With a good overclocking Pentium 4 2.4C, you can crank your bus up to 250 (1000 FSB) and enjoy 3.0GHz performance with the entry level Northwood. The manufacturers of enthusiast memory noticed what was going on and quickly filled the void with DDR500 memory. Until recently, DDR533 was the fastest memory you could buy, but now Corsair and OCZ have introduced PC4400, which can run at a heady DDR550.

You would be right to ask at what price you get DDR550 performance, because Corsair and OCZ both specify a very limited group of motherboards that can support this speed. Both list the Asus P4C800-E and Deluxe as compatible, and OCZ adds the DFI LAN Party 875B. That's it - only two recommended compatible motherboards for the fastest memory speed that you can buy. In addition, both specify timings as 3-4-4-8, which means speed is achieved with slower memory timings.

So, the question is, do the two new PC4400 memories meet their specifications and actually perform at DDR550? Are the trade-offs worth it? Is DDR550 a product that actually brings additional performance to the table, or are they just check list products to persuade the consumer the company markets the fastest memory that you can buy?

Why Would Anyone Want DDR550?

When computer users visit some of the hard-core Enthusiast sites on the web, one of the first things that they will likely see is memory overclocking. You will see dropped multipliers and incredible FSB settings, all in the effort to raise the memory speed to the highest level possible. Skeptics always ask, why all the fuss? What do you really gain?

3.2GHz CPU Speed, Different FSB and Memory Speed

To try to answer that question, we took a close look at our 3.2ES. The unlocked CPU allows multipliers to be selected from 12 to 16, which means with DDR550 memory, we should be able to compare 3.2GHz performance at two very different settings. At a multiplier of 12 and a bus setting of 266 (DDR533), we can achieve 3.2GHz. This can also be achieved at 16x200 (DDR400) with a default 3.2 Pentium 4. So how does performance compare at the same 3.2GHz?

3.2GHz Performance - Different FSB - Corsair XMS4400
Memory Speed & Multiplier	Memory Timings & Voltage	Quake3 fps	Sandra UNBuffered	Sandra Standard Buffered	Super PI 2M places (time in sec)	Halo DX9 1024x768	Comanche 4 1024x768
400DDR 16x200	2-3-3-7 2.55V	378.5	INT 2624 FLT 2680	INT 4528 FLT 4527	108	54.9	60.25
533DDR 12x266	2.5-4-4-7 2.75V	411.9	INT 3345 FLT 3362	INT 5842 FLT 5819	102	55.2	63.25
% Change		+8.8	+26.5	+28.8	-5.6	+0.6	+5.0

At the exact same CPU speed, lowering the multiplier and increasing the bus setting and memory speed increases performance 26% to 28% in Memory. This translates to improvements in gaming performance from only 0.6% in Video-Card/CPU bound games like Halo to 8.8% in Quake 3. Keep in mind that the CPU speed is exactly the same, only the bus speed has been increased. This is what the overclockers are aiming for, at even more extreme levels than we have tested here.

In this example, there is an ongoing argument as to which really contributes to the increased performance. Some believe that the increase in the FSB to the CPU is mainly responsible for the improved performance on Intel 875/865 boards. They argue that a high FSB combined with slower memory at aggressive timings will give the exact same results. We decided to test that argument with the fastest DDR400-433 memory we have compared to this Corsair XMS 4400 at DDR533.

3.2GHz CPU Speed and Same 533 FSB, 1:1 Memory vs. 5:4 Memory

To test this claim, benchmarks were run at the same 3.2GHz CPU speed achieved with the same 12x533 multipliers. This means that the FSB was a constant 1066 in these tests. Memory was tested at DDR533 with slower timings and compared to another memory at DDR 426 (5:4) at the fastest timings available of 2-2-2-6.

3.2GHz & 1066 FSB - 1:1 Memory vs. 5:4 Memory
Memory Speed & Multiplier	Memory Timings & Voltage	Quake3 fps	Sandra UNBuffered	Sandra Standard Buffered	Super PI 2M places (time in sec)	Halo DX9 1024x768	Comanche 4 1024x768
426DDR 5:4 12x266	2-2-2-6 2.65V	412.3	INT 3061 FLT 3116	INT 5678 FLT 5695	101	55.35	63.49
533DDR 12x266	2.5-4-4-7 2.75V	411.9	INT 3345 FLT 3362	INT 5842 FLT 5819	102	55.2	63.25
% Change		0	+8.6	+2.5	-1.0	-0.3	-0.4

The results for 1:1 with slower timings versus 5:4 with fastest timings are very interesting. While synthetic memory tests like Sandra show 1:1 memory 2.5% to 8.6% faster, all the games perform essentially the same to slightly faster with the slower memory at 5:4 with faster timings. This pretty much destroys the arguments made on some sites that memory timings do not matter in high-speed memory. If Memory timings did not matter, then DDR423 would certainly perform much slower than DDR533, when in fact DDR423 is the same to faster.

