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AMD Athlon


AMD Athlon

Late November 1999 sees yet another addition to AMD's impressive Athlon processor line-up in the shape of the Athlon 750 MHz. Unlike other members of the Athlon family, the 750 has a number of differences which warrant attention.

The first main difference that the Athlon 750 brings, is that it is based upon the new K75 core unlike it's predecessors which are based upon the K7 core. The main feature of the K75 core is that it is manufactured using the new 0.18 μm process, wheras the K7 core uses the older 0.25 μm process. The 0.18 &um;m process allows AMD to shrink the 22 million transistor Athlon core from 184mm2 of the K7 down to 102mm2 of the K75 core. This will be significant as it will result in the Athlon requiring less power to operate, and subsequently will generate significantly less heat.

Eventually the K75 core will include 256Kb level 2 cache running at full clock speed, but this is scheduled to take place in H1 2000. For the time being the K75, as used in the Athlon 750, will feature 512 Kb level 2 cache running off-chip on the processor module.

The other significant difference with the Athlon 750 compared to it's predecessors is that it will run it's level 2 cache at a slower speed. Unlike Athlon's up to 700 MHz which all feature 1/2 speed level 2 cache, the Athlon 750 features a cache speed divider of only 1/25 processor speed. Wheras an Athlon 700 features 512 Kb level 2 cache running at 350 MHz, the Athlon 750 runs it's cache at a slower 300 MHz. This does hamper the Athlon 750's performance when running cache intensive operations, with many benchmarks on the Internet showing only a marginal increase in performance over the Athlon 700. This reduction in cache speed is necessary as AMD has found it increasingly difficult to source cache SRAM chips at speeds faster than 3ns. The 375 MHz requirement of 1/2 speed cache for the Athlon 750 would require 2.6ns SRAM chips, thus AMD decided to change the cache divider solve this problem.

Where the Athlon 750 does shine is in FPU intensive operations such as 3D Studio MAX and other rendering packages which can make use of it's fully pipelined FPU. The Athlon 750 does show impressive power in games too.

Athlon 750, the verdict.

Overall, the Athlon 750 is something of a mixed bag. Whilst it brings yet another clock speed increase to the table, and a new smaller core, it does have a slower cache. Whilst under many applications the reduced cache speed will not be apparent, it does show that the limits of module based cache is rapidly approaching, and the Athlon will need to move to a fully integrated level 2 cache similar to Intel's "Coppermine" Pentium III.

Where the Athlon does shine is in applications which can make use of it's sheer clock speed (750 MHz is fast!) and it's FPU architechture. If this is a priority to you, the Athlon 750 is a good bet.


Athlon 700.


Other AMD Pages: Athon review pages:


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© Copyright, Anthony Barrett 1999/2000.