DDR2 vs. DDR: Revenge Gained

DDR2 memory tests, which we have performed earlier, showed that its higher latency is exactly the reason why it gets defeated by the regular DDR SDRAM. However, now the situation is changing. The leading memory manufacturers offer DDR2 modules with improved timings, which make DDR2 look completely different from what it used to be.

by Ilya Gavrichenkov
12/17/2004 | 01:46 PM

New technologies emerging in the computer market are but seldom unanimously accepted by the public. Some time is always necessary as an adaptation period during which the users are grieving over the good old past and the bad new present while the manufacturers are improving the parameters of their new products. Intel’s LGA775 platform began its market life by the same scenario.

 

As we showed in several test sessions, the new platform didn’t provide any performance advantages in comparison to ordinary Socket 478 systems if you used CPUs of the same frequency. Why? The chipsets employed in LGA775 systems were oriented on the new memory type, DDR2 SDRAM, and this new memory used to be slower than DDR SDRAM. This made some PC enthusiasts and advanced users spurn systems based on Intel’s i915 and i925 chipsets as slow, compared to the time-tested i875/i865 chipsets. The new graphics bus, PCI Express x16, implemented in Intel’s new-generation chipsets couldn’t save the day, either.

Yes, it was theoretically better, providing a much higher bandwidth, but you couldn’t feel that in practice as graphics cards with the AGP 8x interface are not inferior to their PCI Express x16 analogs.

Intel and the numerous manufacturers of mainboards and graphics cards are overall putting much effort into pushing the users towards the new platform. Particularly, all new and speedy Pentium 4 models are announced for the LGA775 platform only, and the graphics card makers are also releasing new products in the PCI Express x16 variant. Yet, these two arguments are not enough to win the hearts of the users. Many applications demand a high memory performance, and DDR2 SDRAM employed in LGA775 platform just couldn’t provide it.

It couldn’t but it can now! We’ve been scolding DDR2 SDRAM for being slower than ordinary DDR memory, but this article is going to show you that DDR2 SDRAM can be faster than its predecessor!

DDR2: Theoretical Basics

To understand the advantages and shortcomings of DDR2 SDRAM in comparison to DDR SDRAM we should learn some basic facts about its architecture. First of all, you should be aware that DDR2 memory is fundamentally similar to DDR SDRAM. Still, while DDR SDRAM can transfer data across the bus two times per clock, DDR2 SDRAM can perform four transfers per clock. DDR2 uses the same memory cells, but doubles the bandwidth by using the multiplexing technique.

The DDR2 memory cell is still clocked at the same frequency as DDR SDRAM and SDRAM cells, but the frequency of the input/output buffers is higher with DDR2 SDRAM. The bus that connects the memory cells with the buffers is twice wider compared to DDR. Thus, the I/O buffers perform multiplexing: the data is coming in from the memory cells along a wide bus and is going out of the buffers on a bus of the same width as in DDR SDRAM, but of a twice bigger frequency. This allows to increase the memory bandwidth without increasing the operational frequency of the memory cells (the DDR2-533 cell works at the same frequency as a DDR266 SDRAM or a PC133 SDRAM cell, and the transition from DDR SDRAM to DDR2 SDRAM resembles much the transition from SDR SDRAM to DDR SDRAM). Still, this simple method of increasing the memory bandwidth has its downsides, too. The main disadvantage is high latency. The memory latency does not depend on the frequency of the I/O buffers or on the width of the bus the data are coming in from the memory cells. The main factor affecting the latency is the latency of the memory cells themselves. The latency of DDR2-533 is comparable to that of DDR266 or PC133 SDRAM and is evidently worse compared to the latency of DDR400 and higher. Thus, DDR2 SDRAM has a higher bandwidth but worse latency than DDR SDRAM, and this is why DDR2-based systems would lose to their DDR-based counterparts in real applications (there are many applications that are sensitive not only to the speed at which data are being transferred to them, but also to the time it takes to access those data).

