<!—#set var="article_header" value="Unstoppable:
DDR400 vs. Rambus» —>
Full Speed Ahead: DDR400 vs. RDRAM (PC1200)
The role that the processor plays in determining the performance of a PC system is often overestimated by many users. In practice, slow RAM modules in combination with the chipset are what hampers optimal performance — the result is that the CPU cannot run on a full load.
A hand-picked DDR400 memory module from Infineon (engineering sample), which was able to run at over 200 MHz memory clock without any difficulties. Even at a setting of CL2.5, the test platform ran stably. Infineon «officially» states that they not produce DDR400 for the time being.
The cards are on the table. In the race to achieve the highest memory performance, we used the most powerful, hand-picked modules straight from the labs of the manufacturers. Let’s start out with some concrete numbers first: with the DDR400 module the latency is 2.5, and the RDRAM modules include special versions for 600 MHz memory clock (PC1200). Here, the access time is 32 nanoseconds, and in the meantime, the fastest modules with 35 ns are due to hit the market in a few weeks. So the occasion that gave rise to this test is obvious: with the onslaught of motherboards and memory modules for DDR3 on the market, the question to ask is to what extent the overall performance can be boosted with DDR200 and DDR266. In addition, the Rambus platform with the Intel Pentium 4 has become available for prices that are more reasonable than ever before. The fact is unavoidable: RDRAM memory for PC800 (400 MHz memory clock) is sometimes even less expensive than DDR333 memory (166 MHz memory clock and CL2.5).
Full Speed Ahead: DDR400 vs. RDRAM (PC1200), Continued
Currently, only the SiS 645DX chipset (for the Pentium 4) supports an asynchronous memory clock of 200 MHz — in the meantime, the FSB clock runs at 100/133 MHz. There’s still no DDR400 platform for the AMD Athlon. This picture shows you details from the BIOS of the reference board from SiS.
DDR memory alone is no longer the end-all, be-all, and this is illustrated by the development in RDRAM modules. Soon, modules with 533 MHz will be available — our test samples from Samsung make a positive impression. The introduction of PC1200 shows that the company Rambus is not ready to die yet. The real question is, which memory technology will come out stronger in the near future? Rambus doesn’t exactly hold the cards in its hands, since Intel, its main sponsor, let itself be influenced by the market, with the result that it is now marketing DDR as the ultimate technology. However, the Pentium 4 platform has an optional Rambus interface and the corresponding chipset support. AMD CPUs work with DDR memory or outmoded SDRAM modules only.
DDR400 memory in action with the SiS 645DX. The exact clock speed of the Pentium 4/2400 is not shown.
In this article, we’ll show you how fast DDR400 memory really is in comparison to RDRAM with 400 MHz, 533 MHz and 600 MHz. Furthermore, we’ll bring you extensive benchmarks that reveal the differences between DDR400, DDR333, DDR266 and DDR200.
Confidential: Rambus Develops Memory Interface For SiS
Even though Rambus only markets the technology rights and does not produce its own memory modules, the company stocks still haven’t sunk to the level of pennies. Ever since Intel turned away from Rambus memory, Rambus has been left searching for new possibilities to market its memory technology. A new partner for Rambus is the Taiwanese chip maker SiS, which has already made waves with its 645DX. A glance at the internal documents shows that Rambus is working on a fast memory interface for the new SiS 648 chipset for Socket 478 (Pentium 4). The well-known motherboard manufacturers are already counting on the SiS 648 chipset. A further development phase has to do with the Rambus memory itself: in a few weeks, new memory modules with a 32-bit data bus will appear on the market. These will offer an additional solution to the conventional modules with 16-bit. So not only do you get the expected boost in speed, but you only need to install one module.
The Future Of DDR: DDR400 And DDR533
Variable clock speeds with the SiS 645DX reference board.
Among the experts, DDR SDRAM technology is considered to be the one that is the most promising and has the most possibility for further development — this is proven by the numerous discussions at the most recent conventions and events. Still, there are problems regarding limited bandwidth, and above all the latency, all of which are sufficiently known, and which some users simply do not consider. DDR SDRAM is a logical continuation developed from DRAM technology, but it is by no means the final word. Also, the connection from the memory module to the chipset is critical. Only an optimized memory interface of the chipset allows for maximum performance with DDR modules. Although the first DDR400 samples are already available, in the short term there’s no chipset on the market that can squeeze optimum performance out of DDR400. VIA is working on KT400, but the latency time that the validated modules will have is still unclear.
