Intel Pentium III 866, 850

Pentium III 866 Specifications

·        29 million transistor 0.18-micron Coppermine core

·        866MHz clock speed – 6.5x clock multiplier

·        32KB on-die L1 cache running at core speed

·        256-bit Advanced Transfer Cache - 256KB on-die L2 cache running at core speed

·        Advanced System Buffering

·        242-pin Slot-1 GTL+ CPU interface running at 133MHz

·        1.65v core voltage

The 833MHz Pentium III is not any different from the rest of the Pentium III line; it is based on the 0.18-micron Coppermine core and actually uses the same stepping (cA2) of the core as the previous Pentium IIIs with the exception of the 1GHz Pentium III, which is using a new core stepping required to hit the magical 1000MHz clock speed. 

The 866MHz chips are still using the 1.65v core voltage that is standard for all Pentium III processors with the exception of the lone 1GHz ranger that uses an increased 1.70v to, once again, hit the 1GHz clock speed. 

If you’re not familiar with some of the features the Coppermine core offers, the two biggest and most talked about benefits of this core are the Advanced Transfer Cache (ATC) and the Advanced System Buffering (ASB). 

The ATC on the Pentium III is just the fancy name for the on-die 256KB L2 cache.  Keep in mind that the Pentium III isn’t just a Celeron with twice as much cache and SSE, the L2 cache bus has been increased from the 64-bit bus width on the older Pentium III and Celeron processors to 256-bits wide.  The ATC also refers to the 8-way associativity of the 256KB L2 cache on the Coppermine (compared to the 4-way associative L2 cache on the old Pentium III/Celeron). 

Because the 256KB of L2 cache is on-die, the transistor count of the Pentium III is increased tremendously over the 9.5 million transistors that made up the original Pentium III (Katmai) core.  The 256KB L2 adds about 19 to 20 million transistors, putting the total transistor count of the Coppermine at approximately 29 million transistors. 

Advanced System Buffering is a simple term that represents the increase in buffers the Pentium III Coppermine offers over the previous generation of processors, including the Katmai based Pentium IIIs.  If you are interested in specifics, there are now 6 fill buffers, 8 bus queue entries, and 4 writeback buffers (up from 4, 4, and 1 respectively).  These three optimizations all help to take advantage of the 1.06GB/s bandwidth offered by the 133MHz FSB. 

Pentium III 850 Specifications

·        29 million transistor 0.18-micron Coppermine core

·        850MHz clock speed – 8.5x clock multiplier

·        32KB on-die L1 cache running at core speed

·        256-bit Advanced Transfer Cache - 256KB on-die L2 cache running at core speed

·        Advanced System Buffering

·        242-pin Slot-1 GTL+ CPU interface running at 100MHz

·        1.65v core voltage

The Pentium III 850 is identical to the other two chips with the exception of its specified FSB frequency, which is 100MHz instead of the 133MHz for the 866 chip. 

This makes the Pentium III 850 the ideal solution for your BX boards if you still haven’t migrated to a 133MHz FSB motherboard platform which, judging by the incredible cost of RDRAM and the just recent availability of good VIA 133A boards, we can’t really blame you for. 

Unfortunately, as of the time of publication, there were no BIOS updates for any of the boards we had in lab that would enable the 8.5x clock multiplier required by the Pentium III 850.  While this shouldn’t be a problem for most users since your CPU will feature a locked 8.5x multiplier, our test sample did not feature a locked multiplier and thus we were unable to run the 850MHz tests. 

We will provide an update as soon as we receive a BIOS update from the motherboard manufacturers that enables the 8.5x clock multiplier.