.

Another thing you have to know is that Corsair configured the Serial Presence Detect (SPD) for the TwinX at the above speed ratings. What this means that your motherboard should automatically detect the specifications set forth by Corsair for this kit. You can always do some tweaking, but it's nice to know that Corsair already did what they felt they needed to to get your memory installation as optimized as possible, as well as being confident that the memory will also perform as advertised.

Overclocking

The first test was to see if we could run the TWINX at its rated 400MHz, 2-2-2-6-T1 settings. This is always a good first step just to make sure your ram is working as it should be.

With such aggressive timings, I then moved the DDR speeds upwards, 1MHz at a time until we reached our maximum overclock. As we approached the higher speeds, stability was a concern, and we've had to increase the memory voltage up 2.8v to maintain stability. At 2-2-2-6, we managed a maximum overclock of 221MHz (442MHz DDR). Needless to say, we got some impressive SiSoft memory benchmarks, but the ram would consistently fail the Memtest86 tests. Clocking back down to 217MHz (434MHz DDR) resolved those issues.

The next overclocking test was to determine the maximum overclock with 2-2-2-5 timings. As with the previous tests, we needed to up the voltage again to 2.8v. With such aggressive timings, as expected, our overclocking results wavered a little. 400MHz, 2-2-2-5 was a success, but we only got up to 211MHz (422MHz DDR) before the system started to crash. At 211MHz, the system was rock solid, passing the Memtests86's tests with flying colours.

The last test was to determine the absolute highest overclock. We had varying levels of success, but we needed to move away from our aggressive timings. We adjusted our timings to a more conservative 2.5-2-2-7, increased the voltage to 2.8v.

A 226MHz (452MHz DDR) was the best we were able to manage while still maintaining stability. I did try the same overclock again, and lowered the ram back to CAS2, but while it got to the Windows logon screen, the PC just froze there.

Therefore, in summary, here's our results of our best, and most stable, overclocks:

	2-2-2-5	2-2-2-6	2.5-2-2-7
Corsair TwinX	211MHz (422DDR)	217MHz (434DDR)	226MHz (452DDR)

Test Setup

Epox 8RDA+ nForce2: Athlon XP 2400+ (12x166: 1192MHz) provided by HighSpeed PC, 2 x 256MB Corsair TwinX Ram, ATi Radeon 9700 Pro, 120GB Western Digital SE 8MB Cache, Windows XP SP1, nForce 2 Unified Driver Package 2.0, ATi Catalyst 3.0

Test software will be:

SiSoft Sandra 2003
PC Mark 2002 Memory
PiFast
Quake 3
3D Mark 2001 SE
UT2003

We'll be presenting benchmarks at both the ram's stock speed (400MHz), as well as at the overclocked speeds, with the timings as shown earlier this page. Tests were done with the FSB and memory speed syncronous @ 166 (333DDR, 2-2-2-6), and asyncronous for 200MHz (400DDR) and up.

SiSoftware Sandra 2003

Although a synthetic benchmark, it's a popular one, freely available if you wish to make comparison benchmarks. We will be testing the memory speeds.

PC Mark 2002 - Memory

This is one synthetic benchmark that we here at VL don't exactly put a lot of emphasis on, but we're aware that many of our readers do use it.

As we should expect, memory performance increases with each overclock. Although the CAS latency had to be bumped up to 2.5, the best performance was at 226MHz (452FSB). Keep in mind that both SiSoft and PC Mark are not real world benchmarks, but they do give a scale in which to measure against.