Test Setup and Details
| Intel Hardware Socket 478 |
|
| Processor | Intel Pentium 4/2400 MHz (100/133 MHz FSB) |
| Memory | |
| Memory 1 (RDRAM) | 2 x 128 MB, RDRAM, 400 MHz, Samsung, 40 ns |
| Memory 2 (RDRAM) | 2 x 128 MB, RDRAM, 533 MHz, Samsung, 35 ns |
| Memory 3 (DDR266) | 256 MB, DDR-SDRAM, 133 MHz, CL2.5 |
| Memory 4 (DDR266) | 256 MB, DDR-SDRAM, 133 MHz, CL2 |
| Memory 5 (DDR333) | 256 MB, DDR-SDRAM, 166 MHz, CL2.5 |
| Memory 6 (DDR333) | 256 MB, DDR-SDRAM, 166 MHz, CL2 |
| Memory 7 (DDR200) | 2 x 128 MB, DDR-SDRAM, 100 MHz, CL2 |
| Memory 8 (DDR400) | 256 MB, DDR-SDRAM, 200 MHz, CL2.5 |
| Memory 9 (RDRAM) | 2 x 128 MB, RDRAM, 600 MHz, Samsung, 32 ns |
| General Hardware | |
| Graphics Card | GeForce 3 Ti 500 Memory: 64 MB DDR-SDRAM Memory clock: 250 MHz DDR Chip clock: 240 MHz |
| Hard Disk | 40 GB, 5T040H4, Maxtor UDMA100 7200 rpm 2 MB Cache |
| Drivers & Software | |
| Chipset Driver (Intel) | 4.08. |
| AGP Driver (SIS) | V1.09 |
| Graphics Driver | Detonator 4 Serie 28.32 |
| DirectX Version | 8.1 |
| Operating System | Windows 2000, Service Pack 2 |
| Benchmarks & Settings | |
| Quake III Arena | Retail Version 1.16 command line = +set cd_nocd 1 +set s_initsound 0 Graphics detail set to ‘Normal’ Benchmark using ‘Q3DEMO1’ |
| SiSoft Sandra 2002 | Professional Version |
| MPEG-4-Encoding | Xmpeg/Flask 4.5 DivX 5.01 Compression: 100 Data Rate: 1500 Kbit Format: 720×480 Pixel@25 fps no Audio |
| PC Mark 2002 | |
Pentium 4/2400 running at 133 MHz FSB.
Pentium 4/2400 running at 100 MHz FSB.
Speed Comparison: DDR400 vs. DDR333 vs. DDR266
This graph shows the performance of various memory modules, each of which was used in an identical system configuration. All of the measurements are based on the SiS 645DX chipset.
The MPEG-4 encoding test shows just how the performance depends on the memory that is used: together with DDR200, the test platform achieves 22.8 frames per second, but when DDR400 is used, the performance increases by almost 50% to reach 31.8 fps. The PC Mark 2002 benchmark delivers additional figures to reflect the increased bandwidth of DDR modules with a faster memory clock.
Speed Comparison: DDR400 vs. DDR333 vs. DDR266, Continued
The SiSoft Sandra 2002 Pro Memory Benchmark shows the exact bandwidth of the various memory modules. However, we cannot vouch for these figures in practice.