In fairness, no one would argue that DDR550 at 2-2-2-6 is no faster than DDR400 at 2-2-2-6. All things being equal, faster speed will be faster. With today's memory, however, all things are not equal, and we are often forced to use slower timings as a trade-off for faster 1:1 memory speeds. Sometimes the trade-off is not worth it, and you are better off with slower memory running at 5:4 with the fastest timings possible. Do you save money with this approach? Not really, since the best DDR400 to DDR433 memory that will actually run at 2-2-2-6 timings is about as expensive as the faster memory with more relaxed timings. If you already own very fast DDR400 to 433 memory, however, 5:4 may be just as good an option as high speed memory with slower timings.

The Verdict

Faster memory running at higher speeds can clearly provide better performance, but there is no clear answer as to whether you need DDR550 memory. The market itself is very limited at present with only one or two motherboards recommended as capable of running DDR550. If you own a motherboard and CPU capable of running at DDR550 (275 setting), then DDR550 is an option. Keep in mind, however, that memory can run at slower speeds, and the performance of DDR550 in the range of DDR400 to DDR550 should be weighed in your decision.

Corsair XMS4400 1GB TwinX

Corsair was the first to bring DDR550 or PC4400 to market.

The Corsair DDR550 tested is a matched pair of 512MB. Corsair calls their matched pairs for Dual-Channel TwinX. Our flavor had the black heatspreader, but Corsair also provides 4400 TwinX with Platinum spreaders if you prefer that.

Corsair XMS4400 TwinX Specifications

Corsair XMS4400 v1.1 Memory Specifications
Number of DIMMs & Banks	2 DS
DIMM Size Total Memory	512 Mb 1 GB
Rated Timings	3-4-4-8
Rated Voltage	2.75V

We confirmed the SPD timings to be set at 3-4-4-8. Corsair states on their site that all PC4400 is tested on an Asus P4C800-E motherboard before packaging. The Asus P4C800 is the only motherboard recommended by Corsair for DDR550 operation with this memory.

Normally, we remove heat-spreaders and report the memory chips used, but Corsair must be attaching the heatspreader with epoxy these days. While we could not confirm the chips used by examining them, they behave like Hynix chips, though we do not know whether Corsair uses D43 or C-D5 blanks. This is speculation on our part, but there are very few memory manufacturers that produce high-speed memory.

OCZ PC4400 Dual-Channel Kit

OCZ also provides a matched pair of 512MB DIMMs in their Dual-Channel Kit.

OCZ packaging is virtually identical to Corsair packaging. The OCZ website calls the matched pairs "Dual-Channel Kits". Heatspreaders on the OCZ PC4400 were copper-colored.

OCZ PC4400 Dual-Channel Kit Specifications

OCZ PC4400 Dual-Channel Kit Memory Specifications
Number of DIMMs & Banks	2 DS
DIMM Size Total Memory	512 Mb 1 GB
Rated Timings	3-4-4-8
Rated Voltage	2.70V

We confirmed that the SPD timings to be set at 3-4-4-8 at DDR550. OCZ states that the DDR550 parts are tested to work with the Asus P4C800 or the DFI LAN Party 875B. Testing is performed on an Asus P4C800 motherboard before packaging. For DDR550 memory, OCZ is using Hynix Revision C-D5 memory chips.

Performance Test Configuration

The Memory testbed for evaluating the Corsair XMS4400v1.1 and OCZ PC4400 is the same used in our earlier reviews of DDR500 and other High-Speed Memory.

OCZ PC3700 Gold Rev. 2: The Universal Soldier
OCZ 4200EL: Tops in Memory Performance
Mushkin PC4000 High Performance: DDR500 PLUS
Corsair TwinX1024-4000 PRO: Improving DDR500 Performance
Mushkin & Adata: 2 for the Fast-Timings Lane
Searching for the Memory Holy Grail - Part 2

All test conditions were as close as possible to those in our earlier memory reviews.

