Same Thing, Just Faster
Physical Interface: 242-contact Slot-A
Bus Interface: EV6 200MHz
0.18 micron process
L1 cache: 128KB, full core speed (850MHz)
L2 cache: 512KB, 2/5 core speed (340MHz)
There's not much we can say about this processor. We've already covered the main points in our original K7 reviews, and the Athlon 850 isn't much different from the 800.
Like the Athlon 800, the Athlon 850 is based on the K75 core, and sports 512KB of external L2 cache. The smaller 0.18 process lowers power requirements and heat, raises processor speeds, and allows AMD to fit more chips on each wafer. The L2 cache runs at 2/5 of the core processor speed which translates to 340MHz. The old Katmai Pentium III processors also had 512KB external L2 caches that ran at half the core speed. The newer Coppermine Pentium III processors halved the amount of L2 cache to 256KB and moved it onto the processor die where it is able to run at full core speed. The Coppermine made up for the smaller size with speed, and benchmarks show that the on-die cache is responsible for a significant increase in performance.
Fortunately, AMD is preparing to release Athlon processors with fully integrated, on-die L2 caches. After the L2 cache is moved on-die, AMD will shift away from Slot-A in favor of the new Socket A processor format. Having external SRAM chips for the L2 cache necessitated the cartridge format, but moving the L2 cache on-die will allow AMD to return to the cheaper socket format. Intel is also moving back to the socket format for the same reason. Pentium III processors are currently available in Slot-1 and FC-PGA form, but Intel plans on moving over to FC-PGA completely.
The Athlon uses the 200MHz Alpha EV6 bus which is a point-to-point bus where system components such as the system memory and CPU have their own exclusive channels to the chipset. Intel's P6 bus has all the system components on a single 100MHz front side bus. While point-to-point is an advantage for multiple processor systems, we're still waiting for that multiprocessor capable Athlon system.