Intel Socket 478: The Complete CPU List

This table lists every production processor Intel released for Socket 478 (mPGA478B), from the first Willamette Pentium 4 of 2001 to the last Prescott and Celeron D chips, plus the laptop CPUs built for the same socket. Use the filters to narrow it down by family, core, FSB or TDP, or type a model number or an sSpec code into the search box.

Four cores, one socket

Socket 478 lasted from 2001 to 2006 and went through four NetBurst cores. Two chips with the same clock can perform very differently, so the core matters more than the GHz figure.

• Willamette (180 nm). The first Pentium 4: 256 KB of L2, a 400 MT/s bus and high power draw for its speed. A good Tualatin Pentium III keeps up with the slower models. The Celeron 1.7 and 1.8 are Willamette chips cut down to 128 KB of cache.
• Northwood (130 nm). The best core for this socket. L2 doubled to 512 KB, it runs cooler than the cores before and after it, and it overclocks well. It shipped with 400, 533 and 800 MT/s bus, and the 800 MT/s models plus the 3.06 GHz have Hyper-Threading.
• Gallatin (130 nm). A Northwood with 2 MB of L3 cache taken from the Xeon MP, sold as the Pentium 4 Extreme Edition 3.2 and 3.4. Fast and rare, so today it is mostly a collector’s item.
• Prescott (90 nm). 1 MB of L2, SSE3 and a much longer pipeline. At the same clock it is rarely faster than Northwood, and it runs hotter. On Socket 478 it was sold as the 2.4A–2.8A (533 MT/s, no HT) and the 2.8E–3.4E (800 MT/s, HT). The Celeron D is a Prescott with 256 KB of cache.

What the letters mean

Before processor numbers arrived with LGA775, Intel told models with the same clock apart by a letter. The catch is that one letter can mean two different chips:

Many models, such as the 2.26, 2.53, 2.66, 2.8 and 3.06, have no letter at all. The reliable way to identify a chip is the marking on the heat spreader: a line like 2.80GHZ/512/800 gives the clock, L2 size and FSB, and the code starting with SL is the sSpec. Type that code into the search box above.

Will it run in my board?

Every chip in the list fits the same socket, but the board decides whether it works:

• FSB. The chipset has to support the CPU’s bus speed. The original i845 and i850 stop at 400 MT/s, the 845E/G/GE/PE and 850E add 533 MT/s, and 800 MT/s needs an i848P, i865PE/G/GV or i875P, or a comparable SiS or VIA chipset. Multipliers are locked, so a CPU on a slower bus than it was designed for runs well below its rated clock, if it starts at all.
• Prescott support. Prescott chips and the Celeron D need a board with a VRD 10 power design and a BIOS that knows them. Plenty of i845 and early i865 boards never got either, so check the board’s CPU support list before buying an A, an E or a Celeron D.
• BIOS. Northwood chips often need a BIOS update on boards designed for Willamette, and the late G1-stepping Prescotts from 2006 need a BIOS that includes their microcode.
• Hyper-Threading. HT only works when the chipset, BIOS and operating system all support it. On older boards an HT chip usually still runs, just with HT disabled.

Moving up to LGA775 instead? Our LGA775 CPU list covers that socket the same way.

Laptop CPUs in a desktop board

The Pentium 4-M, Mobile Pentium 4 and Mobile Celeron use the same mPGA478B socket, so they physically fit a desktop board. Whether they work depends on the BIOS: many i845 and i865 boards run them, some won’t boot, and boards without SpeedStep support may leave a Pentium 4-M at its low battery multiplier, which means 1.2 GHz. The Pentium 4-M and Mobile Celeron have no heat spreader, so take care when mounting the cooler. The reason to bother is power: a Pentium 4-M 2.6 is rated at 35 W, a little over half of a desktop Northwood at the same clock (62.6 W).

Not every laptop chip with “478” in its description fits. The Pentium M and Celeron M (Socket 479) and the Tualatin-based Mobile Pentium III and Mobile Celeron use a different pinout and won’t work in a Socket 478 board.

Which CPU to choose

• Best overall: Pentium 4 3.0C, 3.2C or 3.4C. They need an 800 MT/s board, run cooler than a Prescott at the same clock and have HT. The 2.4C–2.8C cost less and became famous overclockers: on a good i865PE or i875P board many reach 3 GHz or more by raising the FSB.
• 533 MT/s board: the 3.06 is the fastest desktop Northwood for this bus and the only one with HT. The Prescott 2.8A has more cache but is no faster in practice.
• 400 MT/s board: look for a Northwood 2.4–2.6, or the rare 2.8 with a 400 MT/s bus. Skip the Willamettes.
• Prescott A and E: worth it only when cheap. They draw more power (the 3.2E and 3.4E are rated at up to 103 W) for about the speed of a Northwood C.
• Celeron: the old Celeron with 128 KB of L2 is slow even next to a Pentium 4 2.0A. A Celeron D is clearly better, but a used Northwood Pentium 4 usually costs about the same.
• Extreme Edition: the fastest chips for the socket, but prices reflect collector interest more than performance.

When overclocking a Northwood, keep the core voltage modest. Chips that run at high voltage for long periods can degrade and die, a problem enthusiasts called Sudden Northwood Death Syndrome.

Building an AMD machine from the same years instead? Our Socket 939 CPU list covers the Athlon 64, X2 and Opteron.

FAQ

Can a Socket 478 CPU run 64-bit software?

No retail Socket 478 processor supports 64-bit. The only known exceptions are two E0-stepping Prescotts, SL7QB (3.2 GHz) and SL7Q8 (3.4 GHz), which Intel made for IBM servers and never sold at retail.

What is the newest Windows that runs on Socket 478?

Windows 8 and later require the NX (Execute Disable) bit, which retail Socket 478 chips lack, so 32-bit Windows 7 is effectively the last version that installs. Linux distributions that still ship 32-bit builds are the other option.