INTEL 875P Performance Test Configuration
Processor(s):	Intel Pentium 4 2.4GHz (800MHz FSB)
RAM:	2 x 512MB Corsair XMS4400v1.1 TwinX (DS) 2 x 512MB OCZ PC4400 DC Kit (DS) 2 x 512MB OCZ PC3700 Gold Rev. 2 (DS) 2 x 512MB OCZ 4200EL(DS) 2 x 512MB Mushkin PC4000 High Performance (DS) 2 x 512MB Corsair TwinX4000 PRO (DS) 2 x 512MB Mushkin Level II PC3500 (DS) 2 x 256MB Adata DDR450 (SS) 2 x 512MB Adata PC4000 (DS) 2 x 512MB Corsair PC4000 (DS) 2 x 512MB Geil PC4000 (DS) 4 x 256MB Kingston PC4000 (SS) 2 x 256MB Kingston PC4000 (SS) 2 x 512MB OCZ PC4000 (DS) 4 x 256MB OCZ PC3700 GOLD (DS)
Hard Drives	2 Western Digital Raptor Serial ATA 36.7GB 10,000 rpm drives in an Intel ICH5R RAID configuration
PCI/AGP Speed	Fixed at 33/66
Bus Master Drivers:	875P Intel INF Update v5.00.1012, SATA RAID drivers installed, but IAA not installed
Video Card(s):	ATI 9800 PRO 128MB, 128MB aperture, 1024x768x32
Video Drivers:	ATI Catalyst 4.1
Power Supply:	Vantec Stealth 470Watt Aluminum
Operating System(s):	Windows XP Professional SP1
Motherboards:	Asus P4C800-E (875) with 1015 Release BIOS

Since both Corsair and OCZ target their DDR550 memory at the Intel 875/865 enthusiast, we only tested on our Intel test bed.

Test Settings

The following settings were tested with Corsair XMS4400v1.1 and OCZ PC4400:

1. 800FSB/DDR400 - the highest stock speed supported on 875/865 motherboards.
2. 1000FSB/DDR500 - the specified rating of the majority of recent memory modules that we have tested.
3. 1066FSB/DDR533 - the maximum speed that many current Intel 865/875 boards can achieve. This value was also tested because it provides 3.2GHz speed at 12x266, which is a useful comparison to standard Intel 3.2GHz performance.
4. 1100FSB/DDR550 - the specified rating of the test memory modules.
5. Highest Stable Overclock - the highest settings we could achieve with this memory and other memory we have tested.

These are the same settings used in benchmarking other memory in the above list of memory tests, except for the addition of a 533 value for comparison.

Test Results: Corsair XMS4400 & OCZ PC4400

To test overclocked stability, we used the very demanding Gun Metal 2 - Benchmark 2, which pushes systems with its DX9 routines. To be considered stable for test purposes, Gun Metal, our Quake3 benchmark, UT2003 Demo, Super PI, Halo, and Comanche 4 had to complete without incident. Any of these, and in particular Super PI and Gun Metal, will crash a less-than stable memory configuration.

Corsair XMS4400v1.1 TwinX - 2 x 512Mb Double-Bank
Speed	Memory Timings & Voltage	Quake3 fps	Sandra UNBuffered	Sandra Standard Buffered	Super PI 2M places (time in sec)
400DDR 800FSB	2-3-3-7 2.55V	318.1	INT 2663 FLT 2639	INT 4442 FLT 4445	133
500DDR 1000FSB	2.5-3-4-7 2.65V	390.2	INT 3147 FLT 3228	INT 5549 FLT 5520	108
533DDR 1066FSB	2.5-4-4-7 2.75V	411.9	INT 3345 FLT 3362	INT 5842 FLT 5819	102
550DDR 1100FSB	3-3-4-8 2.75V	422.9	INT 3415 FLT 3529	INT 6054 FLT 6008	98
560DDR 1120FSB	3-3-4-8 2.75V	436.8	INT 3606 FLT 3538	INT 6124 FLT 6101	95

Corsair XMS4400 did not perform any better or reach higher overclocks when using 2.85V for the memory. In fact, performance was often worse or we got a no-boot condition when 2.85V was selected. 2.75V allowed us to get all we could from Corsair's DDR550.

OCZ PC4400 Dual-Channel Kit - 2 x 512Mb Double-Bank
Speed	Memory Timings & Voltage	Quake3 fps	Sandra UNBuffered	Sandra Standard Buffered	Super PI 2M places (time in sec)
400DDR 800FSB	2-3-3-7 2.55V	319.3	INT 2686 FLT 2653	INT 4455 FLT 4422	133
500DDR 1000FSB	2.5-3-4-7 2.65V	387.7	INT 3146 FLT 3246	INT 5516 FLT 5470	108
533DDR 1066FSB	3-3-4-7 2.75V	412.2	INT 3416 FLT 3450	INT 5846 FLT 5888	102
550DDR 1100FSB	3-3-4-8 2.75V	421.9	INT 3446 FLT 3518	INT 6040 FLT 6003	98
571DDR 1142FSB	3-3-4-8 2.75V	438.5	INT 3752 FLT 3642	INT 6231 FLT 6237	94

OCZ PC4400 reached approximately the same overclock at 2.75V that we found with Corsair's DDR550. That is, both reached about DDR560 at 2.75V. The OCZ did not have a problem with 2.85V, however, and continued on to 571DDR. Frankly, neither of these results with DDR550 shows much headroom. 560 and 571 represent just 1.8% to 3.8% over the DDR550 specification. This is much less "reserve" than we normally see with Premium memory.

