Monday, October 26, 2009

All you ever want to know about PCs: CPUs


Well let’s start with the basics, CPU are the brains of the PC while the Motherboard is the skeleton and nervous system. The make things fun desktop CPUs are either with pins or none. Those that still come with pins are the current AMD ones while Intel have implemented a pin-less route using circular connectors on the bottom of the CPU while the socket it plugs into has the pins. These pins are bent to provide some spring tension.

Naturally, the AMD CPUs are prone to pin damage from bad handling or just bad luck. But not to fear unless the pins break completely off you can very gently bend them back using a credit card. Make sure to use the other pins alignment as a guide. Intel CPUs do not suffer this hazard but should you damage the pins in the socket expect a much harder time getting them back into working condition.

Thankfully installing CPUs are a pain free task. Just align the marked of the CPU with the marked edge of the socket and drop it in. If done correctly there will be no resistance to the CPU going into socket. If there is resistance check your alignments again and see if there is anything in between the CPU and the socket.

Other that bent pins CPUs are pretty tough compared to the earlier generations. This is thanks to the hard caps all CPUs wear lovingly known as a heat spreader. The heat spreader does not only help spread the thermal waste from the small silicon die but also help spreads the weight placed on the CPU by the heatsink.


All CPUs nowadays have thermal protection should things get too hot. Motherboards will take preventive measures when CPUs reaching danger temperatures either by completely shutting down the PC or by throttling the speed of CPU down until the temperatures reach safe levels.

Another method of killing of a CPU is throwing tons of electrical power into it in hopes that it can clock at a higher speed. This overvolting will cause fatigue (electromigration) to the CPUs circuits which eventually will give. The life expectancy of any CPU really depends on the said CPU like overclocking gems a few will stand the pressure and give you years of service. Others will sometimes croak in less than a year. This also depends on how much you can cool it. The hotter the CPU is the more electromigration you incur.


Before we talk multi-core CPUs let quickly talk about Hyperthreading. Hyperthreading does not mean you have a free CPU core for each CPU core you bought. What Hyperthreading is, is that with the right OS your Intel CPU can use the unused instructions and idle clock cycles of your CPU core ran another set of calculations and instructions. This is done only if you have the free CPU resource for it. If a program is already occupying 80% of your CPU resource most likely the OS will not run any other instructions in parallel. AMD does not have Hyperthreading in their CPUs because they have designed their CPUs to run single operations more quickly compared to Intel’s CPUs. This has been the reason why Hyperthreading had disappeared from the Core Duo CPUs onwards. Hyperthreading was not as efficient as just having the CPU run one operation quickly since two operations on one CPU core sometimes trashed the Cache on it. Intel has now brought back Hyperthreading with their Core i7 lines and some of the CPUs in their Core i5 and Atom lines.


Last time when someone mentions ‘your CPU’ they meant the processor core on your silicon die. Nowadays, it is the other way round; the CPU now refers to the silicon die which can house anywhere from one core to six cores. These cores are the brains of the CPU where as the silicon die is the head. You may come across some CPU packages where there are two dies each with a single core on them that are connected to each other sharing the Cache such as the Pentium D.

Unfortunately, like Hyperthreading having multiple cores does not make your OS and the programs on it run twice as fast. All consumer grade OSes excluding Linux take very little advantage of a multi-core CPU. This has left programmers no choice but to optimise their own programs to take advantage of more than one core. Hence, you will notice not all programs will run four times faster just because you have a quad core CPU. A good example of this is games; only a few games currently take advantage of a multi-core CPU. One of them is Supreme Commander while the others will only benefit if you spend your money on a better graphic card, more RAM and RAID 0 your hard drives.