AMD K6-3 Review: Part 2

by Anand Lal Shimpi on December 25, 1998 12:38 AM EST

The Shot Heard Around the World

Approximately two months before AMD's official announcement of the K6-3 processor, the cat was let out of the bag and the upcoming processor's performance was revealed here on AnandTech.  The benchmarks the K6-3 produced at this early of a stage in its production managed to topple any lead Intel currently had over the rest of the market, however what good is an AMD performance lead now when the processor is months away from being released?  Will Intel have something prepared in response to the K6-3?  How well does the K6-3 perform without the benefit of a large L3 cache?   What motherboards can be recommended for use with the K6-3 next year?  One thing is for sure, although the K6-3 may not hold the glorious lead it initially illustrated over the competition in AnandTech's initial coverage of the chip, it is still the only true performance upgrade path for a Super7 user not looking to purchase a new motherboard.

100MHz FSB: A Temporary Solution

One of the biggest advantages the Pentium II offered over the competitor was its high speed L2 cache.  By deriving the speed of the L2 cache on the Pentium II's processor card from the clock speed of the processor itself, Intel made sure that the Pentium II's performance increase to clock speed increase didn't experience any sort of diminishing returns.  On the other side of things, the Socket-7 market was quickly dying due to the inability of the 66MHz Front Side Bus (FSB), the speed which the L2 cache also ran at, to compete in the much more aggressive world introduced by the Pentium II. 

The temporary solution was the advent of the Super7 extension of the Socket-7 platform, pushed solely by AMD, the Super7 design brought two critical wins to the socket-7 community: 1) AGP support, something which became more of an accepted standard with the Super7 platform although it was available prior to the release; and 2) the 100MHz FSB, a 50% increase in the frequency of the L2 cache on socket-7 systems, and a minimum of a 10% boost in overall system performance due to the increased L2 cache performance.  The latter was an incredible performance winner for socket-7 advocates at the time, since even the Pentium II 333's 166MHz L2 cache was threatened by the presence of a killer AMD + 100MHz FSB combo.  Unfortunately, for those users that were promised a true upgrade path for their older socket-7 motherboards, the first chip to officially support the 100MHz FSB, the K6-2, required that setting in order to achieve the level of performance AMD had promised.  Those with older socket-7 motherboards were left to either run their K6-2's at the standard 66MHz FSB, or forced to purchase new Super7 motherboards to receive the benefits they were promised. 

As both the K6-2 and the Pentium II rose in clock speed, the performance gap between the two processors began to grow to a much more noticeable separation, simply because the K6-2's L2 cache (located off chip, on the motherboard) was locked at that 100MHz FSB frequency (in some cases 112MHz depending on whether or not you overclocked the chip), and the Pentium II's L2 cache had already broken the 200MHz barrier with the Pentium II 450.  Although the 100MHz FSB was a solution to the competitive performance problem AMD faced in the early part of 1998, in 1999, that solution simply won't cut it. 

As mentioned in the original K6-3 Review, the key to the K6-3's performance is it's on-chip L2 cache running at clock speed ala the Intel Celeron A, this quickly avoids the temporary solution the 100MHz FSB provided by allowing the speed of the L2 cache to rise directly with the speed of the processor, removing any bottlenecks the L2 cache performance would be able to offer for a K6-3 system.  At the same time, by removing the performance dependency of the L2 cache on the system's FSB frequency, AMD also managed to remove another problem older socket-7 users faced, the need for the 100MHz FSB.

100MHz FSB: No Longer Necessary?
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