Pentium® 4 (Socket 478)

Launch

Socket 478 was introduced in August 2001, less than a year after Socket 423, with an improved pin layout that provided more power pins needed to feed the high speed processors that Intel had planned. In addition to having an additional 55 pins, the Socket 478 packaging was also significantly smaller than its Socket 423 counterpart.

Socket 478 processors (top) compared to Socket 423 (bottom)

Northwood

On launch all available chips were based off the existing Willamette core at speeds up to 2GHz in the new package, the die itself remained unchanged.
In January 2002 however the 130nm Northwood core was unleashed. Initially at speeds of 1.6, 1.8, 2.0 and 2.2GHz (the 1.6, 1.8 and 2.0 suffixed with 'A' to differentiate them from the equivalent Willamette's) the Northwood saw a doubling of its L2 cache to 512KiB which brought big improvements in performance while the TDP was reduced around about 33% compared to the equivalently clocked Willamette.

A 2.4GHz part followed in April and then the Northwood 'B' was introduced in May bringing an effective 533MHz front side bus at speeds of 2.26GHz, 2.4GHz, and 2.53GHz (It gained the name Northwood B as a B was used to differentiate the two 2.4GHz SKU's).
August saw the introduction of another 4 parts, the 2.5 and 2.6 (400MHz FSB), and 2.66 and 2.8GHz (533FSB). Then on November 14th 2002, Intel broke the 3GHz barrier with the introduction of the Pentium 4 HT 3.06GHz. While still on the 533MHz FSB this part added a feature not seen in previous desktop processors, Hyper-threading. Hyper-threading already existed on the Xeon and is explained on that page.

The 3.0GHz, 800MHz (4 x 200MHz) front side bus part was launched in April 2003, with 2.4, 2.6, and 2.8GHz SKU's following on the 21st of May.
All 800MHz FSB Northwood's (Known as the Northwood 'C' as 'C' was used to differentiate them from the other Pentium 4's at the same speed, getting confused yet?) featured hyper-threading technology and could well be considered Netburst's finest hour, with the 2.4 part offering incredible value for the enthusiast who was willing to start cranking up the speed.
Later a 3.2GHz part was introduced, and then a 3.4GHz one on February 1st 2004, a bizarre choice as this was the same day Prescott launched....

There were 3 mobile derivatives of Northwood, the 35W Pentium 4-M at speeds of 1.4 to 2.6GHz on a 400MHz FSB (this can be identified by its lack of heatspreader), and a pair of 76W parts, the Mobile Pentium 4 which ran at 2.4GHz to 3.2GHz and the Mobile Pentium 4 HT which covered 2.67 to 3.2GHz and featured hyper-threading. Both these parts used a 533MHz FSB.

Prescott

Introduced on February 1st 2004 the Prescott was perhaps the most disappointing launch of Intel's history.
The Netburst architecture had been substantially overhauled, with the pipeline length increased to 31 stages, from 20 for the original Willamette and Northwood cores, SSE3 was introduced, and the L2 cache was doubled to 1MiB.

Despite debuting Intel's 90nm process technology power usage and therefore heat output was greater than an equivalent speed Northwood.
Combine this with the longer pipeline, which even with improved branch predictors and the larger cache resulted in a clock for clock performance drop, and you had a severely disappointing product.
It couldn't even get away with being clocked higher as the Prescott launched at a maximum clock frequency of 3.4GHz and the Northwood 'C' received a speed bump to 3.4GHz on the very same day which almost felt like an apology....

The initially launched Prescott's were suffixed with an 'E', and wouldn't work in most motherboards without a BIOS update (or at all in some boards).
Later a 533FSB part without hyper-threading was introduced and got an 'A' suffix.

My head hurts....

Some to just give an idea of how confusing things got by the end of Socket 478's life you had the following Pentium 4's.....

1.4, 1.5, 1.6, 1.6A, 1.7, 1.8, 1.8A, 1.9, 2.0, 2.0A, 2.2, 2.26, 2.26A (now 'A' standing for the Prescott core, not the Northwood of the lower speed 'A'), 2.4, 2.4A, 2.4B, 2.4C, 2.5, 2.53, 2.6, 2.6C, 2.66, 2.66A, 2.8, 2.8A, 2.8C, 2.8E, 3.0, 3.06, 3.0E, 3.2, 3.2E, 3.4, 3.4E.

And that's without mentioning the four different mobile cores and Pentium 4 Extreme Editi... oh no I've gone cross-eyed.

Archived Pentium® 4-M 1.6GHz

Laptop pull, assumed working. Received from a friend.

Archived Pentium® 4 3.0GHz

Old system pull, assumed working.