Intel Pentium 4 1.8 socket: Socket 423

What the Pentium 4 1.8 is

The Intel Pentium 4 1.8 is an 1800 MHz single-core desktop processor from July 2001 in Socket 423 form. It runs one NetBurst Willamette core at 1800 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 67 W in a Socket 423 organic PGA package on a 400 MT/s front side bus with an 18x multiplier.

The plain 1.8 spelling marks the Socket 423 package while 1.80 marks Socket 478 and 1.8A marks a separate Willamette bridge string, which is why board lists carry three 1.8 GHz entries with different sockets. Intel sold the Socket 423 1.8 in July 2001 near the end of the 423 run. The chip supports MMX, SSE and SSE2.

Late 423 clocks with RDRAM bandwidth suit final Socket 423 towers with AGP graphics. The 67 W envelope needs the tall 423 cooler. That is why the 1.8 shipped in late Rambus performance systems.

Socket and motherboard compatibility

The 1.8 fits Socket 423 late desktops with Willamette support. It needs a 423-pin board with a 400 MT/s bus and a BIOS that lists Pentium 4 1.8. The Socket vs chipset: what decides whether a CPU works guide covers pairing rules.

Late RDRAM towers are the natural match. Boards listing the Socket 423 1.8 accept the chip with a 67 W 423 cooler. Socket 478 boards take the 1.80 spelling only.

Memory, PCIe and cooling

Memory is RDRAM and SDRAM through the board chipset, matched to the board slots. The CPU has no memory controller. Late i850 boards commonly run PC800 RDRAM pairs for 1800 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 423 bracket with a cooler rated for 67 W.

Upgrade paths

On the same socket, a move to a Pentium 4 2.0 Socket 423 keeps the board when the support list names it. The 2.0 adds 200 MHz at higher power with the same bus. A Pentium 4 1.80 such as Intel Pentium 4 1.80 is the Socket 478 counterpart at the same clocks on a new board.

A move to Socket 478 Willamette needs a new 478-pin board with its own bracket. The Socket 423 page lists the short 423 range with Socket 478 as successor.