Intel Pentium 4 HT 3.40 socket: Socket 478

What the Pentium 4 HT 3.40 is

The Intel Pentium 4 HT 3.40 is a 3.4 GHz single-core desktop processor with Hyper-Threading from February 2004. It runs one NetBurst core at 3.4 GHz with no turbo, so 1 core gives 2 threads through Hyper-Threading. Cache is 512 KB of L2 with 8 KB of L1 data and 12K micro-op trace cache on a 130 nm process. Power is rated at 89 W in a Socket 478 package with part number RK80532PG096512.

The 3.40 tops the Northwood HT line on Socket 478, using an 800 MT/s front side bus from a 200 MHz clock with a 17x multiplier at 1.25 V to 1.40 V. Intel sold it at 417 dollars in February 2004. The chip supports MMX, SSE and SSE2 with Hyper-Threading for two instruction streams. A Prescott 3.40E on 90 nm shares the model number range with 1 MB of cache and higher power, so codename separates the 130 nm Northwood from the 90 nm successor. This page covers the Northwood SL793 part.

Hyper-Threading shapes the use case. The second thread keeps execution units busy during cache misses, which helps office multitasking and media encoding on single-core towers. That is why Northwood HT parts carried a premium over non-HT Northwood parts at nearby clocks, even though both fit Socket 478 DDR boards.

Socket and motherboard compatibility

The Pentium 4 HT 3.40 fits Socket 478 desktops with DDR memory, an 800 MT/s front side bus and a BIOS that lists Northwood HT parts. It needs a 478-pin board with Hyper-Threading support, not an LGA 775 board with land contacts. The Socket vs chipset: what decides whether a CPU works guide covers pairing rules.

Performance DDR towers with AGP graphics are the natural match. Intel 865 and 875 series chipsets with DDR slots and 800 MT/s support accept the chip with a cooler rated for 89 W. Older 533 MT/s boards need a chipset and BIOS check for 800 MT/s operation. Forcing the chip into LGA 775 can damage contacts.

Memory, PCIe and cooling

Memory is DDR through the board chipset, with single or dual channel operation set by the chipset. Boards take DDR modules matched to the 800 MT/s bus, with the chipset setting timing and capacity. The CPU has no memory controller.

No PCIe lanes come from the processor. An 800 MT/s front side bus ties the CPU to the chipset, while AGP 8x handles graphics and PCI slots take other cards on Socket 478 boards. Cooling uses the Socket 478 retention bracket with four holes in a 60 mm by 75 mm rectangle and a heatsink rated for 89 W. Fresh paste and normal case airflow keep temperatures stable at 3.4 GHz.

Upgrade paths

On Socket 478 the nearby steps are the Pentium 4 HT 3.20 at 3.2 GHz with the same 512 KB and power class, and Prescott 3.40E parts at the same clocks with 1 MB of cache where listed. Pentium 4 EE 3.40 Gallatin parts with 2 MB of L3 cache offer a larger cache step on the same socket. Beyond Socket 478 a move to LGA 775 needs a new board with DDR or DDR2 memory, with Prescott 550 parts as successors. The 3.40 lifts with the lever, so swaps need no solder work.