LJ Archive

Pentiums and Non-Pentiums

Phil Hughes

Issue #11, March 1995

Scared of Pentiums? Looking for an alternative while you are waiting for the Alpha port? There are choices.

We just went through the “Pentiums don't always divide correctly” fiasco. This got a lot of people talking about Linux ports to other hardware such as the PowerPC and the DEC Alpha. While these ports are a good idea and are progressing, there are also some alternatives to Intel's Pentium chip that will run the same code.

The first of these Non-Pentiums is the K5 from Advanced Micro Devices (AMD). This chip promises pin-for-pin compatibility with the Pentium and promises greater internal speed for the same clock rate. To accomplish this, the K5 decodes X86 instructions into internal, long-word instructions that have fixed fields and word lengths—a technique pioneered with the RISC architecture. Converting the variable-length, variable-format X86 instructions to this consistent format makes it possible for the hardware to schedule up to four instructions in one clock cycle. AMD claims this will make it possible for the K5 to offer sustained performance 30% greater than an Intel Pentium running at the same clock rate.

Another maker of a Non-Pentium is NexGen Microproducts with their Nx586 chip. The Nx586 uses a similar internal architecture to the AMD chip and claims a 10% speed improvement on integer arithmetic. The Nx586 lacks an on-board floating point unit, but the level-2 cache controller is on the CPU.

The third choice is the M1 from Cyrix Corporation. There are currently no details available on this chip but it is another chip designed to match the capabilities of the Pentium.

While all this is happening, Intel is also working on more models of the Pentium chip. For example, they have produced a power-managed 75MHz Pentium designed for notebooks.

It seems competition is good incentive for companies to produce better, more inexpensive chips. Maybe this time next year you will have to pick between a Pentium-based, K5 based, Alpha-based or PowerPC-based laptop running Linux, each for under $1000.

[Editorial note: I think he is dreaming, but I wouldn't complain, either.]

Phil Hughes is the publisher of Linux Journal.

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