Intel Pentium 4 1.5 socket: Socket 478

What the Pentium 4 1.5 is

The Intel Pentium 4 1.5 is a 1500 MHz single-core desktop processor from August 2001 in Socket 478 form. It runs one NetBurst Willamette core at 1500 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 58 W in a Socket 478 FC-PGA2 package with part numbers SL5TJ and SL5N8 on a 400 MT/s front side bus with a 15x multiplier at 1.75 V.

A 100 MHz lift over the 478 1.4 at a close 58 W envelope makes the 1.5 the steady performance pick of the early 478 Willamette set, which is why it headed launch Socket 478 towers. Intel sold Socket 478 1.5 parts from August 2001 with the 1.4 and 1.6 parts. The chip supports MMX, SSE and SSE2.

Mid Willamette clocks with broad chipset choice suit early Socket 478 towers with SDRAM, DDR or RDRAM paths. The 15x ratio is a clean multiple of the 100 MHz base clock. That is why the 1.5 shipped across all three memory types by board.

Socket and motherboard compatibility

The 1.5 fits Socket 478 early performance desktops with Willamette support. It needs a 478-pin board with a 400 MT/s bus and a BIOS that lists Pentium 4 1.5 Willamette. The Socket vs chipset: what decides whether a CPU works guide covers pairing rules.

Early performance towers are the natural match. Boards listing the Socket 478 1.5 accept the chip with a 58 W cooler. Northwood-only boards with no Willamette voltage strings may refuse it despite sharing the socket.

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. Boards commonly run PC133, DDR200 or PC800 paths for 400 MT/s Willamette 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 58 W.

Upgrade paths

On the same socket, a move to a Northwood 1.6A keeps the board when the support list names 512 KB cache strings. The 1.6A doubles cache to 512 KB at lower 46.8 W on 130 nm, so thermals improve while clocks rise. A Pentium 4 1.4 such as Intel Pentium 4 1.4 drops 100 MHz at slightly lower power.

A move to LGA 775 needs a new board. The Socket 478 page lists the Willamette to Gallatin range for planning.