News & Views / December 1995

AMD Acquires NexGen's Nx686

Tom R. Halfhill

AMD's surprise acquisition of NexGen should give a significant boost to both companies. NexGen will become a subsidiary of AMD and will continue designing new x86 microprocessors. NexGen's latest CPU, the Nx686, has been renamed the AMD-K6 and will be marketed as a sixth-generation competitor to Intel's Pentium Pro. AMD says it has halted its own K6 project and is reassigning that project's engineers to help NexGen finish the Nx686/K6. Their goal is to ship the CPU in late 1996, ramping up to volume production in 1997.

Thanks to the merger, AMD will manufacture the K6 at its new wafer-fabrication plant in Texas. Until now, NexGen was a so-called fabless company whose chips were manufactured by IBM Microelectronics. NexGen also stands to gain from AMD's superior marketing muscle and established customers.

AMD wins, too. In October, AMD admitted that its long-delayed K5 processor would be stalled another three months, pushing volume shipments back to late 1996. Meanwhile, AMD's own K6 project was falling behind schedule. By acquiring NexGen, AMD gets a nearly complete sixth-generation design and some breathing room to finish the K5, which will be positioned as a lower-cost alternative.

The new K6 introduces several improvements over NexGen's Nx586. It has an integrated FPU, better branch prediction, two x86 instruction decoders, more registers, larger caches, more execution units, and the ability to retire up to four instructions per cycle instead of three. Like its predecessor, it executes instructions speculatively and out of order.

Two important features of the Nx586 that won't be carried forward are an integrated cache controller and a dedicated I/O bus for the secondary cache. NexGen has decided to make the K6 pin-compatible with Intel's Pentiums. That means discarding the high-speed cache bus.

NexGen says that the K6 will debut at 180 MHz and will roughly match the performance of a similarly clocked Pentium Pro when running 32-bit software. However, NexGen also says the K6 will not suffer the Pentium Pro's loss of performance when running 16-bit code.

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