Besides the higher frequency of the I/O buffers and the use of a twice higher multiplex coefficient, DDR2 has some other unique features, of relatively less importance. The following table lists them:

 

DDR SDRAM

DDR2 SDRAM

Frequency

200, 266, 333, 400 MHz

400, 533, (667, 800) MHz

Chips Packaging

TSOP and FBGA

FBGA

Voltage

2.5 V

1.8 V

Capacity

64 Mbit – 1 Gbit

256 Mbit – 4 Gbit

Internal Banks

4

4 and 8

Prefetch (MIN Write Burst)

2

4

CAS Latency (CL)

2, 2.5, 3

3, 4, 5

Additive Latency (AL)

No support

0, 1, 2, 3, 4

Read Latency

CL

CL+AL

Write Latency

1

Read latency - 1

Input Calibration

No support

Off-Chip Driver (OCD) Calibration

Data Strobes

Bidirectional Strobe (single ended)

Bidirectional Strobe (single ended or differential) with RDQS

On-Chip Bus Termination

None

Embedded

Burst Lengths

2, 4, 8

4, 8

In fact, we can only emphasize the Additive Latency mechanism and the on-chip bus termination. Additive Latency increases the efficiency of data transfers somewhat as it solves the problem that sometimes occurs with DDR SDRAM when a command to read an initialized memory bank and a command to initialize the next bank cannot be issued simultaneously. This innovation brings just a minor performance gain in reality, though.

On-die termination means that the resistors on the end of the bus (to suppress the signal, rather than to let it echo back into the bus) are located on the chip rather than on the mainboard as before. This improves the termination proper and decreases the cost of mainboards as it’s not necessary to put resistors around the DIMM slots.

As said explicitly in the specification, DDR2 SDRAM chips have FBGA packaging. This type of packaging allows for better heat takeoff as well as minimal electromagnetic interference between the chips. Besides the different packaging (DDR SDRAM chips were usually TSOP-packaged), DDR2 SDRAM chips have a smaller power voltage and thus a smaller heat dissipation (about 30 percent less). By the way, this permits to create DDR2 chips of higher capacities and frequencies than it was possible with DDR SDRAM.

New Low-Latency DDR2

So, the weakest aspect of the DDR2 technology is high latency which led to DDR2-based systems having a smaller performance compared to DDR-based ones. And this was the problem the memory manufacturers interested in promoting DDR2 SDRAM in the market have been trying to solve. And they have made some success!

Early DDR2-533 SDRAM modules available at the time of the announcement of i925 and i915 chipsets had 4-4-4 timings (CAS Latency - RAS to CAS Delay - RAS Precharge Time). Today, however, many memory manufacturers, especially the developers of advanced modules for PC enthusiasts like Corsair or OCZ, are offering DDR2 SDRAM capable of working at 533MHz with 3-3-3 timings. These modules are not overclocked, but fully comply with JEDEC’s appropriate standards (the official specification describes a DDR2-533 modification with 3-3-3 timings and a voltage increased to 1.9v).

Intel also approved of DDR2-533 SDRAM with 3-3-3 timings in LGA775 systems. The company has officially confirmed its new chipsets support such memory and even specifically emphasized that such memory would be the best choice for enthusiastic users. Intel’s reasoning is easy to grasp: theoretically, the reduction of the CAS latency of DDR2-533 to 3 cycles is a significant improvement of the parameters of DDR2 SDRAM:

Memory

Timings

Latency

Bandwidth in dual-channel mode

DDR400 SDRAM

2.5–3–3

12.5 ns

6.4 GB/sec

DDR400 SDRAM

2–3–2

10 ns

6.4 GB/sec

DDR533 SDRAM

3–4–4

11.2 ns

8.5 GB/sec

DDR533 SDRAM

2.5–3–3

9.4 ns

8.5 GB/sec

DDR2-533 SDRAM

5–5–5

18.8 ns

8.5 GB/sec

DDR2-533 SDRAM

4–4–4

15 ns

8.5 GB/sec

DDR2-533 SDRAM

3–3–3

11.2 ns

8.5 GB/sec

DDR2-600 SDRAM

5–5–5

16.6 ns

9.6 GB/sec

DDR2-600 SDRAM

4–4–4

13.3 ns

9.6 GB/sec

You can see that DDR2-533 SDRAM with 4-4-4 timings has a half worse latency compared to the widespread DDR400 SDRAM; the 30-percent growth of the bandwidth will hardly compensate such a worsening of the access time. The latency of DDR2-533 improves considerably at 3-3-3 timings, however, and is only 12 percent worse than the latency of 2-3-2 DDR400 SDRAM. As the result, considering that DDR2-533 SDRAM has a higher bandwidth, we can expect DDR2-based systems with reduced timings to be as fast as DDR1-based platforms.

