DDR vs. DDR-2 - What are we to make of it all?

Today we have posted an article for you which investigates the current state of DDR vs. DDR-2 memory in the industry. We have included in-depth information about what is different about the two technologies, possible adoption problems for AMD with Athlon 64 and benchmarks comparing both on an MSI motherboard which supports both memory standards. If you're wondering what we are to make of it all... Read on!
Published Sun, Oct 3 2004 11:00 PM CDT   |   Updated Tue, Apr 7 2020 12:26 PM CDT
Manufacturer: none

DDR vs. DDR-2 - Introduction

IntroductionDDR SDRAM has been the biggest savior for the Intel Pentium 4 platform. It has taken it from a status of "avoid like the plague" to one of total acceptance. During the Pentium 4's early life, Intel had a major hard time convincing its OEM and retail customers to purchase a Pentium 4 system simply because of expensive processors and not to mention an expensive and rather lacklustre RAM imitative called RDRAM.Licence agreements with Rambus put Intel on the back foot with DDR, as they had agreed to support the RDRAM series memory on their I850 Pentium 4 chipsets. This caused much uproar, as the price/performance or RDRAM was totally off the scales - nobody wanted to touch it with a 10 meter cattle prod. When these licensing agreements were over, Intel flooded the market with the I845x series chipsets. These all supported single channel DDR memory.Dual Channel DDR was the only way to satisfy the bandwidth hungry Pentium 4 processor, as its bandwidth of upwards of 4.2GB/s just couldn't be satisfied with a 2.7GB/s of DDR-333 memory.Now DDR has reached its maximum frequencies of around the 466MHz mark, and even then extra voltage is required in order to reach these speeds, and with the instability of some modules, it has become apparent that DDR is now at the end of the speed highway. It's now time for something else to take over that is somewhat faster, but not all that different that is causes the same performance problems RDRAM once did. Enter DDR-2.Today we pit DDR-400, the fastest JEDEC standard memory against the DDR-2 533MHz, the currently fastest DDR-2 JEDEC standard to see just what a system based on this memory can actually do.

DDR vs. DDR-2 - DDR2 in Detail

DDR-2 in DetailPrepare yourself as we will be going into the heart of DDR-2 technology here.DDR-2 technology is a direct extension of the already popular and mature DDR technology. In fact, the reason DDR-2 and DDR is almost identically compatible and require minimal reconfigurations of the DRAM controllers is that is has the identical same command structure, just a slightly different way of going about its processing of the data. What does this all mean? Well let's have a look at the DDR-2 architecture and how it actually works compared to the DDR technology.DDR SDRAM uses a simple premise - it takes the existing command issue structure and DQ (or Data Queue) and allows the array to send two bits of data per clock cycle rather than the standard one of SDR. This is done by using both the rising and falling edges of the clock cycles, effectively allowing you to send twice the data at the same bus frequency. This is how DDR was able to get 200MHz rating while still using a 100MHz bus speed.DDR-2 uses the exact same sending technique, two bits per clock cycle, however, the internal memory cell array and buffers have been changed.
Here we see how DDR-2 allows a much broader range of data to be sent which is achieved by effectively a dual core system. Two cores are added to the cell array allowing both to operate independently; each core has the two bit system, which doubles this to four bits total. The data buffer in order to allow both the cores to operate at their peak runs at twice the speed of the cell array, allowing each array to dump its memory into the buffer for the trip along this bus. While the bus remains at the same speed, this new architecture works something like the Intel Quad Data Rate bus in order to give 4 times the speed of the internal clock. DDR at 100MHz clock has a speed of 200MHz and DDR2 at 100MHz clock is effectively 400MHz. This is how DDR-2 gets it speed increase, as it allows the clocks to be lowered while increasing the overall data throughput. With this in mind, 200MHz DDR put into a DDR-2 fashion would give us 800MHz, well beyond that of the DDR capabilities.Added to this is the major issue of the maximum speed obtainable today. Sure 800MHz is good but more is needed when we are looking at pushing beyond what is available today. This is where DDR-2 distinguishes itself from DDR with a few additional tricks up its sleeve. First off is the reduction in manufacturing processes, allowing for a smaller die which is able to push beyond what DDR is capable of. DDR-2 is a standard in the FBGA or Fine Ball Grid Array Package. This package is not totally dissimilar to that used by Kingmax Technology with its TinyBGA system for many of the past years and in fact, it is almost identical. This means that the units will generate less heat, and require less power. When you put a Smaller Die + Cooler running package + lower voltages you will end up with clock speeds beyond what is available in DDR modules, and should soon see 1GHz DDR-2 modules starting their testing phase with some enthusiast memory companies such as OCZ and Corsair already selling 675MHz DDR-2 modules.DDR-2 uses a new voltage requirement that DDR just can't match. With the lower heat generation and smaller packages, the required voltage for DDR-2 has been set at an amazingly low 1.8 volts. This was achieved by replacing the single way differential strobe with a bidirectional I/O buffer strobe.One of the most significant changes to the system is the new On Die Termination. On DDR motherboards the signal termination was handled by resistors on and around the motherboard DRAM sockets. When at the lower 266MHz and 333MHz speeds this works out quite well, however, when pushing up clock frequencies, the requirement for terminating the bus noise become a crucial one, and DDR just gets too noisy with the termination system on the motherboard itself. DDR-2 changes this by incorporating an on die resistor that connects to the main ground of the DRAM channel. This allows signal noise and reflections to be cancelled out on the actual die of the memory package. This helps as the noise from one module won't travel along to another module and cause further havoc as well as keeping the noise on the actual package to a total minimum, allowing a much cleaner signal to flow along the bus.

