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| The core of the processor contains x86 instructions , these instructions define a processor as IBM compliant or more so as INTEL compliant processor.Th eprocessor consists of floating point unit which contains x87 instructions. The floating point unit as the name suggest is responsible for carrying out floating point operations (real number calculation) which is very important for rendering high quality graphics. The processor has some cache memory which works at full or half processor speed.When processor is handling data from the RAM it drops some of it into the cache memory and the next time it needs some data it first looks for it in the cache memory.If it finds the data in the cache it's called a Cache Hit.A cache hit saves the processor a lot of time as it can access data from the cache memory at full clock speed ,say 400 MHz for a 400 MHz processor whereas RAM works only ar 100 MHz.Anyway cache memory is faster than normal memory as it is SRAM (Static Random Access Memory) which can retain data for a long time unlike conventional memory which is DRAM (Dynamic Random Access Memory) which can retain data for a very short time and needs frequent refreshing.Cache is one of the most important factor in determining the performance of the CPU. For example when celeron was first released it shared the core with the P-II but didn't have any cache.Due to this it's performance was hardly better than the Pentium and this is where it got a bad name. Later when it got the 128 KB full speed L2 cache it almost outperformed the much more expensive P-II which had 512 KB L2 cache running at half processor speed. | |
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| Cache memory is divided into L1 cache present in the core of the processor running at full clock speed and is equally divided as data cache and instruction cache,L2 cache which may be present on the core or kept separately running at full or half clock speed.L2 cache is the one reffered to when you only say 'cache'.Example when you say P-II has 512 KB cache it mean the L2 cache of P-II is 512 KB.Normally the more the cache the better is the performance of the CPU but it has a limit and beyond it increase in size of cache does not have considerable increase in performance. The basic x86 instruction weren't good enough to run highly graphical 3D and multimedia applications so manufacturers started adding custom made instruction sets to their processors. INTEL MMX ,INTEL ISSE and AMD 3D-NOW! are some of the examples. MMX stands for MultiMedia eXtensions which is supposed to speed up integer calculations which help in running multimedia applications.MMX instructions are found in all the INTEL compliant processor manufactured today. ISSE (Internet Streaming SIMD Extension) and 3D-NOW! are capable of performing floating point operations.They can perform upto four floating point operations in one CPU cycle where as x87 can perform only one operation in one CPU cycle. These instructions can also help in improving speed of graphics on the web as they are capable of SIMD (Single Instruction Multiple Data). These instructions give a considerable boost in performance if the software is designed to take advantage of it. |
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