History of Overclocking Part Two

Athlon, Duron
(1999-2005, 0.25µm-0.13µm process, 500-2330MHz)

AMD’s seventh generation CPU finally got a strong FPU and was incredibly fast. Starting as a Slot A processor similar to Intel’s Slot 1, it was the result of AMD hiring DEC engineers and consequently gaining the benefits of the high performance Alpha architecture, notably the EV6 bus.

The biggest benefit of the EV6 was it was Double Data Rate (DDR), meaning that while the clock only had to beat 100 times a second, it was interpreted as 200MHz.

The Slot A Athlons were the first from AMD to be multiplier locked, due to the same dodgy resellers that plagued Intel.

The Internet arguably hit its biggest boom and enthusiasts worldwide traded ideas through hardware websites. The Athlon became the choice of the enthusiast. Insane hardware modding began and unsoldering and resoldering specific resistors to the Athlon resulted in the multiplier being unlocked. This would eventually transform into an off-the-shelf solution called ‘Goldfinger’, which attached without solder to the gold circuit connector at the top right of the Athlon, offering either dipswitches or dials to set the multiplier – unfortunately these solutions didn’t offer access to the L2 cache divider like the earlier homebrew attempts.

AMD shifted to a socketed solution (Socket 462, or Socket A) for its second revision chips, codenamed ‘Thunderbird’. It was here that AMD won the speed battle, releasing the first GHz processor and taking serious market share from Intel due to significantly better performance per clock. Socket A would continue to be used until the Athlon 64, something that appealed to upgraders over Intel’s constant socket-switching shenanigans.

Socketed Athlons were multiplier locked by laser etching the CPU itself, with traces being removed from the surface between four sets of contact points, known as the L1 bridges. Amusingly, people reconnected these with a mere pencil, unlocking them once again.

Later locks would involve a trench being burnt into the CPU to mitigate this – so people simply filled the trench with a non-conductive material and whipped out the old 2B once more.

AXIA-revision Athlons became as famous as the Celeron 300A for overclocking headroom. The AMD age had arrived.

AMD’s Athlon could be multiplier unlocked by a mere pencil. The AXIA Athlon was a famed overclocker.

The Duron was released to compete with the Celeron, the fantastic price versus performance making it the gamer’s choice. Its only distinction from the Athlon was having a quarter of the L2 cache at 64KB, and was limited to 100MHz bus speeds initially when the Athlon hit 133MHz.

The Athlon XP came in late 2001. It was SSE compatible, and on average 10% more efficient than the Thunderbird at the same clock, and re-introduced AMD’s PR rating. People began to understand that MHz wasn’t everything and instructions per clock were more important. AGP 8x became common.

Unlike the Pentium 4, the socketed Athlon’s core was exposed, with no heat spreader to protect it from a heavily ratcheted-down heatsink – as a consequence, many cores were crushed to death.

VIA became a force in with its KT133A and KT266A chipsets for AMD, although numerous compatibility problems arose, particularly due to PCI bus latency. Several homebrew tools popped up to fix the issues. The latter chipset brought DDR RAM into the fray, thanks to VIA’s excellent memory controller. Before this point, DDR was only marginally faster than SDRAM and a whole lot more expensive.

NVIDIA entered the market with the nForce, but it wouldn’t be until the nForce2 that people would take it seriously, thanks to the dual channel RAM support, SoundStorm onboard audio, dropping of the integrated GPU and the stability of the platform compared to the VIA alternative. NVIDIA rapidly expanded to be one of the biggest players in the market, arguably popularising the integrated approach on the motherboard. Motherboards appeared that ignored AMD’s multiplier lock.

RAM ratios became more prominent, allowing greater control over how they were divided from the FSB, particularly in boards offered by DFI.

The Athlons famously ran hot, requiring even louder coolers, but they’d be nothing compared to Intel’s alternative...

