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Whatever happened to...Quad Band Memory?

26 December 2002

By: Agitator!!

I was going over some old press releases for an another article I'm doing, when I came across this one from S3 dated September 17th. It mentions a license agreement between S3 and Kentron for incorporating Quad Band Memory (QBM) technology into core logic chipsets.

    This license marks the first time that PC based systems will be able to interface to high speed DDR533 and DDR667 modules featuring QBM technology. New systems using QBM enabled chipsets from VIA and S3 Graphics will combine the fastest speed memory in the industry with the fastest processor bus speeds and maintain backward compatibility with today's DDR modules.

S3 is not the only company to announce support for QBM. However, most of the intial announcements of QBM support were from earlier in the year. It's is now the end of 2002 and there is still no QBM products on the market.

So what is Quad Band Memory? Well, QBD attempts to address the memory subsytem bottleneck by using standard DDR memory and its associated 184-pin DIMM interface. They do this by taking two banks of DDR and delaying the second bank by 90 degress. By using advanced switching techniques, they are able to generate 4Bits/cycle versus the standard 2Bits/cycle.

The switch component is the key in QBMís bit packing technique which provides twice the bandwidth of standard DDR devices. The QBM switch component also acts as an On / Off switch to turn off the QBM modules not in use in a system, thus reducing the capacitive load on the memory bus and allowing for greater system density. For a more indepth discussion of QBM, take a look at this pdf file.

Kentron claims that QBM offers superior price/performance ratio over upcoming technologies like DDR-II. But if that is the case, why isn't it being utilized already?

According to Kentron, QBM is not dead. In fact, they recently announced support for DDR400.

    Kentron Technologies has announced that its family of high performance QBM memory modules will support the DDRI-400 DRAM devices expected to become mainstream in the 2nd half of 2003.
So while DRAM manufacturers like Samsung, Micron, Hynix and Elpida focus their resources on improving bandwidth at the device level, Kentronís approach improves speed and density on the module or "platform" level using standard, "off-the-shelf" DRAM devices.
    By combining the low cost, QBM switch component and DDRI-400 devices, Kentron and its partners will deliver QBM800 modules that match the 800MHz front side bus of new system processors (CPUs) expected to be available in the 2nd half of 2003. The QBM800 modules will operate up to 6.4 GB/sec (single-channel) and 12.8 GB/sec (dual-channel) and will be positioned as the lowest cost and highest performance memory modules in the industry. Kentron and its channel partners will be introducing QBM533 (4.2 GB/sec) modules using DDRI-266 memory devices in Q1 of 2003.

What products will be able to take advantage of QDM? It appears that the new P4X800 chipsets from VIA Technologies, Inc. may be the first.

The QBM533 modules combined with the VIA P4X800 memory controllers will match the fast 533MHz front side bus of CPUs and provide the highest performance single channel solution in the system marketplace. As the CPUs move to the faster 667MHz and 800MHz front side bus, Kentron will be providing QBM based solutions to meet those speeds using available low cost DDRI-333 and DDRI-400 memory devices.
QBM-800 Modules based on DDRI-400 devices won't be available until the second half of 2003. By that time, DDR-II may be gaining popularity. Hopefully, QDM won't go down in history as a good idea, that was too late too market.
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