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The Intel i860 Processor
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The i860 processor, modestly described by Intel as "a Cray on a Chip", achieved high levels of integer, floating point, and 3D graphics performance. The graphics unit was unique for its time. It was essentially a 64-bit integer unit using the FPU registers. It supported a number of commands for SIMD-like instructions in addition to basic 64-bit integer math. Experience with the i860 influenced the MMX functionality later added to Intel's Pentium processors. As a result of its architecture, the i860 could run certain graphics and floating point algorithms with exceptionally high speed, but its performance in general-purpose applications suffered and it was difficult to program efficiently.
At first the i860 was only used in a small number of Supercomputers like the iPSC/860 at Los Alamos National Laboratory. It also did see some use in the workstation world as a graphics accelerator. It was used, for instance, in the NeXT Dimension and some SGI graphics workstations.
The chip was released in two versions, the basic XR, and the XP. The XP added larger on-chip caches, support for external second level cache, faster buses, and hardware support for bus snooping, for cache consistency in multi-processor parallel computing systems. The XR ran at 25 or 40MHz, and a process shrink for the XP (from 1 micrometer to 0.8) bumped the XR to 40 and 50MHz. Both ran the same instruction set. |
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