Intel Pentium III Xeon 866 5V-12V socket: Slot 2

What the Pentium III Xeon 866 5V-12V is

The Intel Pentium III Xeon 866 5V-12V is an 866 MHz single-core server processor from April 2000. It runs one P6 Cascades core at 866 MHz with no Hyper-Threading, so 1 core gives 1 thread. Cache is 256 KB of full-speed L2 with 32 KB of L1 on a 180 nm process with 28 million transistors. Power is rated at 29.6 W in a Slot 2 SECC cartridge on a 133 MT/s front side bus with a 6.5x multiplier on the 5V-12V regulator path.

The 133 MT/s bus with a half-ratio multiplier gives the 866 balanced throughput on server boards, which is why it headed dual-processor workgroup servers in early 2000. Intel launched the Xeon 866 on April 10, 2000 at $826. The chip supports MMX, SSE and two-way SMP.

Mid server clocks with a fast bus suit Slot 2 workgroup boards with registered SDRAM. The 6.5x ratio needs an exact BIOS string. That is why the 866 5V-12V shipped in dual server boxes.

Socket and motherboard compatibility

The 866 5V-12V fits Slot 2 servers wired for 5V-12V Xeon regulation. It needs a 330-lead SC330 board with a 133 MT/s bus and a BIOS that lists the 5V-12V Xeon 866. The Socket vs chipset: what decides whether a CPU works guide covers pairing rules.

Dual workgroup servers are the natural match. Boards listing the 5V-12V string accept one or two cartridges with 29.6 W heatsinks each.

Memory, PCIe and cooling

Memory is registered ECC SDRAM through the server chipset, matched to the board sockets. The cartridge has no memory controller. Workgroup boards commonly run ECC pairs.

A 133 MT/s front side bus ties each cartridge to the chipset, while PCI hangs off the chipset. No PCIe lanes originate on the cartridge. Cooling uses SECC heatsinks on the retention cage.

Upgrade paths

On the same slot, a move to a Pentium III Xeon 866 2.8V such as Intel Pentium III Xeon 866 2.8V keeps clocks and cache while changing regulator path when the board stocks the other variant. A Xeon 800 5V-12V on the same list drops clocks with less cache.

A move to Foster Xeon needs Socket 603. The Slot 2 page lists the range for planning. Note: the queue row lists 25 W; this page uses the verified 29.6 W from the Xeon tables.