Fed up with hearing about Digital Equipment Corp’s gigahertz vaporware, IBM Corp has decided to trumpet a microprocessor developed by its Austin research lab using conventional CMOS techniques which is already operating at 1,100Mhz, plus the first conventional CPU – a PowerPC 750 – built using its new copper- based manufacturing process. IBM’s 1,100Mhz part dissipates 6.3 watts of power compared with DEC’s 600MHz Alpha 21264 which draws some 60 watts. But 21264 has 15.3 million transistors and IBM’s chip, which runs a subset of the PowerPC instruction set and is dubbed Guts (internally), has just one million gates and lacks both a floating point unit and memory subsystem. The Guts mechanisms IBM has patented are expected to feature in next- generation IBM Microelectronics products although the chip itself, which is built in IBM’s 0.25 micron CMOS 6X process, is purely experimental. What’s important are circuitry and architecture innovations which essentially reduce the number of operations that must be carried out by combing or parallelizing certain tasks, thereby enabling the chip to run quicker. Intel Corp and Hewlett-Packard Co have made extensive use of parallelizing techniques in their next-generation IA-64 instruction set. IBM says transistor placement on the die has been optimized; addition and rotation operations have been combined on a single circuit; the number of stages through which signals must pass has been reduced; the way the timing signal, the clock, is distributed has been optimized; and that testing can be done at speeds that are a fraction of the chip’s operating frequency. IBM’s Austin researchers say they have a floating point unit and memory subsystem under development. IBM expects the layout techniques to be applied to a new generation of chips produced using a new material process, the six-layer metal CMOS 7S copper manufacturing technique announced last year. IBM says it has created an prototype version of its existing PowerPC 750 RISC running at 480MHz in CMOS 7S that offers 20% greater performance than the regular CMOS 6S 750 device. IBM says the use of copper in the 0.2m process produced a 30% reduction in delays. Along with custom ASICs, PowerPC chips – including versions for AS/400 and S/390 – will be among the first products to be manufactured using CMOS 7S, which enables smaller and faster devices to be integrated on to the wafer. First products are expected towards the end of this year or early 1999. IBM says the prototype PowerPC 750 could be pushed to speeds of 1GHz or more.
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