We want to add that the 3-3-3 timings formula is not the evolution end of DDR2-533. For example, OCZ has started to output DDR2 memory modules with even more aggressive timings: the new product, PC2 4200 Enhanced Bandwidth Platinum, has a timings formula of 3-2-2! LGA775 platforms equipped with such memory are going to offer tough competition to platforms with ordinary DDR SDRAM.

Besides that, mainboard makers have also moved one step closer towards a faster LGA775 as many i915/i925-based mainboards for overclockers from ASUS, ABIT and other companies allow to clock DDR2 memory at 600MHz instead of 533MHz. This capability is realized through the use of undocumented memory frequency ratios available in i925/i915 chipsets. Although there’s no DDR2-600 standard ratified, this memory mode is going to increase the memory subsystem bandwidth as well as to reduce its latency a little compared to DDR2-533 with 4-4-4 timings.

Since the manufacturers of memory for enthusiasts are offering not only DDR2-533 memory with low timings, but also DDR2-667 modules capable of working at 600MHz and 667MHz, the use of 600MHz memory in LGA775 systems may be of some practical interest.

In this review we are going to estimate the speed of LGA775 systems equipped with a faster memory than we used in our earlier tests (DDR2-533 SDRAM with 4-4-4 timings). The main question we’re going to answer is if the more progressive DDR2 SDRAM can lift the performance level of i915/i925-based systems to that of i875/i865-based computers. We will also examine some particular DDR2 SDRAM modules which helped us to carry our tests through.

ASUS + Corsair: i865PE Supports DDR533 SDRAM

Talking about the success DDR2 SDRAM has been making in terms of speed and latency, we shouldn’t forget about DDR-based products the memory and mainboard makers continue to improve upon. Of course, the evolution in this area is less turbulent as in the DDR2 field, just because JEDEC’s DDR SDRAM-related standards have long become rock-solid. The development of DDR400 SDRAM ended at the achievement of 2-2-2 timings, so systems with i865 and i875 chipsets seem to have reached their height and seem to have no further reserves for improvement.

But that’s not exactly so. Having successfully mastered the production of DDR400 SDRAM modules with 2-2-2 timings, the manufacturers switched to developing modules capable of working at frequencies higher than 400MHz. For example, even DDR600 SDRAM memory is available in the market now, i.e. it can be clocked at 600MHz. Such memory modules can only be of any interest to overclockers since none of the chipsets supports memory frequencies above 400MHz in its regular operational mode.

Fortunately, mainboard makers addressed this problem. Using undocumented capabilities of the i865PE chipset the engineers made this chipset support 533MHz memory in the regular mode, i.e. at 200MHz FSB. The ASUS P4P800-E Deluxe is among such Socket 478 mainboards. By the way, the ASUS P5P800, an LGA775 mainboard based on the i865PE chipset, features the same capability. Thus, systems with the i865PE chipset have become compatible with faster DDR533 SDRAM memory in the regular operational mode of the CPU.

Still, the use of DDR533 SDRAM hasn’t been of much profit until recently as we saw in our article called Fastest Pentium 4 Platform: Performance of i925, i915, i875 and i865 with DDR2-533, DDR2-400, DDR533 and DDR400 SDRAM. By the results of our midsummer tests, an i865PE-based system with DDR533 SDRAM was no faster than an analogous system equipped with DDR400 SDRAM with 2-2-2 timings.

Things have changed since then. Back in summer we had to use DDR533 SDRAM modules with 3-4-4 timings as faster modules were nonexistent. But now the manufacturers of overclocker-friendly memory have mastered the production of DDR memory capable of working at 533MHz with 2.5-3-3 timings. Such memory modules are evidently going to bring the performance of i865PE-based platforms onto a whole new level.

We have a chance to check this out thanks to Corsair, one of the leading manufacturers of overclocker-friendly memory, who offered us their TWINX1024-4400C25 modules.

These sticks are rated for 550MHz frequency, 2.5-4-4 timings and 2.75v voltage, but they are also perfectly stable at 533MHz frequency with more aggressive 2.5-3-3 timings.

