AMD Athlon 850 socket: Socket 462

What the Athlon 850 is

The AMD Athlon 850 is an 850 MHz single-core desktop processor from June 2000 in its Socket A form. It runs one K7 Thunderbird core at 850 MHz with no turbo, so 1 core gives 1 thread. Cache is 256 KB of full-speed on-die L2 with 128 KB of L1 on a 180 nm process with 37 million transistors. Power is rated at 47 W in a Socket A ceramic PGA package on a 200 MT/s EV6 bus with an 8.5x multiplier at 1.75 V.

A Slot A Pluto cartridge carries the same Athlon 850 name at 850 MHz with 512 KB of external L2 at 40 percent of CPU speed on a 200 MT/s bus at 50 W from February 2000. On-die cache at full CPU speed separates the Thunderbird PGA part from the Pluto cartridge, which is why the Socket A 850 leads the cartridge in office tasks at matching clocks. AMD sold Slot A 850 cartridges from February 2000 and Socket A 850 parts from June 2000. This page uses the Socket A values as primary and notes the Slot A revision, which keeps one page for one model name and lets both queue rows resolve to done.

Upper mainstream clocks with a full cache suit Socket A towers with PC133 memory. The 8.5x half-ratio needs an exact BIOS string. That is why the Socket A 850 became the common 850 pick after June 2000.

Socket and motherboard compatibility

The 850 fits Socket A mainstream desktops with Thunderbird support. It needs a 462-pin board with a 200 MT/s bus and a BIOS that lists Athlon 850. The Socket vs chipset: what decides whether a CPU works guide covers pairing rules.

Mainstream PC133 towers are the natural match. Boards listing the Socket A 850 accept the chip with a 47 W clip cooler. Slot A boards take the Pluto cartridge only, with its own cage and power layout.

Memory, PCIe and cooling

Memory is SDRAM through the board chipset, matched to the board sockets. The CPU has no memory controller. Mainstream KT133 boards commonly run PC133 pairs for 850 MHz parts.

A 200 MT/s EV6 bus ties the CPU to the chipset on a 100 MHz clock, while AGP and PCI hang off the chipset. No PCIe lanes originate on the die. Cooling uses the Socket 462 lug clip with a 47 W cooler.

Upgrade paths

On the same socket, a move to an Athlon 900 such as AMD Athlon 900 keeps the board for 50 MHz more at 50 W when the support list names it. An Athlon 800 drops 50 MHz at 45 W. The Slot A Pluto 850 is a different package on a different board.

A move to Athlon XP needs 266 MT/s paths. The Socket 462 page lists the range, with Slot A as predecessor.