Performance Comparisons

Performance of the Corsair and OCZ DDR550 was compared to all of the memory recently tested in:

OCZ PC3700 Gold Rev. 2: The Universal Soldier
OCZ 4200EL: Tops in Memory Performance
Mushkin PC4000 High Performance: DDR500 PLUS
Corsair TwinX1024-4000 PRO: Improving DDR500 Performance
Mushkin & Adata: 2 for the Fast-Timings Lane Searching for the Memory Holy Grail - Part 2

Memory performance was compared at DDR400, DDR500 and the highest stable overclock we could achieve that would run Gun Metal 2 Benchmark 2, Quake 3, UT2003, and Super PI to 2MM places. Where the data was available, comparisons were also made at DDR533 and DDR550 - the rated performance of PC4400 memory.

Results are compared for Quake 3, Sandra UNBufferred Memory Test, and Super PI. The SiSoft Sandra reports 2 results for each memory test - an Integer value and a Float value. Results reported in our charts are the result of averaging the INT and FLOAT scores, which are normally close in value. INT and FLOAT scores were added and divided by 2 for our reported score.

DDR400 Results

DDR500 Results

DDR533 Results

DDR550 Results

Highest Memory Speed Results

Final Words

Corsair XMS4400 and OCZ PC4400 both perform as specified at their rated speed of DDR550. This makes these the highest rated memory that we have tested at AnandTech. Both also equal old records or reach new highs in memory speed at DDR560 to DDR571. While the OCZ reaches further than Corsair's DDR550, performance across the curve is very similar and the memory performance is, in most cases, so close that it is hard to choose one over the other. In Quake 3, though, OCZ PC4400 managed to set a new performance record.

It should also be mentioned that both memories were exceptionally stable to about DDR533-540, but neither were particularly outstanding in stability at the highest speeds. It was also interesting that the gains above DDR533 were pretty small. This could have been the fault of other system components, but since all testing was done on the recommended Asus P4C800-E, there is no place left to go. We do believe that the 10,000 RPM SATA RAID may be compromising stability at some of the highest memory speeds despite the PCI/AGP lock on Intel's current chipsets.

While it's true that these two DDR550 memories reach new high speeds in our performance tests, it is not to say that they are the fastest memory we have tested. Performance is much more than a speed setting and the lower timings required to reach these higher speeds took their toll on performance. Compared to OCZ 4200EL and Corsair XMS4000 PRO, the performance at the same speed was slower with the timings required for DDR550. At the other end of the scale, we also saw slower DDR423 with 2-2-2-6 timings meet or best DDR533 performance with the slower timings required for DDR550.

The fastest memory that we have tested thus far is the truly excellent OCZ 4200EL. It remains #1 in most of our benchmarks, and it is still the best high-speed memory that we have tested. Corsair XMS4000 PRO and Mushkin 4000 High Performance perform just as well as OCZ 4200EL, but their range is not quite as wide as the incredible DDR400 to DDR560 that we found with OCZ4200EL. If we were in the market for high-speed memory, we would choose one of these 3 memories over either Corsair XMS4400 or OCZ PC4400.

In the end, Corsair XMS4400 exceeded its specifications and performs very well at DDR550, which is an incredible bus speed of 1100MHz or 1.1GHz. OCZ PC4400 performed about the same throughout the range, but reached an even higher maximum overclock. Both of these DDR550 memories perform as promised. However, the fastest high-speed memory overall is still OCZ 4200EL, with Corsair XMS4200 PRO and Mushkin 4000 High Performance very close in performance.

We all want DDR500 that can run at 2-2-2-6 timings, but until that becomes a reality, memory like OCZ 4200EL, Corsair XMS4000 PRO, and Mushkin 4000 High Performance provide excellent speed and decent timings. If top-speed at any cost is your goal, then XMS4400 or OCS PC4400 will let you reach new highs in memory speed at voltages that won't fry your board.

After the reach to new highs, it seems all the companies that specialize in memory for the Computer Enthusiast have recently announced faster DDR400 memory. Considering how well very fast DDR400-433 performs compared to high-speed memory at slower timings, we understand why this is a hot topic again. Our next look at memory will examine performance of some of the latest, faster DDR400.