Intel Pentium III Xeon 900 2.8V socket: Slot 2

What the Pentium III Xeon 900 2.8V is

The Intel Pentium III Xeon 900 2.8V is a 900 MHz single-core server processor from March 2001. It runs one P6 Cascades core at 900 MHz with no Hyper-Threading, so 1 core gives 1 thread. Cache is 2 MB of full-speed ECC L2 with 32 KB of L1 on a 180 nm process with 140 million transistors. Power is rated at 36 W in a Slot 2 SECC cartridge with part numbers SL4XY and SL5D3 on a 100 MT/s front side bus with a 9x multiplier at 2.8 V core.

The 2 MB full-speed cache with a dedicated cache bus separates Xeon cartridges from desktop Pentium III parts with 256 KB, which is why the 900 2.8V suits database servers despite modest clocks. Intel launched the Xeon 900 on March 21, 2001 with 2.8 V and 5V-12V regulator variants at $3692. The chip supports MMX, SSE and four-way SMP on server chipsets.

Server clocks with a large ECC cache and a 36 W envelope suit Slot 2 rack servers with registered SDRAM and PCI-X expansion. The cartridge thermal plate spreads heat across the server heatsink. That is why the 900 2.8V shipped in quad-capable database boxes.

Socket and motherboard compatibility

The 900 2.8V fits Slot 2 multiprocessor servers with Cascades Xeon support. It needs a 330-lead SC330 board with a 100 MT/s bus and a BIOS that lists the 2.8 V Xeon 900. The Socket vs chipset: what decides whether a CPU works guide covers pairing rules.

Quad-capable rack servers are the natural match. Boards listing SL4XY accept one to four cartridges with 36 W heatsinks each. The 2.8 V string matters because 5V-12V boards use a different regulator path for the same clocks.

Memory, PCIe and cooling

Memory is registered ECC SDRAM through the server chipset, matched to the board DIMM sockets. The cartridge has no memory controller, so the chipset sets ECC paths and speed. Quad 440GX boards commonly interleave ECC pairs across processor paths.

A 100 MT/s front side bus ties each cartridge to the chipset, while PCI-X hangs off the chipset. No PCIe lanes originate on the cartridge. Cooling uses SECC cartridge heatsinks locked to the retention cage with front-to-back server airflow.

Upgrade paths

On the same slot, a move to a Pentium III Xeon 900 5V-12V such as Intel Pentium III Xeon 900 5V-12V keeps clocks and cache while changing regulator path when the board stocks the other variant. The two strings share 900 MHz and 2 MB, so the swap is electrical rather than performance. A Xeon 866 on the same list drops clocks with less cache.

A move to Foster Xeon needs Socket 603 with a new board. The Slot 2 page lists the Cascades server range for planning.