Pushing the boundaries of silicon while microprocessors exist
Enthusiasts have been pushing the limits of silicon’s capabilities since microprocessors have existed. Early overclocking attempts included soldering and replacing quartz oscillators, but this practice quickly turned into changing the system bus speed using DIP switches and jumpers on the motherboard.
Internal clock frequency multipliers were introduced, but they were soon blocked as unscrupulous vendors removed the official frequency ratings and applied their own faster markings. System buses and dividers became key for the majority, while ultra-enthusiasts physically changed the electrical characteristics with the help of hard modding.
The current landscape dates back to the appearance of internal clock multipliers. The system bus speeds began to be regulated more and more to maintain the stability of the system, which once again equalized the rules of the game for the competitive nature of overclocking.
These are just some of the iconic processors revered for their overclocking prowess. Read more!
Note: This feature was originally published in December 2014. We continue to improve it every two years, because CPU overclocking is as cool today as it has been since i286. Part of our annual #ThrowbackThursday initiative.
Intel Pentium MMX 166
Release date: January 8, 1997
Stock clock frequency: 166 MHz
Overclocking: 207-266 MHz (~54%)
The Pentium MMX appeared in the midst of shady sellers, and x86 processor vendors reacted by blocking the upper limits for multipliers. Thus, many MMX relied on increasing the bus frequency for overclocking. Unlocked MMX processors offered more opportunities for overclockers, and the unlocked MXX 233 was in the lead, although its price of $594 was prohibitively high for many.
At a price of $407, the MMX 166 was more profitable, and in combination with a reliable 430TX-based motherboard with a 75 MHz bus frequency, 225 or 266 MHz (3 or 3.5 multi) were within reach. To crack 200 MHz, the MMX 166 with a locked multiplier would need to use an 83 MHz jumper setup if available (2.5*83 for 207 MHz), although stability and heating at this bus speed were much more problematic, as was the quality source. EDO/SDRAM RAM is required to operate at this frequency.
Release date: March 1992
Standard clock frequency: 40 MHz and 50 MHz
Overclocking: 66 MHz (~65%)
The P24 DX2 486 processors introduced a CPU clock frequency multiplier, doubling the system bus speed, and the system bus frequency itself was adjusted using jumpers on the motherboard or DIP switches. Initially including 20, 25 and 33 MHz variants (later supplemented with 40 and 50 MHz models), users had a path to overclocking that did not require soldering and replacing the clock crystal oscillator.
In addition, you can get the DX2-66 performance for $799 by buying a more modest 486DX2-40 for $400 and increasing the default bus frequency from 20 MHz to 33 MHz.
Problems with stability and the VLB slot at a bus frequency above 33 MHz meant that the overclocking margin decreased as the base frequency increased — to such an extent that many Intel DX2-66 processors did not overclock at all, and the few that overclocked were often limited to 80 MHz (2 x 40 MHz).
Intel Celeron 300A
Release date: August 24, 1998
Stock clock frequency: 300 MHz
Overclocking: 375-504 MHz (~55%)
Think legendary. The Celeron 300A largely contributed to the revival of mass processor overclocking in the late 90s due to the ease with which it could be done. Overclocking by 50% to 450 MHz was as simple as changing the bus frequency from the nominal 66 MHz to 100 MHz. Although some boards reached a maximum frequency of 83.3 MHz, limiting the OC to 375 MHz, motherboards supporting the FSB frequency of 103 MHz could give 464 MHz.
A more advanced chip with a voltage surge could operate at a frequency of 112 MHz FSB to output 504 MHz. It is noteworthy that 300A can usually reach 450 MHz without any additional voltage requirements beyond the nominal 2.0 volts. The chip’s performance was also facilitated by the presence of L2 cache memory on a chip, and at a price of $149, it was especially accessible to system builders.
AMD Athlon 700 (Thunderbird) / Duron 600 (Spitfire)
Release date: July 5, 2000 (Athlon 700) / June 19, 2000 (Duron 600)
Standard clock frequency: 700 MHz / 600 MHz
Overclocking: 770-900 MHz (~12%) / 800-1000 MHz (~59%)
The AMD Thunderbird pencil mod was an overclockers’ dream. AMD has blocked the voltage and multipliers of its K7 line to prevent fraudulent re-labeling of processors towards higher specifications. Overclockers quickly realized that bridges embedded in a silicon enclosure are the key to maximum performance.
Initially, the combination of connecting bridges in blocks L3, L4 and L6 gave way to the connection of connections L1 to unlock the multiplier. It was also possible to connect L7 connections to change the core voltage, and this process could be as simple as using a soft graphite pencil or a conductive silver pen.
Since the AMD EV6 system bus is sensitive to overclocking, the multiplier overclocking yielded results, and Duron was in the lead due to a lower core base voltage (1.5 V vs. 1.7/1.75 V), which increased the relative overhead to the maximum allowable 1.85 V.
For $112 and a little time, the Duron 600 easily approached the performance of a processor many times higher than its price.
Intel Core 2 Quad Q6600 G0, revision
Release date: January 8, 2007 (revision B0) / July 22, 2007 (revision G0)
Standard clock frequency: 2.4 GHz
Overclocking: 3.4–3.6GHz (~46%)
The Core 2 Quad Q6600 has achieved an enviable record of durability and performance, becoming the de facto choice for overclockers who need a budget quad-core processor. As soon as the processor dropped in price from the original $851 in January 2007, it quickly fell to $530 in May, and a further price change in July coincided with the appearance of the G0 version. The 2.4GHz quad-core chip cost $266 and cost the same as the new 3 GHz dual-core E6850 processor, a frequency that the earlier version of the B3 Q6600 could comfortably eclipse.
The new G0 stepping offered slightly lower power consumption, which led to the same improvement in overclocking capabilities, as a result of which many users could quite easily support frequencies from 3.4 to 3.6 GHz. The introduction of an affordable Intel P35 platform and a further reduction in the price of the Q6600 in 2008 to US$ 224 (April) and to US$ 183 (October) provided an opportunity for reliable overclocking in the 50% range (9-fold multiplier x 400 MHz FSB for 3.6 GHz) on a moderate budget, which remained very competitive yet long after many of his contemporaries disappeared.