Hacks #19-29

"How fast can I make it run?" is likely the first question from any PC hacker. In the good old days of the original IBM PC, the answer was a breathtaking 8 MHz, up from 4.77 MHz—but only if you replaced the system's processor, an Intel i8088 CPU, with an NEC V20 chip. (Intel eventually beefed up the i8088 to run at 8 MHz.)

The PC has gone through numerous and tremendous performance improvements, starting with the CPU. At one time, 12 and 16 MHz were the top speeds; then 25 and 33 MHz; then 50 and 66 MHz; then 100, 150, 200, 266, 500 MHz, 1 GHz, and 2 GHz. After 24 years of technological advances, now 3 GHz, nearly 630 times faster than the first PCs, is an everyday, ho-hum, state-of-the-art PC standard.

At every step of CPU performance improvement, the system I/O bus and peripherals have had to catch up. We want the Internet to flash before us, its content challenging the CPU to keep up with the network. There was a time when application programs strained to crunch numbers and print documents; we are now waiting for applications to take advantage of what desktop super-computing capabilities have to offer. Once AMD got the rights to manufacture an Intel i80286 CPU, the horses, cows, pigs, and rocket-fuel powered CPUs were out of the barn, seldom to be corralled again. The functions of the x86 chip were well known and easily replicated: the race was on. The winners are millions of PC users around the globe.

The basic question may be, "Why do I want my CPU, or the entire system, to run faster anyway?" Numerous justifications and solid reasons exist for hacking your system for better performance, including:

• Because applications are slow with the present system

• Because you can get additional performance for little or no expense—a free or cheap upgrade

• Because you can—it's the nature of techies and geeks

The most critical elements in jacking up your CPU speed are also the limiting factors as to how fast it can get: the top speed of the CPU and design of the supporting circuits on the system board. In 1980, the year the PC was born, the IBM PC system board and peripherals could not easily be made to go faster, nor did the components support the challenge. The IBM PC/XT saw some improvement, but the methods of clocking the CPU and the peripherals were so tightly tied together that it took major circuit hacking to speed things up.

Circuit board technology as well as CPU and I/O bus clocking schemes removed many barriers to increased speed, made motherboard makers more likely to support whatever CPU could be plugged into the slot, and made life better for us hackers. If a CPU could be sped up, it gave us more computing power for our dollar. The trick was, has been, and always will be determining which CPUs can or cannot be overclocked (made to run faster than the rated speed).

CPU hacking is not without risk. With speed increases (and occasionally the need to increase the voltage fed to the CPU to accommodate higher speeds), electronic components such as CPUs, chipsets, and memory can get warmer. Some of the downsides to CPU hacking are:

CPU failure

It is possible to push voltage changes too far. Attempts to get the CPU to run faster raise the risk of "smoking" the CPU. Risking an $80-300 CPU for "just one more notch" of performance increase is not good economics.

CPU temperature rise

This can be a fatal condition if not addressed with better heat dissipation and ventilation; you will need to ensure adequate cooling for your CPU.

Higher power-supply current drain

Faster CPUs consume more power, which means a higher capacity power supply is needed.

CPU unreliability

If higher temperatures don't cause a CPU to flake out right away, the design and construction of the CPU itself simply may not be able to keep up with higher speeds or voltages for long periods of time; erratic operation or data loss may results in many cases.

System board, chipset, memory, and peripheral issues

The CPU may run well at higher speeds, but other system components may not operate reliably or at all if the main clock speed is increased; again, erratic operation or data loss may result.

To reduce the risks of CPU hacking, follow these tips: NEVER operate the CPU without a properly attached heat sink—not even for a moment. ALWAYS provide adequate or "overkill" ventilation across the CPU's heat sink. Use a test drive, a drive that does not contain critical data, or back up the drive before overclocking. Expect that you may lose the operating system or datafiles during your testing. If you have an electronic thermometer with a probe, hold the probe tip on the heat sink for 3-5 minutes and check the temperature. Any component that has a surface temperature over 120 degrees is at risk: slow the system down or install additional heat sinks for these devices. BEWARE! It is not uncommon for the surface of an overheated component to exceed 120 degrees—hot enough to burn skin! If the system boots up improperly, operates erratically, or does not keep running for the length of time it takes to run a full set of system benchmark tests (10-30 minutes), you've gone too far in overclocking.

3.1.1 The Great CPU Performance Race

Since the first PC clone, there has been a simple drive to be faster, better, and even cheaper than the competition. This certainly holds true among the PC makers and, at the core of all PCs, the CPU makers.

The CPU speed race did not get exciting until there were three contenders in the race—AMD, Cyrix, and Intel—and the field grew after the relatively short life of the Intel i80386, the world's first 32-bit microprocessor. After those advances, the introduction of the Intel i80486, the promise of a vastly improved Microsoft operating system (Windows 95), and the revelations of the Internet put PC use into the consumer mainstream. The CPU contenders—AMD, Cyrix (now Via), and Intel—battled among themselves, while hackers enjoyed system boards that accommodated any one of these CPU products and provided switches or jumpers to adjust clock speeds to crank them up.

As we explore CPU hacks, we need to know which CPU is in the system now, whether the CPU is hackable, whether the CPU will survive the hack and how, and, of course, what tools (physical or in software) are required to perform the hacks.