Intel Pentium 4 1.9 socket: Socket 478

What the Pentium 4 1.9 is

The Intel Pentium 4 1.9 is a 1900 MHz single-core desktop processor from August 2001 in its Socket 478 form. It runs one NetBurst Willamette core at 1900 MHz with no Hyper-Threading, so 1 core gives 1 thread. Cache is 256 KB of L2 on a 180 nm process. Power is rated at 69 W in a Socket 478 FC-PGA2 package on a 400 MT/s front side bus with a 19x multiplier.

A Socket 423 revision carries the same Pentium 4 1.9 name at 1900 MHz with 256 KB of cache at 69 W from August 2001. Both packages launched the 1.9 together as the 423 run closed, which is rare among Willamette clocks. Intel sold both revisions in 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.

Near-2 GHz Willamette clocks with a 19x ratio suit late 423 and early 478 towers alike with RDRAM or DDR paths. The shared 69 W envelope keeps cooler choice identical across sockets. That is why the 1.9 shipped on both packages at once.

Socket and motherboard compatibility

The 1.9 fits Socket 478 late Willamette desktops with 1.9 support. It needs a 478-pin board with a 400 MT/s bus and a BIOS that lists Pentium 4 1.9 Willamette. The Socket vs chipset: what decides whether a CPU works guide covers pairing rules.

Late DDR and RDRAM towers are the natural match. Boards listing the Socket 478 1.9 accept the chip with a 69 W cooler. Socket 423 boards take the 423 revision with the 423 bracket.

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. Late boards commonly run DDR200 or PC800 paths for 1900 MHz 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 69 W.

Upgrade paths

On the same socket, a move to a Pentium 4 2.0 Willamette keeps the board when the support list names it. The 2.0 adds 100 MHz at higher power with the same bus. A Pentium 4 1.80 such as Intel Pentium 4 1.80 drops 100 MHz at slightly lower power.

A move to Northwood 2.0A doubles cache at lower power on 130 nm. The Socket 478 page lists the Willamette to Northwood path, with Socket 423 as predecessor.