SiS touts transition DIMMs

184-pin SDRAM to pave way for 184-pin DDR

Taiwan's Silicon Integrated Systems has launched its SDRAM-to-DDR transition memory scheme, designed to work with the Tualatin-supporting SiS635T chipset and its Athlon equivalent, the SiS735.

The memory technology, SDR/DDR Share Mode, is based on 184-pin DIMMs capable of holding PC-133 SDRAM or DDR memory. The DDR DIMM spec. is based on a 184-pin module. Regular SDRAM uses 168-pin modules.

Clearly there's an incompatibility. SiS believes the industry should move to 184-pin Share Mode DIMMs. Motherboard makers would use only DDR slots, knowing that 184-pin PC-133 SDRAMs can be used too.

The alternative would be to force mobo makers to design and implement either slots capable of working with both kinds of memory - or shipping boards with banks of SDRAM and DDR slots.

SiS' SDR/DDR Share Mode supporters Apacer (part of Acer Labs) and TwinMOS reckon that it will be easy for other DIMM makers to transfer 168-pin DIMM production to the 184-pin spec. "The 184-pin SDR DIMM is the JEDEC industry standard for memory chips," said a TwinMOS representative. "It is very easy for memory module makers to put into production."

How many will do so remains to be seen, however. At this stage, DDR and SDRAM are targeted at different sectors of the PC market, so it's questionable how much need there is and will be for transition products. SiS' argument is that "the high price sensitivity of the PC market makes integration [between old and new memory technologies] inevitable".

But the bottom line is that consumers will need to buy new memory, whether it's 184-pin SDRAM DIMMs to use until DDR becomes a necessary upgrade, or, by buying a DDR-based mobo, 184-pin DDR DIMMs to replace 168-pin modules. Either way, the punter pays out as they always have had to (SIMMs to DIMMs, PC-100 to PC-133, etc).

The advantage here is for mobo makers who can make one board fit multiple price points, but they'll only be tempted to do so if they can sell them, ie. if there's enough 184-pin SDRAM DIMMs out there for consumers and PC makers to be able to use to build complete systems. ®

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