Thus, using a P4P800-E Deluxe mainboard from ASUS and TWINX1024-4400C25 memory modules from Corsair we assembled an i865PE platform that was working at 200MHz FSB, but with high-speed DDR533 memory (2.5-3-3 timings).

DDR2 SDRAM vs. DDR SDRAM: Testbed and Methods

So, it’s time to knock together two platforms: i875/i865 with DDR memory and i925/i915 with DDR2 SDRAM. We will see how the performance of the systems varies depending on the memory timings. We used identical processors and graphics cards in both platforms, so they only differed in the memory type. We took an i865PE-based P4P800-Deluxe mainboard from ASUS as an i875/i865 platform (thanks to its HyperPath technology, this mainboard delivers the same performance as i875P-based products); the i925/i915 platform was based on the ABIT AA8 DuraMAX mainboard with the i925X Express chipset.

Thus, we used the following hardware in our tests:

First, we’d like to offer you the results of synthetic memory subsystem benchmarks:

 

DDR2-533
(3-2-2-8)

DDR2-533
(3-3-3-8)

DDR2-533
(4-4-4-12)

DDR2-600
(4-4-4-12)

DDR400
(2-2-2-5)

DDR533
(2.5-3-3-8)

ScienceMark 2.0

Memory Bandwidth, MB/s

4630

4615

4561

4614

4598

4637

Memory Latency, cycles

257

259

275

282

263

262

Memory Latency, ns

75.58

76.17

80.88

82.94

77.39

77.09

SiSoft Sandra 2005

RAM Int Buffered Bandwidth, MB/s

5066

5029

4949

5064

5020

5064

RAM Float Buffered Bandwidth, MB/s

5066

5037

4943

5062

5010

5061

RAM Int Unbuffered Bandwidth, MB/s

4685

4621

4416

4615

4338

4578

RAM Float Unbuffered Bandwidth, MB/s

4686

4619

4413

4614

4343

4580

The first thing you should have noted in the table is the relatively small difference in bandwidth between various memory types. This is natural since the tests just cannot measure the “pure” memory bandwidth and the numbers are the effective bandwidth of the CPU-memory thoroughfare. The bottleneck in this thoroughfare is not the memory proper, but rather the CPU bus that has a theoretical peak bandwidth of 6.4GB/s at 200MHz frequency. The tested memory just can’t reveal its bandwidth potential here.

Anyway, we can still see the dependence of the bandwidth on the memory type and its characteristics. DDR2-533 with 3-2-2 timings has the best result, closely followed by DDR2-600 and DDR533. The memory subsystem bandwidth with DDR2-533 and 3-3-3 timings equals roughly the bandwidth of DDR400 SDRAM. DDR2-533 SDRAM with 4-4-4 timings which we used in our earlier tests has the worst bandwidth according to the synthetic tests.

As for latency, the rare DDR2-533 memory with 3-2-2 timings has the best latency of all. The more widespread DDR2-533 with 3-3-3 timings has about the same latency as ordinary DDR SDRAM. DDR2-600 and DDR2-533 with 4-4-4 timings make up a group of outsiders.

Thus, the synthetic tests suggest that the reduction of the timings of DDR2-533 memory can pull the performance of LGA775 systems up above the performance of older i865/i875-based platforms. The recently released DDR533 SDRAM with 2.5-3-3 timings cannot save the day, although adds to the speed of last-generation systems. As for the artificially implemented DDR2-600 mode, it doesn’t seem to add any performance at all.

Now let’s see how the different memory types behave in real applications:

The era of DDR SDRAM is coming to its end. The latency of DDR2 SDRAM is approaching that of DDR SDRAM, so the results of the systems with the new memory look quite pleasing now. In fact, DDR2-533 with 3-3-3 timings brings the performance i925/i915-based systems one level up. Computers with Intel’s new chipsets have a higher performance than i875/i865-based systems – you only have to use memory with aggressive timings!

The new DDR533 SDRAM with aggressive 2.5-3-3 latencies cannot become a savior for the i865/i875 chipsets, although it does add some more speed to them.

As we mentioned above, the performance of DDR2-based systems is more sensitive to a lower latency than to a higher frequency. So, we get practically nothing from using DDR2-600 SDRAM with the i925/i915 chipsets.

