VIA Technologies Inc is gathering chip manufacturers behind its PC133 and PC266 double-data rate (DDR) synchronous DRAM specifications. The Taiwanese PC chipset designer has brought together a dozen vendors including IBM Corp, NEC Corp, Hitachi Corp and Siemens AG’s Infineon Technologies Group to promote the PC133 specification at conferences across South-East Asia. The companies are pushing PC133 as a low cost alternative to the Intel Corp-backed Rambus specification. PC133 is also seen as a bridge from the current PC100 specification to double data rate chips, dubbed PC266.
The key issues in choosing between PC133 and Rambus concern cost, chip compatibility and availability. PC133-compatible components are expected to be available in May, with PC266 components to follow in the third quarter. Delivery of Intel’s ‘Camino’ Rambus chipset has been delayed until September and commercial volumes will not be available until the end of the year. Rambus DRAM boards are likely to be 30% to 50% more expensive than 133MHz SDRAM boards, at least in the short term. But 133MHz chips will in turn be more expensive than the 100MHz chips now in common usage. Intel said that it will not support the PC133/266 chips, except for specific applications such as graphics boards.
On paper, the Rambus chips are clearly technically superior than either the PC133 specification or double data rate chips. Rambus is a memory subsystem that promises to transfer up to 1.6 billion bytes per second. The subsystem consists of the RAM, the RAM controller, and the path connecting RAM to the microprocessor and devices in the computer that use it. Rambus chips are expected to run at clock speeds of up to 800MHz.
Double Data Rate SDRAM can theoretically improve RAM speed to at least 200 MHz. It activates output on both the rising and falling edge of the system clock rather than on just the rising edge, potentially doubling output. PC133 is an upgrade of the PC100 specification with a synchronized system bus speed of 133MHz. However, while the Rambus looks like the faster chip on paper, there are issues with latency. Data transfer delays at the chip level are worse than on current fast RDRAM chips and some industry watchers question how much of a performance benefit Rambus will bring.
