IBM Corp says it has uniquely embedded cheap DRAM memory on to a single logic chip without compromising the function of either. IBM expects first commercial implementations of its system-on-a- chip technology will be in high-end communications gear produced by its own networking division and other datacoms customers it declined to identify. It believes the first single-chip cell phones using this technology will become available in 2001 and estimates adding DRAM memory to logic adds 25% to the cost of a chip. What the innovation will logically lead to, IBM says, is the replacement of large and expensive SRAM, currently used as the on-board cache on conventional microprocessors, with DRAM. It is ten times quicker to access on-board memory than if it is located elsewhere. IBM says the technique won’t be used to replace existing DRAM memory, however, and as much of the current debate about computer system design revolves around the time penalty (and software problems) associated with accessing remote memory sources, the technique is significant, it claims. Big Blue is not saying it’s the first to develop an integrated system-on- a-chip solution but is claims that using its 0.15 copper process it has been able to overcome problems that beset traditional designs. It’s the first technically and economically viable, implementation, it claims. Conventionally, logic is added to memory chips rather than visa versa. Memory leaves bumps on the chip surface and when wires for logic are laid down it is the logic functionality that tends to suffer. Even in other memory- on-logic implementations, affixing memory tends to cause obstructions, IBM claims. Its SA-27E can accommodate up to 24 million transistors and is claimed to offer eight times the processing ability and two to four times the memory found on a typical PC, although it says it clearly hasn’t reached the point where all of the functions of a computer have been integrated a single chip. In the first instance IBM is only using its copper wiring design, not its silicon-on-insulator technique, though it says there’s no reason why it couldn’t use SOI in future. It will manufacture third-party designs beginning in April and is working with EDA vendors such as Mentor Graphics to ensure the process is supported in their design applications. Current partner ST Microelectonics NV will both act as a second source for IBM and work with the company on developing systems-on-a-chip. ST Microelectronics has a range of system-on-a-chip designs for storage control. Some problems with embedding DRAM on logic include bandwidth constraints and providing access to embedded DRAM after a cache miss. NEC Corp and Hitachi Ltd have each outlined plans to provide embedded DRAM processes and ways to overcome these problems. Hitachi is reportedly touting an access optimizer traffic cop while NEC is to overhaul the way DRAM is operated.
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