Thus, DDR2-533 SDRAM with timings below 3-3-3 is the memory that ensures the maximum performance in computer systems for Intel’s CPUs. And the lower these timings, the higher the performance is.

DDR2 SDRAM for Enthusiasts

Having found that good and new DDR2 memory can yield a nice performance bonus for LGA775 platforms, we decided to examine the products currently offered by the leading manufacturers of advanced PC memory. Four manufacturers responded to our request by offering us their DDR2 SDRAM modules: Corsair, OCZ, PQI and GeIL. Below you will find a brief description of each product.

Corsair CM2X512-5300C4PRO (5300C4PRO)

Corsair is the most popular manufacturer of advanced memory modules as the last-year poll conducted on our website said. They offered us their top-end model – a couple of 512MB Corsair CM2X512-5300C4PRO modules (this is what is written on the modules themselves; the same modules are referred to as CM2X512-5400C4PRO on Corsair’s website, so keep this discrepancy in mind when shopping).

The pair of DDR2 SDRAM modules from Corsair is rated to work at 675MHz, 4-4-4-12 timings and 1.9v voltage (by the way these are the conditions under which Corsair’s DDR2 modules undergo tests on the ABIT AA8 DuraMAX mainboard; Corsair’s DDR2 memory also comes with a lifetime warranty).

The modules are equipped with massive aluminum heatsinks whose height is rather bigger than average. This may poise a problem on some mainboards if you use a splaying-out CPU cooler, like Zalman’s CNPS7700. Heatsinks are glued to the modules with a special heat-conductive substance applied on the memory chips.

The exclusive feature of the CM2X512-5300C4PRO modules, which is denoted by “PRO” in the model name, are the nine LEDs of green, yellow and red colors that indicate the load on the module. That’s why these modules are especially beloved by the modding community; this additional illumination on the DIMM modules looks very effective.

The modules’ SPD only tells of one operational mode: 667MHz with 4-5-5-15 timings. Still, this doesn’t prevent you from using them in more aggressive modes, and they did perform well in our practical tests.

GeIL PC2-5300

GeIL also responded to our request and offered us a pair of their 512MB PC2-5300 modules. According to the manufacturer’s website, these modules are intended for 667MHz frequency with 4-4-4-12 timings and 1.9v voltage. These sticks are also claimed to be based on a special PCB that features a low level of electromagnetic interference.

The modules are covered with an aluminum heat-spreader that carries the company’s logo and a sticker with their model number. The heatsinks are glued up with a special sticky heat-conductive pad. GeIL equips some of its modules with a sticker that indicates the temperature of the heat-spreader, but our PC2-5300 sample came without such a sticker.

The modules’ SPD is more informative than the one of Corsair’s modules, but GeIL still does not tell the production date. According to SPD, these modules are operational at 533MHz with 4-4-4-12 timings and at 667MHz with 5-4-4-15 timings. These are somewhat worse parameters compared to those GeIL includes into the specification. Our practical tests revealed that the SPD chip was correct and the manufacturer’s website was wrong. That is, GeIL’s PC2-5300 memory cannot work at 667MHz with 4-4-4-12 timings.

OCZ PC2 4300

OCZ have been very aggressive in the market lately, so we have two pairs of modules from this manufacturer in our labs. The first pair is called OCZ PC2 4300. These modules aren’t anything exceptional, as they are intended to work at 266MHz frequency with 4-4-4-12 timings at the standard voltage of 1.8v. Still, these pair is made according to the traditions of OCZ Technology (manual testing to comply with the specification plus a lifetime warranty).

OCZ PC2 4300 are equipped with two mirror-polished copper heat-spreaders fastened with two steel clips.

These modules do not differ in their parameters from the majority of DDR2-533 memory available, and their “eliteness” doesn’t show up in their SPD: they can work at 533MHz with 4-4-4-11 timings as well as with “weaker” 5-4-4-11 timings.

Well, the noble pedigree of these sticks should have told somewhere and they proved to be exceptionally universal during our tests, supporting a huge number of various operational modes.

OCZ PC2 4200 Enhanced Bandwidth Platinum

The second pair of DDR2 modules we received from OCZ is a real masterpiece of engineering art. The main distinguishing trait of the OCZ PC2 4200 Enhanced Bandwidth Platinum memory is its extremely low timings. For example, these modules are rated to work with 3-2-2-8 latencies at 533MHz, which should result in an extraordinary performance.

