Intel 80860 RISC Processor

关于 Intel 80860

Intel i860 或 Intel 80860 推出于 1989 年 2 月 27 日。Intel 的第一个超标量处理器， RISC32/64 位架构，管线的特性对于程序设计师而言非常显而易见，使用于 Intel Paragon 巨型平行超级电脑。RISC 为一种处理器架构，与传统的复杂指令集（CISC）不同，RISC 指令格式统一、种类少，容易学习、设计与开发程序。此款处理器的浮点能力大于整数运算。RISC 微处理器当初通常用于建造超级电脑。在 1993 年前后，英特尔 Paragon 超级电脑就是由一连串 i860 所组成的，曾经一度为当时世界上最快的超级电脑。现在几乎新一代的微处理器都是使用 RISC 架构。x86 系列是目前世界上唯一还在生产的 CISC 架构的微处理器。

Introduction

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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