The Processor

Generally, overclocking suits processors from Intel — for example, Pentium, Pentium MMX, Pentium II, Pentium III, and Celeron processors — although other companies' processors also often take to the procedure as well. There are no processors that can be characterized as “overclockable” or “non-overclockable”. Everything depends on the specific configuration of the computer, the processor type, series, and even the particular instance.

Based on the experience of overclocking processors of the same type but intended for different clock frequencies, the following trend becomes obvious. The best overclocking results can be achieved with the first processors released after significant changes in technology, core architecture, etc. This is reasonably explained by the fact that the first releases of the new generation of processors evidently have a large technological reserve. Of course, the first batches of processors contain a lower percentage of consistently stable chips released. This, though, is the problem of the manufacturer. Those processors that have been tested and released, however, allow you to significantly increase the clock frequency. Subsequent releases of processors are more difficult to overclock. This situation has occurred in Pentium, Pentium MMX, Pentium II, and Celeron processors. For example, Pentium processors with the clock frequencies of 75–100 MHz and Pentium MMX 166 overclocked very well. Certain Pentium 75 processors allowed you to increase the clock frequency to 112 MHz, while Pentium MMX could be overclocked to 208 MHz. Within the Pentium II processor family, the following processors were overclocking leaders: Celeron 266 and Celeron 300 (the first of the Celeron processors), Celeron 300A and Celeron 333 (the first of the family of processors with the new Mendocino core and with a built in L2 cache memory that works at the frequency of the processor). When overclocking these processors, it was possible to increase the clock frequency by more than 50% with, of course, a corresponding rise in performance. The subsequent, more powerful processors, with clock frequencies already increased by the manufacturer, show weaker results in an overclocked mode. However, there is a basis to claim that the forthcoming first members of the Celeron processor family, intended for a host bus frequency of 100 MHz and created by new technology and with new cores, will live up to the expectations of overclocking enthusiasts.

It's worth mentioning that Pentium II and Pentium III processors are significantly different from their predecessors. This difference lies not only in the more complex internal architecture, but also in the construction of the processor, which now uses a SEC cartridge connected through Slot 1. An important feature of processors of this type is the fact that, besides the processor chip, this cartridge contains a controlling chip and a level two cache memory (L2) intended for work at half of the frequency of the processor core. Unfortunately, in many cases the chip used in the processor is not noted for its high-speed abilities. This greatly reduces the possibilities of overclocking. Sometimes, however, a series of processors can be found that do have high-speed chip. These processors are the preferred ones for overclocking. Incidentally, Celeron processors with clock frequencies of 266–300 MHz do not have the L2 cache memory with its relatively slow chip, and this is exactly the reason that these processors with Slot 1 can reach such a high level when overclocked. The next generation of Celeron processors, Celeron 300A, Celeron 333, etc. were released with a high speed L2 cache memory inside the processor chip, able to work at the frequency of the processor core. The code name of this core is Mendocino. Processors of this type possess a high performance level and make a good showing as a processor that takes well to overclocking. Both processors in SEC cartridges with Slot 1 and processors in PPGA cases with Socket 370 have been released.

The existence of a huge quantity of falsely labeled (re-marked) processor instances complicates choosing the best processor. You must try to avoid remarked processors. A “re-marked” or “sawed-off” processor is one whose original label has been filed off and replaced with a new one. Remarking is illegal, and done in clandestine laboratories in some countries. A falsely labeled processor allows it to pass for a more powerful one than it actually is, and therefore will be sold at a higher price. This is what happened to, for example, the AMD 486DX2-66, series 25253, which was “transformed” into a 486DX4-100. Because of this, in 1995 AMD had to stop the release of the DX2/DX4 series with a changeable multiplier. Later on, fake labels were being made for Intel processors too: Pentium, Pentium MMX, Pentium II, and Celeron.

Telling a real processor from a re-marked one is not as easy as it may seem at first glance. You should take into consideration the fact that false marking is relatively competently done, with the use of modern technical instruments and technology, including lasers. This is why there is no unambiguous way to tell if a processor has been re-marked. There are a few indirect ways by which you can judge the probability of a processor having been falsely marked. For example:

• The processor becomes unstable at the clock frequency immediately following the rated one. However, keep in mind that this may happen with genuine processors as well.

• The processor only works while cold. When the temperature of the case reaches the region of 70–80°C^[*], you begin to get errors; but again, this may also be the case with real processors, that is, ones that haven't been re-marked.

• The symbols of the label are not engraved, but are drawn on or raised, or the depth of the engraving is very shallow. This does not apply to Texas Instruments processors, which are not engraved at all.

• The symbols of the label, after a careful, strongly magnified examination, look as if they were smeared, or carelessly done, etc.

• The frequency mark on the lower side of the case (if there is one) does not coincide with the frequency written on the upper side.

• Identification data given by such programs as SysInfo, CPUID, and similar programs do not match the data for the type or series of processor that you are supposedly using.

In order to minimize the possibility of buying a re-marked processor, you are advised to buy one from an authorized dealer or distributor.

You should note that certain firms that deal in the assembly and sale of computers overclock their processors with the aim of increasing their profit. Of course, they don't inform the customer of this fact. Thus, they are simply cheating you, which, by the way, is prosecutable by law. Usually, these are smaller firms that usually don't stay in business for very long.

Incidentally, the BIOS of modern motherboards is generally able to define the clock frequency of Pentium II processors. To do this, you need simply go into BIOS Setup to the appropriate parameters. Checking this may serve as a test of the computer for its overclocking possibilities, and will also help to defend you from unprincipled salesmen. However, this test will not always help in identifying re-marked processors, as their architecture and construction has undergone certain changes.

You should pay attention to the fact that re-marked processors seem as if they were intended for work in an overclocked mode. Indeed, the mode set to match the false marking on the case of the processor will correspond to one of the overclocked modes. From here you can see that it will be difficult to further overclock the processor. Although, if you increase the CPU voltage, you may be able to make even a re-marked one work a little faster and perform a little better.