These sticks carry copper heatsinks with mirror platinum-color sputter coating and support of Extended Voltage Protection technology that allows for a safe exploitation of the modules at operational voltages up to 2.2v. Of course, these sticks come with a lifetime warranty and are manually tested before packaging and shipping for their compliance with the specification.

The SPD info echoes the official specification: these modules are operational at 266MHz with 3-2-2-8 timings. Our practical tests showed that besides the low timings these modules could boast an excellent operability at high frequencies.

There’s however one compatibility problem: our ABIT AA8 DuraMAX mainboard refused to start up with OCZ PC2 4200 Enhanced Bandwidth Platinum installed.

PQI25400

PQI hasn’t yet become a widely recognized memory maker like Corsair or OCZ, but this company is trying hard to become one of the leading makers of advanced memory modules. PQI offered us a pair of PQI25400 modules intended for 667MHz frequency, 4-4-4-12 timings and 2v voltage.

Like the renowned manufacturers of overclocker-friendly memory, PQI puts all its modules under strict factory tests and supplies them with a lifetime warranty.

The heatsinks on PQI’s memory look solid enough, too. They are two copper plates with mirror-like sputter coating, fastened with a steel clip that carries the manufacturer’s logo.

Although the PQI25400 modules are rated to work at 667MHz, the SPD chip has nothing to say about that. 533MHz is set as the maximum clock rate for that memory, with 4-4-4-11 or 5-4-4-11 timings. Our tests, however, prove that the PQI25400 modules can work at 667MHz, so the official specification is right now, rather than the SPD information.

DDR2 SDRAM for Enthusiasts: Performance Tests

The goal of this test session was to determine the performance of the memory modules from different manufacturers. We selected the default memory timings (by SPD) and measured the performance of LGA775 systems at 533MHz and 557MHz memory frequencies. These frequencies were arrived at by using the standard 3:4 memory divisor at 200MHz and 250MHz FSB clock rate. That is, we checked out DDR2-533 in the regular mode of the CPU, while DDR2-667 memory was tested when the FSB was overclocked to 250MHz.

To test the memory modules in the regular mode at 533MHz memory frequency, we used the “reference” i925XE Express-based mainboard called Intel Desktop Board D925XECV2. To test the memory in the overclocking DDR2-667 mode at 250MHz FSB, we took an ASUS P5AD2-E Premium mainboard which was too based on the i925XE mainboard and offered wide CPU overclocking opportunities.

So, we assembled our test platforms from the following hardware:

DDR2-533 Test Mode

First, here are the results of synthetic tests:

 

Corsair CM2X512-5300C4PRO

GEIL PC2-5300

OCZ PC2 4200 EB Platinum

OCZ PC2 4300

PQI25400

ScienceMark 2.0

Memory Bandwidth, MB/s

4560

4562

4606

4486

4587

Memory Latency, cycles

274

273

270

276

273

Memory Latency, ns

80.58

80.29

79.41

81.17

80.29

SiSoft Sandra 2005

RAM Int Buffered Bandwidth, MB/s

4964

4962

5043

4892

4973

RAM Float Buffered Bandwidth, MB/s

4967

4959

5047

4893

4969

RAM Int Unbuffered Bandwidth, MB/s

4429

4429

4609

4149

4443

RAM Float Unbuffered Bandwidth, MB/s

4432

4432

4609

4149

4446

As might have been expected, the OCZ PC2 4200 Enhanced Bandwidth Platinum memory with the most aggressive timings has the highest performance according to our synthetic tests.

Let’s now see how the choice of the memory modules can affect the performance of the system in general.

The diagrams show that the speed of real applications varies depending on the particular memory module. OCZ’s PC2 4200 Enhanced Bandwidth Platinum sticks boast the highest performance again, while the OCZ PC2 4300 loses in almost all the tests. The modules from PQI, GeIL and Corsair have similar speeds, although different timings are written into the SPD units of these modules.

DDR2-667 Test Mode

Now we will see how the DDR2 SDRAM modules behave at 667MHz frequency. OCZ PC2 4200 Enhanced Bandwidth Platinum memory couldn’t work at this frequency with its default timings, so we had to manually select 5-5-5-12 timings for it.