DDR vs. DDR-2 - DDR2 in Detail Continued

DDR-2 in Detail ContinuedDDR-2 while having a similar command set, it requires a totally different memory socket. This is why DDR and DDR-2 modules can't be interchanged in the same sockets. DDR runs on a 184 pin socket, where DDR-2 uses a 240 pin socket. The extra pins are used for the second core on the chip as well as extra signal voltage pins. DDR-2 however, does give some advantages as it can be in a term retarded back to allow DDR memory modules to exist on the same motherboard as DDR-2. Some motherboards have appeared with both DDR and DDR-2 memory module sockets which just goes to show the similarities between the two technologies. Intel's own I915 series chipsets support both DDR and DDR-2 memory technologies. You can have Dual Channel DDR or Dual Channel DDR-2 and while you may find both sockets on the one motherboard, you can't use them both at once, as they share the same data address paths, and would simply conflict. However, it does allow users to go to I915 chipsets and keep their DDR until DDR-2 matures into a more mainstream product.DDR-2 does have its advantages over DDR, but it falls behind in one aspect - latencies or the time it takes to perform certain tasks. DDR runs at usually CL3, CL2.5 and some high performance modules run at CL2, though CL2.5 is more common for higher speed memories over 400MHz. DDR-2, due to its nature of dual cores increases latencies to CL5 and CL4 and for the higher performance modules CL3 although CL3 isn't available yet which makes CL4 the lowest available at the moment.This won't affect the Intel Pentium 4 series as much as it would the AMD series CPU's which seem to crave lower latencies rather than raw bandwidth which is one advantage for Intel as DDR-2 533 can offer 8.5GB/s and with 667 modules now starting at 10.5GB/. With DDR-2 speeds set to push bandwidth to the ultimate, you will soon see a lot of programs written for high bandwidth utilisation.DDR-2 possesses a slight complication in adoption for AMD64 users, as it simply cannot be done on the current 754 and 939/940 packaging. As most already know, AMD places its DDR memory controller and primary Northbridge onto the CPU die. While this does eliminate the need for a memory bus controller and CPU to system controller as AMD wanted, when new memory standards hit, it's slow to change over.With DDR-2 requiring a new socket and new pinouts, AMD will have to re-design its K8 CPU with a DDR-2 memory controller as well as a new socket, as extra pins will be required for the DDR-2 memory controller. When AMD swapped over from Single Channel memory in its 754 pin to Dual Channel Memory controller in the 939, the pin requirements jumped by 185 pins, the exact amount needed to add a second channel.So if AMD wanted to have a Single Channel DDR-2 and Dual Channel DDR-2 solution in the K8, we would have to see a socket 808 to replace the 754 and a Socket 1048 to replace 939 which is simply too much cost to the consumer, especially with the already super exorbitant prices of AMD K8 on the 939 package.

DDR vs. DDR-2 - The Modules

The ModulesDDR-2, while not as fast on the uptake as DDR was, is starting to make its mark on the industry. While having one big partner behind you, it doesn't always guarantee an instant audience. DDR only had VIA on its side when it started and it wasn't really till Intel and SiS took the DDR bandwagon that sales of DDR memory really hit the roof - the same can be projected for DDR-2. Intel may be behind DDR-2 all the way, but with AMD sticking to DDR for the time being, it might face a slightly less than stellar sales margin. With that said, there are already a few modules on the market, and we were lucky enough to get our hands on some Mushkin DDR-2 modules rated for 533MHz.
Mushkin packs its DDR-2 in a Dual Channel pack, like it has done for its DDR memory. DDR-2 is set for mostly 128-bit interface, and since the modules haven't been designed for 128-bit natively, two modules are required to get the best out of the system. This kit we received was a 1GB pack using 2 x 512MB DDR-2 DIMM modules.
Outside the package we get a look at the modules themselves. With the new package technology DDR-2 uses, it isn't necessary for DDR-2 modules to need any kind of external cooling for modules rated to 1GHz and beyond, however, Mushkin knows where this memory is going - overclocked systems - where extra voltage gives extra heat, so the added heatspreader is quite welcomed.
With the heatspreader removed we get a look at the RAM modules themselves. Compared to existing BGA memory like video card and Kingmax's TinyBGA, it is somewhat smaller due to a reduction in die size, despite having a dual core system, it comes out smaller in size. The chips themselves are suppled by Micron who does a lot of the wafers for many memory companies out there (you would be surprised how much Micron is involved in a lot of memory companies).Mushkin has set this modules timing system to the JEDEC recommendations for DDR-2 at 533MHz, these are 4-4-4-12, somewhat higher than that of the DDR modules we have seen, though DDR-2 trades off latencies for extra speed and bandwidth, which is where DDR-2 will take over from DDR when 1GHz modules hit the market.