Equal Bandwidths: DDR400 And RDRAM (PC800)
| Label | Name | Effective Clock Rate | Data Bus | Bandwidth |
| PC66 | SDRAM | 66 MHz | 64 Bit | 0,5 GB/s |
| PC100 | SDRAM | 100 MHz | 64 Bit | 0,8 GB/s |
| PC133 | SDRAM | 133 MHz | 64 Bit | 1,06 GB/s |
| PC1600 | DDR200 | 100 MHz | 64 Bit | 1,6 GB/s |
| PC1600 | DDR200 Dual | 100 MHz | 2 x 64 Bit | 3,2 GB/s |
| PC2100 | DDR266 | 133 MHz | 64 Bit | 2,1 GB/s |
| PC2100 | DDR266 Dual | 133 MHz | 2 x 64 Bit | 4,2 GB/s |
| PC2700 | DDR333 | 166 MHz | 64 Bit | 2,7 GB/s |
| PC2700 | DDR333 Dual | 166 MHz | 2 x 64 Bit | 5,4 GB/s |
| PC3200 | DDR400 | 200 MHz | 64 Bit | 3,2 GB/s |
| PC3200 | DDR400 Dual | 200 MHz | 2 x 64 Bit | 6,4 GB/s |
| PC4200 | DDR533 | 266 MHz | 64 Bit | 4,2 GB/s |
| PC4200 | DDR533 Dual | 266 MHz | 2 x 64 Bit | 8,4 GB/s |
| PC800 | RDRAM Dual | 400 MHz | 2 x 16 Bit | 3,2 GB/s |
| PC1066 | RDRAM Dual | 533 MHz | 2 x 16 Bit | 4,2 GB/s |
| PC1200 | RDRAM Dual | 600 MHz | 2 x 16 Bit | 4,8 GB/s |
| PC800 | RDRAM Dual | 400 MHz | 2 x 32 Bit | 6,4 GB/s |
| PC1066 | RDRAM Dual | 533 MHz | 2 x 32 Bit | 8,4 GB/s |
| PC1200 | RDRAM Dual | 600 MHz | 2 x 32 Bit | 9,6 GB/s |
The table above lists the theoretically possible bandwidths of the individual memory modules.
DDR-SDRAM vs. RDRAM: Different Chipsets Compared (UPDATED)
Here, we provide you with various benchmarks that give you a good visual representation of memory performance. In addition, we use different chipset platforms in order to show you how the memory performance depends on the memory interface of the chipset. Keep in mind that some of the chipsets used in our tests are not yet available on the market.
Overview Of Memory Modules
DDR400 with CL 2.5 from Winbond.
Not yet available on the market: DDR333 modules with CL2 from Samsung, Infineon and Corsair.
Available in stores: DDR333 modules with CL2.5 from Micron, Kingmax and Infineon. The module from Infineon also runs in CL2 mode with some boards.
Overview Of Memory Modules, Continued
Two DDR266 memory modules from Micron with CL2. The upper module is an ECC version (e.g. for dual AMD Athlons), which is much more expensive than normal memory modules.
Various DDR modules for 100 MHz and 133 MHz clocks. All modules are designed for CL2 operation.
Overview Of Memory Modules, Continued
Rambus: shorter access times mean more speed. While the top RDRAM module works with 45 ns and is designed for 400 MHz, the third module with 35 ns can work with a clock speed of 533 MHz. The last module with 32 ns is able to handle 600 MHz memory clock (PC1200) without a problem. For safety reasons, the manufacturer has certified the memory for PC1066 (533 MHz).
Various RDRAM modules with 128 MB.
Conclusion: DDR400 Outperforms RDRAM (PC800) — Much Depends On The Chipset
Out tests with hand-picked memory modules ranging from DDR400 to RDRAM (PC1200) show that, with an identical system configuration, a performance boost of almost 50% is possible. Note here that this is in combination with the same processor. While DDR200 brings up the rear of the performance ranks, RDRAM with 533 MHz and 600 MHz reach the top performance levels.
A special topic is the further development of DDR memory: currently, only DDR333 modules with CL2.5 for 166 MHz memory clock are available. In most cases, these modules are not faster than DDR266 with CL2. A distinct increase in speed is offered by DDR333, but only in the CL2 version. DDR400 memory is only at its starting phase — the first of these modules will probably be available with a CAS latency of 3, followed by modules with CL2.5. We were pleasantly surprised by a new chipset, which will officially be launched at the end of May. The manufacturer has optimized the memory interface of the new chipsets, so that the future chipset impressed us in the memory tests. In all of the benchmarks, the combination of the new chipset with DDR333 outperformed Intel 850 with RDRAM and 400 MHz memory clock. Nevertheless, RDRAM with 533 MHz (PC1066) still sets the performance standard, even DDR400 is not quite able to reach the same performance level.
The results of the SiSoft Sandra 2002 Memory Benchmark speak for themselves.
At the moment, the price for Rambus memory is quite inexpensive, so it’s worthwhile to consider buying or putting together the corresponding systems. Rambus still has a right to claim a share of the market, which is evidenced by the fact that numerous motherboard manufacturers, such as Asus, Aopen, Biostar, MSI and Iwill, will soon be coming out with boards that support RDRAM. The reason for this is that in many stores, a PC800 module costs less than DDR333 memory with CL2. However, this development should not be overestimated.
