Intel Xeon 3.6 socket: Socket 604

What the Xeon 3.6 is

The Intel Xeon 3.6 is the fastest single-core Irwindale for dual-socket servers, from February 2005. One NetBurst core runs at 3.6 GHz through an 18x multiplier on an 800 MT/s front side bus. Hyper-Threading is supported across the family, giving 2 threads from the single core, and a parts listing for sSpec SL7ZC confirms Hyper-Threading support with a single core. Tray sSpecs are SL7ZC and SL7ZJ under order number RK80546KG1042MM, and the boxed E-suffix part is sSpec SL8P3. The die is 90 nm.

Cache is 2 MB of on-die L2 with no L3 on the die. A parts listing for SL7ZC confirms the 3600 MHz frequency, the 800 MHz bus, the 18x bus to core ratio, the 2 MB L2, the 90 nm process, Socket 604, and the Micro-FCPGA package. Wikipedia records stepping N0 for the tray sSpecs and R0 for SL8P3.

The TDP picture has a genuine conflict and this page resolves it toward the per-SKU source. The SL7ZC parts listing gives 110 W with a 1.2875 V to 1.3875 V range, and Dell parts data for the same sSpec agrees at 110 W. Wikipedia leaves the 3.6 GHz TDP cell blank. Against that, one comparison site prints 135 W for a Xeon 3.6 entry without sSpec detail. The verified per-SKU value of 110 W is used here, with the conflict stated so board planners can double-check the CPU list.

Socket and motherboard compatibility

The socket is Socket 604, the 604-pin mPGA604 zero insertion force socket. As a DP part this chip is for boards with up to two sockets, the dual-processor topology Wikipedia assigns to Irwindale and that Intel's 2 MB Xeon datasheet confirms. It does not belong in four socket MP boards, which follow separate qualification even though the pins match.

Support is decided by the board vendor line by line. The CPU list must name SL7ZC, SL7ZJ, or SL8P3 as installed, the BIOS must carry the matching microcode, and regulation must cover a 110 W part in the 1.25 V to 1.388 V band. Multiplier behavior is locked on this SKU, which a comparison listing confirms, so no bus speed tricks can substitute for buying the right bin. The Socket vs chipset: what decides whether a CPU works guide covers the socket, chipset, and BIOS interplay.

A used purchase check is short. Match the printed sSpec to the board list, confirm the BIOS revision, and confirm the chassis airflow path in the board manual covers a dual 110 W population.

Memory, PCIe and cooling

Memory is a board matter here, and no opened source assigns a memory type to this exact SKU, so none is claimed. The server maker memory list for the exact board sets type, speed, rank discipline, slot order, and the capacity ceiling. Intel's DP datasheet for the 2 MB family describes board designs addressing up to 64 GB, but the number that counts is the one in the manual for the chassis on the bench.

An 800 MT/s front side bus joins the CPU to the server chipset, and every expansion slot descends from that chipset. Slot versions and lane behavior are board documentation topics. Console duties sit with board graphics or remote management hardware.

Cooling must match a 110 W dual-socket layout with vendor parts. The heatsink is the server maker component specified for the exact board and chassis, seated in the directed airflow the manual assumes. Because some lists print 135 W for this bin, keeping heatsinks rated for the verified 110 W value while confirming the board list is the balanced approach.

Upgrade paths

Inside the Irwindale line there is nowhere faster to go, since 3.6 GHz is the top single-core bin. The Intel Xeon 3.4, the Intel Xeon 3.2, and the Intel Xeon 3.0 give slower, cheaper, or cooler alternatives in the same socket with the same 2 MB L2 and 800 MT/s bus. Each is a board list and BIOS question, not a platform change.

The thread increase on this socket is the dual-core Paxville DP Intel Xeon 2.8, on boards whose BIOS lists it. Past Socket 604, newer Xeon generations need a new board, new memory, and a new thermal design.