DDR vs. DDR-2 - Benchmarks - Test System Setup and SiSoft Sandra

Test System SetupProcessor: Intel Pentium 560 3.6GHz (800MHz FSB) (Supplied by Spectrum Communications)Motherboard: MSI 915P Combo (Supplied by MSI)Hard Disk: 2x Maxtor Maxline III 250GB SATA (RAID 0)Graphics Card: Gigabyte GeForce PCX5900 (Supplied by Gigabyte)Operating System: Microsoft Windows XP Professional SP2Drivers: nVidia Forceware 61.77 and DX9cWe used the MSI 915P Combo for two major reasons:1) It has both DDR and DDR-2 memory sockets, allowing us to keep the platform unchanged in regards to graphics cards, CPU and the like2) Its overclocking was much higher than any other dual memory motherboard availableOn the settings side, we set the BIOS to run the memory at default timings by the SPD and at their maximum rated, so DDR was at 400MHz and DDR-2 was at 533MHz.SiSoft SandraVersion and / or Patch Used: 2004 SP2Developer Homepage: Homepage: It Here
SiSoft Sandra (System ANalyser, Diagnostic and Reporting Assistant) is a synthetic Windows benchmark that features different tests used to evaluate different PC subsystems.
While these are synthetic benchmarks, we can see that DDR has now reached its limits. At default speeds DDR-2 is much faster than DDR, however, when overclocking the latencies of DDR-2 start to take its toll - though in front, it is only just.

DDR vs. DDR-2 - Benchmarks - PCMark

PCMarkVersion and / or Patch Used: 2004Developer Homepage: http://www.futuremark.comProduct Homepage: It Here
PCMark is a multipurpose benchmark, suited for benchmarking all kinds of PCs, from laptops to workstations, as well as across multiple Windows operating systems. This easy-to-use benchmark makes professional strength benchmarking software available even to novice users. PCMark consists of a series of tests that represent common tasks in home and office programs. PCMark also covers many additional areas outside the scope of other benchmarks.
Here we can see that DDR-2 is still able to keep ahead of DDR but only just.

DDR vs. DDR-2 - Benchmarks - 3DMark03

3DMark03Version and / or Patch Used: 340Developer Homepage: http://www.futuremark.comProduct Homepage: It Here
3DMark03 is the latest version of the highly favored 3DMark series. By combining full DirectX9.0 support with completely new tests and graphics, 3DMark03 continues the legacy of being industry standard benchmark.Please Note: Due to recent events with the 3DMark03 series, we are adding results purely for those who are still in favor of 3DMark03. These results should not be taken too seriously and are only added for interest sakes.
Here we see DDR and DDR-2 almost neck and neck at default speeds and DDR just able to edge out DDR-2 in overclocked.

DDR vs. DDR-2 - Benchmarks - Halo PC

Halo PCVersion and / or Patch Used: RetailDeveloper Homepage: http://www.bungie.netProduct Homepage: It Here
Though we have used Halo in a couple of benchmarks in the past, it has now found a permanent place in our Benchmark Suite. This is simply due to its support for the latest DirectX 9 API's to put some more stress on the system to determine the best of the best.
Here we see that DDR is able to take out DDR-2 due to its lower latencies.

DDR vs. DDR-2 - Benchmarks - Unreal Tournament 2004

Unreal Tournament 2004Version and / or Patch Used: 3323Developer Homepage: http://www.atari.comProduct Homepage: It Here
Unreal Tournament 2004 or UT2004 for short is the latest instalment to the Unreal Tournament series. The full version of the game is based on DX9 (the demo only uses DX8.1 like UT2003) and has faced quite a big make over and is a lot more intensive then its predecessor.
Again DDR-2 falls short of DDR.

DDR vs. DDR-2 - Final Thoughts

Final ThoughtsDDR-2, like most new technology that is here to stay, is something that has to be proven over time. DDR so far has the upper hand, as its lower latencies and bandwidth matching performance shows that higher bandwidth in theory isn't always better, but to be frank it is hard to draw definite conclusions from this due to a number of factors.First we are dealing with first generation DDR-2 modules as well as first generation DDR-2 motherboard chipsets. DDR didn't fully blossom until the third and forth generation chipsets started to take advantage of this new technology, and they have had since 1999 to the present day to perfect this technology, and perfect it they have. Second we are dealing with only one platform that has a nature of starting out slow and building up, after all, Pentium 4 when it first came out wasn't any faster than the Pentium 3, but we can't say that today, with the performance of the P4 now being at the 4GHz doorstep we see that the architecture is developed into a usable source, which is what DDR-2 must do.We can only hope that the upcoming 1066FSB Pentium 4 and 925XE chipsets have better optimisations for DDR-2, as the extra bandwidth of DDR-2 at 533MHz is simply wasted, where it should be used for graphics card use or other high bandwidth systems, after all the P4 has its 6.5GB/s, the rest on the current 9xx chipset just wastes the remaining 2GB/s.

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