In the end of 2001 and in the beginning of 2002 Kentron Technologies attracted a lot of attention among industry observers by claiming that their QBM (Quad Band Memory) DRAM will be implemented in the up and coming core-logic devices from certain developers during 2002. VIA told us that they will support the new standard in the P4X333, but after all, they failed and even P4X400 does not support QBM. That should be the end of QDM DRAM, however, recently both VIA and Kentron announced that the former will provide QBM DRAM memory support in their future Pentium 4 chipsets. According to the statement, the company prepares to launch the actual product in the first quarter of 2003.

QBM (Quad Band Memory) DRAM is very interesting type of memory so to speak. It allows to double the memory sub-system bandwidth using the widely-spread DDR SDRAM. Modules, that correspond to QBM standard make use of ordinary memory chips mentioned above. However, thanks to using an additional PLL, half of the chips work at 90 degrees displaced frequency, hence, data becomes available almost two times more frequently compared to ordinary modules. Basically, such way of functioning resembles a 128-bit memory module with a pair of 64-bit channels that switch, in turns, one over another. The linear peak bandwidth of such memory system can be up to 4.2GB/s when using ordinary 266MHz memory chips (PC2100). Moreover, since QBM utilises the same 184-pin design of modules, mainboards to support QBM will allow to install ordinary DDR SDRAM as well.

This year VIA Technologies will unleash its P4X600 that supports dual-channel PC2700 DDR SDRAM and in the first quarter of 2003 the company plans to launch the P4X800, that supports QBM SDRAM. Both core-logic devices are intended for the Pentium 4 processors with 400/533MHz system bus, maybe the latter will even offer 667MHz FSB, but it is still to be confirmed. VIA has no plans to introduce QBM chipsets for AMD platform as today’s Athlon XP with 266MHz processor bus are not able to take advantage of such system memory, while the ClawHammer code-named CPUs have integrated memory controller, hence, there is no need to have one in the North Bridge.

In fact, QDM memory implementation can give a serious performance boost in certain cases, especially for platforms that support the data-hungry Pentium 4 processors and have a powerful graphics core integrated into the North Bridge.

Memory makers like Elpida and Infineon already said that they plan to manufacture QBM (Quad Band Memory) DRAM modules, but declined to comment about the timeframes. ST Microelectronics already makes necessary PLL chips which cost about $1, as a result, module makers can start the production even now. Analysts estimate that QBM products will not cost more than 10 to 15% compared to ordinary DDR SDRAM ones.

Although QBM (Quad Band Memory) DRAM has loads of advantages over ordinary DDR SDRAM, it has a very few chances to become massively available on the market. Firstly because VIA does not want to secure its license on the Pentium 4 system bus and mainboard makers do not want to use their Pentium 4 core-logic products, having a fear of Intel’s anger. Secondly, since VIA is always trying to implement new and rather exotic types of memory and constantly fails. It is their third try, as far as I remember. In 1997 they said BEDO RAM was useful and powerful and added the support of such memory to Apollo VPX, VP1 and VP2 chipsets. I cannot remember such memory modules for sale anywhere. In 1999 they decided that VCM (Virtual Channel Memory), allowing to open up to 16 independent cached memory channels, reducing delays and latencies, will be widely spread. Well, they declared the support for this type of memory in all their chipsets, however, I remember only one time such memory modules appeared for sale, in limited quantities in Japan. It was in Summer 2000 and VIA was ahorse at that time, thus, memory makers were pretty interested in manufacturing such modules. Now VIA’s market share decreases, module vendors will be very sceptical about introducing products that will not be much in demand, especially considering the present situation in the industry.

SiS and ALi also participate in QBM Alliance, however, both companies still have not indicated their desire to implement such kind of memory support. Furthermore, SiS is quite serious about its RDRAM and dual-channel DDR SDRAM chipsets. Even if all three Taiwanese core-logic developers announce the actual support of QBM in their chipsets, the memory modules will not become massive anyway, simply because Intel the powerful targets dual-channel DDR SDRAM in 2003 and dual-channel DDR-II SDRAM in 2004.

Of course, keep hope alive, maybe Quad Band Memory is another revolution.