Factors affecting performance

In the early 90’s the principle trend in increasing performance was the increase in clock speeds. However that led to a bottleneck where other peripherals were slowing the core of the machine down and becoming the bottleneck.

In April 1965 the co-founder of Intel® - Gordon Moore made a prediction that the amount of transistors that would be included in a processor would double every 18 months. So far this has remained true. And has become known as ‘Moores Law’. Further information can be found here.

The table below is a summary of the amount of transistors, manufacturing technology and Clock speeds in Intel® chips from 1971-2012 .

A visual timeline of Intel Processors can be seen below (best viewed in a separate window) 

Source (download.intel.com/pressroom/kits/IntelProcessorHistory.pdf)

The average home PC now has a processor with multiple cores (between 2-8). This is effectively two (or more) processor dies integrated into one processor. This allows multiple tasks to be executed at the same time.

This was as a result of the trend in the late 90’s for faster single core processors. The major issue with this strategy was that this increased the amount of heat that was being produced. So modern CPU’s usually consist of multiple smaller cores.

If applications are optimised for this multi-threaded approach it can increase performance considerably. Some processor cores can even have multiple program threads running at any one time, giving the operating system. The top supercomputer in the world at present (April 21) has 7,630,848 cores (link).

Double the cores does not mean double the performance

There are various issues around multiple cores that prevent a doubling of cores meaning a doubling of performance. Some are:

• Potentially needing to share cache memory

• Resource Starvation - One of the cores may need data in use by another core

• Software has to be designed with multiple core access in mind

• Access to RAM

If the data bus width is increased then the amount of data that can be moved in a single operation, so less fetch operations are required.

This has already been covered, an increase in clock speed allows the processor to execute more instructions per second. This has partly been possible due to the speed of modern transistors and the increase in the amount of transistors on a single processor.

However there is a physical limit to the amount of transistors that can be placed on a chip and there are heat considerations. Another method of increasing performance is over-clocking, this is when a processor or other component is made to run faster than it was originally intended. This can cause issues such as instability, over voltage and overheating problems.

As processing power has increased the tendency for user’s to have more applications open has led to an increase in the demands on system RAM. So there has been a tendency to increase the amount of RAM available to a system, with average machines shipping with 8-32 GB plus of RAM compared to approximately 16-128MB RAM in 1998.

However you have to be cautious when upgrading RAM as it will only increase systems performance in particular situations, basically whenever the amount of RAM needed is more than is available and is causing the machine to use virtual memory (a temporary section of backing storage). If there is RAM unallocated then it is more than likely that adding additional RAM will make no difference in performance.

As multimedia entertainment and games have risen in popularity the use of dedicated graphics cards that have on-board graphics memory and specialised Graphics Processing Units (GPU's) have increased. It is possible to buy graphics cards with up to 11GB of memory (March 19). This memory will purely by used by the graphics card for the processing and generation of graphics. This is much faster than having to access main RAM.

More powerful graphics cards usually have faster/more GDDR (Graphics DDR) and more powerful GPU's ( Graphical Processing Units) which are essentially specialised processor for rendering graphics.

In parallel with the increase in the amount of memory the amount of backing storage has also increased. At the time of writing (Apr 21) the largest capacity internal Hard Disk Drive for a domestic PC is at 18TB. This has been helped by the advent of technologies such as perpendicular recording. This is also allowing programs to install more information on the host computer.