Custom PC - UK (2021-05)

130nm Northwood core, along with a new dinky package

called Socket 478. The top-end Northwood Pentium 4 HT

CPUs also brought us an idea that we still use today, which

is executing more than one thread simultaneously on one

core, with the HT standing for Hyper-Threading.

The way Hyper-Threading works has changed a bit

since then, but the principle is the same – Windows saw

a Pentium 4 HT CPU as two processors, with the CPU

splitting its one core’s resources to create a virtual second

core. Hardly any desktop software was properly multi-

threaded at this point, but it worked well in software

optimised for dual-CPU setups, such as Lightwave.

Next came Gallatin, which introduced the Pentium

4 Extreme Edition with Hyper-Threading and a

3.2GHz clock speed for enthusiasts. Until this time,

Pentium 4 CPUs had maintained the 20-stage

pipeline, but then came Prescott with its 31 stages,

fabricated on a 90nm process, and clock speeds

of up to 3.8GHz. By this time, the thermal and

power demands of Pentium 4 were looking

utterly ridiculous.

NETBURST, AHEM, BURSTS

By the time Prescott was launched, the power and thermal

demands of NetBurst had already made it redundant in the

laptop world. Intel had introduced the Pentium 4-M, but

its thermal demands had resulted in thicker laptops and

slow performance. Not surprisingly, the first part of Intel to

backtrack on NetBurst was its mobile division in 2003, with

the introduction of the Pentium-M.

It was fabricated on a 130nm process, and took some of

the good ideas from Pentium 4, such as the front side bus

and improved branch prediction, but attached them to a core

based on the P6 core from the Pentium Pro days, with a

much shorter pipeline and a massive load of cache.

The result was a really good mobile CPU, with great

performance and decent battery life. People started saying

that Intel needed to do the same on the desktop, but Intel

had sunk so much investment into NetBurst on the desktop

at this point, and it doggedly stuck by NetBurst 4 for a few

more years, bringing it into the dual-core era and dropping

the ‘4’ from the end of the Pentium brand.

It wasn’t until 2006 that Intel finally threw in the towel on

NetBurst. There were rumours flying around the Internet on

the day before it happened. I phoned Intel’s UK PR rep the

next morning and asked him if there was any truth in them,

and he laughed at the very idea of it. A few hours later he

called me back, sheepishly confirming that Intel was indeed

about to completely overhaul its desktop strategy.

NetBurst was in the bin, and so was the Pentium brand as

a sign of premium quality. Intel’s next desktop CPUs would

feature the Core 2 brand, and would again be based on the

P6 core Intel had abandoned years earlier. We’d learned that

there was more to CPUs than clock frequency, and that you

don’t necessarily have to reinvent the wheel to get ahead

in tech.

Then, the later 865 and 875 chipsets went on to support

200MHz (400MHz effective) DDR memory in dual-

channel mode, which went well with Intel’s latest Pentium

4C chips, which had an 800MHz FSB. RIP RDRAM.

THE 64BIT QUESTION

Intel had dropped the ball with the Pentium 4, and it

had taken several years to get to the point where it had

affordable memory and decent performance. That would

be fine if AMD had been resting on its laurels, but in late

2003 AMD unleashed its AMD64 architecture, resulting in

its famous Athlon 64 desktop CPUs.

The headline was 64-bit computing. However, it’s worth

remembering that, at this time, there was no 64-bit version

of Windows XP, and that it would take a good few years

before 64-bit Windows became a standard. AMD had also

removed the front side bus from its CPU design, introducing

an integrated, on-die memory controller, which reduced

latency. The first Socket 754 Athlon 64 CPUs only supported

single-channel memory, but the Socket 939 CPUs in 2004

supported dual-channel memory.

While the integrated memory controller and 64-bit

instructions are often touted as the benefits of the Athlon

64 over NetBurst, the main difference when it came to

performance was that AMD64 had a much shorter pipeline,

with just 12 stages. Intel would later add support for 64-bit

instructions to some of its Pentium 4 CPUs, but

AMD64 CPUs were just massively more efficient in terms of

instructions per clock, thermals and power consumption.

LATER REVISIONS

There were several iterations of Pentium 4 over the years,

starting with a die shrink from the 180nm Willamette to the

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