AMD K6 released April 2, 1997

AMD launched its K6 microprocessor on April 2, 1997. It was a competitor for Intel’s Pentium II CPU, but unlike the Pentium II, it plugged into the previous-generation Pentium socket. Being less expensive than a Pentium II and using less expensive motherboards, the AMD K6 allowed for much less expensive PCs. The K6 competed successfully with Intel.

The K6 cost between $244 and $469 at launch time. That undercut Intel by about 35%.

The AMD K6 architecture

The AMD K6 is a superscalar Pentium-class microprocessor, manufactured by AMD, replacing the AMD K5 in its product line. After the K5’s relative disappointment, the K6’s immediate success surprised almost everyone. It allowed AMD to move into the middle of the market after years of making entry-level CPUs like the AMD 5×86.

The AMD K6 is based on the Nx686 microprocessor that NexGen was designing when AMD acquired it in 1996. Despite the name implying a design evolving from the K5, and some similarities in the way it operated, the K6 is a totally different design. NexGen’s design team designed the K6.

The K6 processor included a feedback dynamic instruction reordering mechanism, MMX instructions, and a floating-point unit. Like the AMD K5, Nx586, and Nx686 before it, the K6 translated x86 instructions on the fly into dynamic buffered sequences of micro-operations.

Intel’s response to the K6

The K6 put pressure on Intel, who wanted to move away from Socket 7 to a proprietary, high-performance bus. Intel responded with its first-generation Celeron at 266 MHz, which it could price at K6 levels, but clock for clock couldn’t keep pace because Intel just lopped off the L2 cache to cut costs. The Mendocino-based Celeron, which took time to develop because it had a small amount of on-die L2 cache, fared much better.

The price/performance combination of the K6 forced Intel to produce CPUs it didn’t want to produce. The big money for Intel was in its highest-end CPUs, but Intel couldn’t afford to completely cede the low end of the market to AMD.

AMD K6 performance

Manufactured at AMD’s Fab 25 in Austin, AMD struggled to keep up with demand for the K6, which kept its prices higher than they otherwise would have been. This allowed Cyrix to undercut AMD at the low end of the market, but AMD’s ability to reach higher clock rates meant it was able to compete as a mid-market CPU with this generation. The K6’s floating point performance was closer to the Pentium MMX than to the Pentium II, so Intel’s top chip still had an edge. But for normal integer performance, AMD was just as fast as a Pentium II. If you weren’t playing 3D games, AMD provided much better value for money. If you were playing 3D games, you could close the difference by adding a 3DFX card like the Orchid Righteous 3D.

The K6 was originally launched in April 1997, running at speeds of 166 and 200 MHz and using a 66 MHz front side bus. It was followed by a 233 MHz version later in 1997. Initially, the AMD K6 processors used a Pentium II-based performance rating (PR2) to designate their speed. AMD later dropped the PR2 rating because the K6 was approximately the same speed clock for clock as a Pentium II. AMD wasn’t able to release a 266 MHz version until the second quarter of 1998, when AMD was able to move to the 0.25-micrometer manufacturing process. The lower voltage and higher multiplier of the 266 MHz and 300 MHz versions meant that it was not fully compatible with some earlier Socket 7 motherboards. The 300 MHz iteration, released May 1998, was AMD’s final K6.

A later variation of the K6 CPU, the AMD K6-2, added floating-point-based SIMD instructions, called 3DNow!, and used a 100 MHz front side bus.

Who sold it

Dell famously refused to use the AMD K6, but virtually every other large PC manufacturer, including Acer, Compaq, IBM, and Hewlett Packard, used the K6, at least in its consumer line. Business PCs remained largely Intel’s domain. But selling to large OEMs was a big boon for AMD, whose 386 and even 486 CPUs didn’t see widespread adoption in name brand PCs.

You may sometimes see reference to an IBM K6 CPU. AMD did have an arrangement with IBM to use its fabrication plants like Cyrix and Transmeta did, but never ended up exercising the deal. IBM used the AMD K6 in its Aptiva line, but negotiated the rights to call it an IBM K6, so some IBM ads and spec sheets from the period refer to an IBM K6 CPU. Although IBM had the rights to manufacture certain Intel designs or derivatives like the 486SLC2, and also manufactured CPUs for Cyrix, IBM did not manufacture the chips it called an IBM K6. IBM buying CPUs from AMD rather than using its half of the yield it received from Cyrix in its own PCs was a blow to Cyrix.

The cashflow AMD generated with the K6 family of CPUs made it possible to develop the very successful Athlon and subsequent CPUs, and make a big turnaround.

My AMD K6 stories

This is purely anecdotal, but the week the AMD K6 hit the market, I had my wisdom teeth extracted. The oral surgeon asked me what I did for a living. I said I worked in IT, and he asked, “Oh, so you must know something about those new AMD chips?” And then he proceeded to pump me for information on how the K6 compared to a Pentium II before putting me under. It’s possible he was just making conversation, but I came away with the impression that at least one oral surgeon in central Missouri was excited about AMD’s new CPU.

Also around that time, my future wife’s parents bought a Compaq Presario sporting a K6. When they upgraded, they passed that machine to her. That’s the computer she was using when we met. By then it was a bit underpowered, so I swapped in a faster motherboard for her not long after we met. But she and her parents got their money’s worth out of that K6.

Dave Farquhar

David Farquhar is a computer security professional, entrepreneur, and author. He has written professionally about computers since 1991, so he was writing about retro computers when they were still new. He has been working in IT professionally since 1994 and has specialized in vulnerability management since 2013. He holds Security+ and CISSP certifications. Today he blogs five times a week, mostly about retro computers and retro gaming covering the time period from 1975 to 2000.