Pentium 4
(2000-2006, 0.18µm-65nm process, 1300-3800MHz)

Bear with us here – the Pentium 4 changed so much over its tenure that there’s barely enough room for history, let alone overclocking.

The first Pentium 4 was by all accounts a flop. It was the first architecture redesign since the Pentium Pro and introduced a deep pipeline called NetBurst in the hope that massively ramping clock speeds would overcome the latency. Pentium IIIs at the same clock speeds would outpace it.

While speeds climbed fast initially, soon the 3GHz barrier was hit, and things progressed slowly up to a final 3.8GHz – far short of the 10GHz predictions. The Pentium 4 was notoriously hot throughout its lifetime, requiring exotic cooling solutions. SSE2 was introduced, but short of video encoding didn’t seem to offer huge benefits.

Motherboards required a 20-pin power connector like the Athlon alternative, but also needed a 4-pin EPS12V connector and a 6-pin auxiliary connector – it was one power hungry beast. In fact so many new parts were required compared to AMD’s platform (PSU, RAM, in some situations a case, as early HSFs were recommended to be bolted to the chassis itself) that it turned people away. The problem compounded when it launched on Socket 423, but quickly transitioned to Socket 478, burning early adopters.

AMD’s platform may have been double-pumped, but Intel’s was quad – resulting in an initial effective FSB of 400MHz compared to 266MHz. Thermal throttling was introduced, the processor slowing itself down if it got too hot. Overclockers instantly turned it off.

2002 saw the introduction of the 130nm, 533MHz FSB Northwood revision, which put Intel back in the race against AMD’s Athlon XP, although it required higher clock speeds. The Northwood 1.6A was released in June 2002, which reached a thumping 2.57GHz when we overclocked it.

RDRAM was finally dumped and SDRAM was enabled on the 845 platform in 2002, with DDR following in 2003. By this stage DDR prices had crashed, the significant price reduction invigorating the Pentium 4 market. It was VIA however that was first with a Pentium 4 DDR board with the Apollo P4X266, despite Intel’s complaints that it was not licensed to make chipsets for its processor.

HyperThreading was introduced with the 3.06GHz model in November 2002, allowing one core to process two threads at once – this was done by allocating idle execution units extra work. In theory this was meant to speed things up, but in a number of situations actually slowed the processor down, and many gamers simply turned it off.

Northwood finished at 3.4GHz in early 2004, on an 800MHz bus, but the overclockers did better. The C1 revision in particular gave 3.5GHz from 2.2GHz, and there were reports of 4GHz from the 3.06GHz models.

The Pentium 4 Extreme Edition hit the market with an unlocked multiplier, opened for the first time since the Pentium II. An L3 cache of 2MB was added for an extra speed boost, and it ran on a 1066MHz bus.

The Prescott revision came in 2004, and despite being shrunk to 90nm would run hotter than ever before, with the Northwoods outperforming it clock for clock in most games – only SSE3 and extra cache saved it in applications. AMD would take the lead once more with its Athlon 64.

It was at this point that Intel shifted to Socket 775, DDR2, PCI Express and upped the bus to 800MHz. DDR2 was a long term investment, being slower than DDR at the time. A strategy began similar to what AMD implemented with Socket A – we would still have Socket 775 three years later. PCI Express finally rid us of the PCI and AGP buses, running at an asynchronous 100MHz.

The idea of PR ratings was borrowed from AMD, although it seemed more to hide the fact that high GHz didn’t equate to high performance. The 4GHz mark was never officially reached, Intel going down the dual core route instead. Prescott was eventually revised to include 64-bit instructions (sporting AMD 64
compatible code called EMT64, another concession) and virtualisation technology.

The 65nm Cedarmill was the final incarnation of the Pentium 4. It reached 3.6GHz and was most notable for hitting the highest frequency ever – 8GHz – a world record overclock yet to be beaten. LN2 was used, along with motherboard voltage mods to achieve the massive speed.

LGA775 is Intel’s longest serving socket.