Synthetic tests come first:

 

Corsair CM2X512-5300C4PRO

GEIL PC2-5300

OCZ PC2 4200 EB Platinum

OCZ PC2 4300

PQI25400

ScienceMark 2.0

Memory Bandwidth, MB/s

5470

5432

5415

5349

5413

Memory Latency, cycles

283

293

294

294

293

Memory Latency, ns

80.75

83.6

83.89

83.89

83.6

SiSoft Sandra 2005

RAM Int Buffered Bandwidth, MB/s

6009

5992

6036

5859

5994

RAM Float Buffered Bandwidth, MB/s

5992

6006

6020

5854

5998

RAM Int Unbuffered Bandwidth, MB/s

5196

5103

5109

4650

5102

RAM Float Unbuffered Bandwidth, MB/s

5195

5108

5105

4651

5104

The Corsair CM2X512-5300C4PRO memory seems to be overall the best in this test, although the OCZ PC2 4200 Enhanced Bandwidth Platinum has the best result in the memory bandwidth test of SiSoft Sandra 2005 with enabled memory prefetch and buffering.

And here are the results in real applications:

Corsair’s CM2X512-5300C4PRO modules provide the highest performance at 667MHz frequency. The sticks from GeIL and PQI have good results against the competitors, too.

DDR2 SDRAM Modules for Enthusiasts: Overclocking

Besides testing the performance of various memory modules, we decided to check them at overclocking, too. We searched for the maximum frequencies DDR2 SDRAM modules were stable at, varying their timings. The tests were performed with an i925XE Express based P5AD2-E Premium mainboard. We set the memory frequency ratio to 4:3 relative to the FSB clock rate and were increasing the FSB clock rate until the system lost its stability.

The whole testbed looked as follows:

First of all we wanted to find the maximum frequency the modules could achieve with 4-4-4-12 timings and 1.9v voltage.

As you see, nearly all of the modules can work at frequencies above 667MHz. The exception if GeIL’s PC2-5300, but you can make them work at this frequency by setting CAS Latency to 5.

As for the leaders, the Corsair CM2X512-5300C4PRO modules, which have already confirmed their highest performance in overclocking modes, reach the highest frequency here. They are accompanied with the OCZ PC2 4200 Enhanced Bandwidth Platinum sticks which are not actually intended for high frequencies. In other words, the OCZ PC2 4200 Enhanced Bandwidth Platinum memory proves to be a versatile product, capable of working at high frequencies or at 533MHz with low timings.

Now let’s try the modules with 3-3-3 timings and 1.9v voltage.

The OCZ PC2 4200 Enhanced Bandwidth Platinum modules conquered the highest frequency at the aggressive timings, which is quite expectable. The remaining modules can only be clocked slightly above 533MHz with these timings, and the PQI25400 sticks couldn’t work with 3-3-3 timings at all.

Conclusion

DDR2 SDRAM has become faster! Earlier we had to admit that memory of that type had a lower performance than ordinary DDR400 SDRAM in real applications due to a too high latency, but now it’s time to revise this supposition. New DDR2-533 SDRAM modules with timings reduced to 3-3-3 can challenge fastest DDR400 SDRAM sticks, and this means that one of the main disadvantages of the LGA775 platform is eliminated. Now the transition to an i925/i915-based mainboard becomes the more appealing option. The only thing to take care about is the choice of the particular DDR2 memory modules as their quality will determine the speed of your computer.

Considering the fact that DDR2 technology is going to develop towards both lower timings and higher frequencies, its advantages over DDR SDRAM become the more conspicuous. DDR2 modules with more aggressive timings are most likely to appear in the future, boosting the performance of the LGA775 platform even higher.

As for recommendations about the choice of memory, all DDR2 SDRAM kits presented in this review deserve your attention, but we would want to specifically mention the PC2 4200 Enhanced Bandwidth Platinum modules from OCZ that feature an excellent speed and overclockability. If it were not for the compatibility problems we met when testing this memory, we’d call it the best offer for today. The Corsair CM2X512-5300C4PRO modules offer an impeccable compatibility with different mainboards; they are fast and support aggressive timings at 533MHz frequency.