Intel Xeon 2.8 socket: Socket 604

What the Xeon 2.8 is

The Intel Xeon 2.8 is the dual-core Paxville DP processor for two-socket servers, launched October 10, 2005. Two NetBurst cores share one 604-pin package, each running at 2.8 GHz through a 14x multiplier on an 800 MT/s front side bus. Hyper-Threading is documented for every Paxville DP model, so the two cores present 4 threads. The sSpec is SL8MA on stepping A0 with order number NE80551KG0724MM, and the process is 90 nm.

Cache is generous for its date: 2 MB of L2 per core, or 2x2 MB across the package, with ECC protection and no L3 on the die. Wikipedia records exactly this layout with the 800 MT/s bus, the 14x multiplier, the 135 W envelope, and the October 10, 2005 date. Intel's October 2005 datasheet for this processor confirms the 2 MB transfer cache per core, the 800 MHz bus, and the 604-pin FC-mPGA4 package in the mPGA604 socket.

Thread count needs one sentence of care. TechPowerUp tables list 2 threads for this SKU, counting physical cores only. Intel's datasheet states Hyper-Threading lets the single physical processor function as four logical processors, two per core, and Wikipedia documents Hyper-Threading on all Paxville DP models. This page therefore uses 4 threads with the disagreement explained, since the logical processor count is what the operating system sees.

Socket and motherboard compatibility

The chip fits Socket 604, the 604-pin mPGA604 zero insertion force socket. Intel's datasheet names the package as 604-pin FC-mPGA4 in a surface mount ZIF mPGA604 socket, which removes any doubt about the mechanical fit. As a DP part it is qualified for boards with up to two sockets, the dual-processor topology Wikipedia records for Paxville DP and that Intel confirms with scalability to two processors.

Board qualification is specific. The server board CPU list must name the 2.8 GHz Paxville DP or sSpec SL8MA, the BIOS must carry its microcode, and regulation and cooling must be rated for 135 W. Dual-socket boards built for single-core Nocona or Irwindale parts may share the socket yet lack the BIOS or power headroom for a dual-core 135 W chip. The Socket vs chipset: what decides whether a CPU works guide covers the socket, chipset, and BIOS interplay.

When evaluating a used board, check the CPU list entry first, then the BIOS revision, then the chassis airflow path for a dual 135 W population in the board manual.

Memory, PCIe and cooling

Memory flows through the server board, and TechPowerUp records ECC support with a dual-channel board memory bus for this SKU. Intel's datasheet describes board designs supporting up to 64 GB of physical memory, but the type, speed, rank rules, and ceiling for a given chassis come from the server maker memory list. Slot population order should follow the manual exactly on dual-socket boards.

An 800 MT/s front side bus ties the package to the server chipset, and expansion slots descend from that chipset. There is no integrated graphics and no on-die PCIe controller, so slot behavior and console output are board topics. These systems are normally administered headless or through board management hardware.

Thermal design centers on 135 W with vendor heatsinks. Intel's datasheet assumes Thermal Monitor operation in a server chassis with directed airflow, and the practical rule is the server maker heatsink specified for the exact board and chassis. Undersized cooling on a dual 135 W board pair invites throttling under sustained load.

Upgrade paths

The same-socket dual-core MP alternatives are the Paxville MP parts such as the Intel Xeon MP 7030 Dual-Core at 2.8 GHz and the Intel Xeon MP 7040 Dual-Core at 3.0 GHz, but they belong to multiprocessor board populations with their own qualification lists. A DP board that lists only this Paxville DP chip may not accept MP parts, so the board CPU list decides. Single-core Irwindale options such as the Intel Xeon 3.6 fit the same socket where fewer threads are acceptable.

Past Socket 604, the dual-core Dempsey generation already moves to a different socket, so any platform step beyond this one means a new board, new memory, and a new thermal plan.