Making it clear once again that the challengers for Intel Corp’s iAPX-86 crown can do a whole lot more than simply clone Intel’s microprocessor, Cyrix Corp today releases details of its first pass at a microprocessor that is instruction set-compatible with the 80486, yet is a part Intel does not have in its armoury. At Spring Comdex on April 6 it plans to announce immediate availability of the Cx486SLC, a 25MHz microprocessor compatible with the 80486 yet with a 16-bit bus and the same pinout as Intel’s own 80386SX, so that manufacturers can build it into their existing 80386SX designs, and deliver a claimed 2.5 times improvement in performance over 25MHz 80386SX and 80386SL portable computers. It is also an original design, implementing a single-cycle pipeline with 16-bit hardware multiplier, optimised five-stage pipeline and tightly-coupled 1Kb instruction and data cache which uses two-way set associative, four byte line size architecture with 32-bit internal interface. This enables the cache to be accessed in parallel with other pipeline activity so that whenever a cache hit is made, it is two clock cycles faster than zero wait state external bus accesses. Internal memory is accessed with a 32-bit bus rather than the 16-bit external bus. The hardware multiplier is claimed to speed applications like graphics and handwriting recognition compared with the shift-add multiply function of other 80486 designs. The Richardson, Texas company says that power management features support 3V operation for a typical 600mW power drain against 2W at 5V and the fully static 0.8 micron design means that the part will operate right down to the point where the clock slows to a halt; there is also a suspend-resume feature that cuts power drain back to micro-Watts. It can be used with the company’s 87SLC maths co-processor. The 5V Cx486SLC-25 is $119 in 1,000-up quantities with deliveries starting next quarter, although samples are already out with designers. The price is expected to fall to below $100 in the third quarter, when a 33MHz version is planned to be available. Cyrix also says that it will soon announce a significant second-source agreement for fabrication of the part to meet the evident demand.
