AMD Athlon 850

The smoke has cleared, the battlefield remains deserted and some unclear points have finally come into focus.  The end of 1999 was a very unusual time for the CPU industry; we were originally told that the market would have to wait until 2000 to see anything faster than 700MHz from AMD and anything faster than 733MHz from Intel.

But in a professional version of the classic, ‘mine’s bigger’, competition, Intel and AMD accelerated both of their roadmaps and began announcing processors at an incredible rate.  It all started with the announcement of the Pentium III 733, which caused Compaq, one of the leading OEMs that use Athlon CPUs to influence AMD into releasing the 750MHz version of the Athlon simply in order to have a higher clock speed offering than Intel.  Intel’s response was the release of the Pentium III at 750MHz in addition to two other processors, an 800MHz Pentium III using the 133MHz FSB and an 800MHz Pentium III using the 100MHz FSB.  On the same day that Intel made those three introductions, AMD responded with their very own Athlon 800, once again because of increasing pressure from their faithful OEMs.

This time around, in anticipation of Intel’s upcoming annual Developer’s Forum (IDF) in Palm Springs, CA, AMD has pushed for the release of the next speed grade of their Athlon CPU.  Now running at 850MHz, the Athlon’s K75 core has yet another clock speed title under its belt.  Originally intended to be released on the 14^th of February, the Athlon 850’s release was sped up, once again by OEM influences, to a few days earlier just in case Intel decided to go ahead and release their higher clock speed Pentium IIIs at IDF.

·22 million transistor AMD K75 0.18-micron core

·850MHz clock speed – 8.5x clock multiplier

·128KB on-die L1 cache running at core speed

·512KB external on-card L2 cache running at 2/5 core speed (340MHz)

·242-pin Slot-A EV6 CPU Interface running at 100MHz DDR (effectively 200MHz)

·1.70v core voltage

As you can see, the Athlon 850 is just like the 750 and 800MHz in that it features a 2/5 L2 cache divider.  All of the Athlon CPUs slower than 750MHz feature a 1/2 L2 cache divider instead, meaning that the Athlon 700 still has a faster L2 cache (700MHz * 1/2 = 350MHz) than the Athlon 850 (850MHz * 2/5 = 340MHz), but because of the clock speed increase the Athlon 850 will still perform better than the older 700. 

The Athlon 850 is the third chip to initially use the K75 core; however, all new Athlon CPUs are being manufactured using the new 0.18-micron core.  The benefits of the 0.18-micron die shrink include lower power requirements and lower heat dissipation figures.  For example, a 0.25-micron (K7 core) Athlon 650 requires more power at 54W than a 0.18-micron (K75 core) Athlon 800 at 48W.  Unfortunately, the Athlon at 850 should require a little over 50W of power making it the highest current generation desktop x86 processor in terms of power consumption. 

In an attempt to increase the yields on the higher clock speed Athlons, the 850 is the first Athlon to run at the increased 1.70v core voltage setting.  All of the other Athlons run at 1.60v, by bumping the core voltage around 6% AMD can guarantee stable operation at 850MHz and open the path for 900MHz+ Athlon CPUs.