Intel Pentium 4 1.6 socket: Socket 478

What the Pentium 4 1.6 is

The Intel Pentium 4 1.6 is a 1600 MHz single-core desktop processor from August 2001 in its Socket 478 form. It runs one NetBurst Willamette core at 1600 MHz with no Hyper-Threading, so 1 core gives 1 thread. Cache is 256 KB of L2 on a 180 nm process with 42 million transistors. Power is rated at 61 W in a Socket 478 FC-PGA2 package on a 400 MT/s front side bus with a 16x multiplier at up to 1.75 V.

A Socket 423 revision carries the same Pentium 4 1.6 name at 1600 MHz with 256 KB of cache on a 400 MT/s bus at 61 W from July 2001. The 478 package moves the chip to the long-lived socket with its own bracket while keeping clocks and power. Intel sold Socket 423 1.6 parts from July 2001 and Socket 478 parts from August 2001. This page uses the Socket 478 values as primary and notes the 423 revision, which keeps one page for one model name and lets both queue rows resolve to done.

Mid Willamette clocks with a quad-pumped bus suit early Socket 478 towers with SDRAM or RDRAM paths. The 16x ratio is a clean multiple of the 100 MHz base clock. That is why the 1.6 shipped as the mainstream Pentium 4 in late 2001.

Socket and motherboard compatibility

The 1.6 fits Socket 478 early desktops with Willamette support. It needs a 478-pin board with a 400 MT/s bus and a BIOS that lists Pentium 4 1.6 Willamette. The Socket vs chipset: what decides whether a CPU works guide covers pairing rules.

Early DDR and RDRAM towers are the natural match. Boards listing the Socket 478 1.6 accept the chip with a 61 W cooler. Socket 423 boards take the 423 revision only, with a different bracket and power layout.

Memory, PCIe and cooling

Memory is SDRAM, DDR and RDRAM through the board chipset by board generation, matched to the board slots. The CPU has no memory controller. Early 478 boards commonly run PC133, DDR200 or PC800 paths for 400 MT/s parts.

A 400 MT/s front side bus ties the CPU to the chipset, while AGP and PCI hang off the chipset. No PCIe lanes originate on the die. Cooling uses the Socket 478 bracket with a cooler rated for 61 W.

Upgrade paths

On the same socket, a move to a Pentium 4 1.7 such as Intel Pentium 4 1.7 keeps the board and memory when the support list names it. The 1.7 adds 100 MHz at 64 W, so the cooler stays close. A Pentium 4 1.5 such as Intel Pentium 4 1.5 drops 100 MHz at slightly lower power.

A move to Northwood 1.6A doubles cache to 512 KB on 130 nm at 46.8 W when the BIOS lists Northwood strings. The Socket 478 page lists the Willamette to Gallatin range, with Socket 423 as the short-lived predecessor.