Factors That Influence Personal Computers Performance

1. The CPU.
   
   High performance, compatibility and upgradability are features that are important. The higher the generation, the better. For example, because of high performance new features, Pentium 75 (fifth generation with the clock rate 75 MHz) will outperform 80486DX100 (which is the fourth generation CPU with the clock rate 100MHz).
   
   Another important feature is word size measured in bits. 80386 and 80486 processors are 32 bit whereas Pentiums are 64 bit processors, thus Pentiums can transfer twice as much data at a time compared to third and fourth generation CPUs.
   
   
2. Clock rate.
   
   Since any step of processing can happen only on the "tick" of the clock (called clock cycle), the faster the rate the quicker the CPU works. The Intel486(TM) processor, for example, is able to execute many of its instructions in one clock cycle, while previous generations of Intel microprocessors require multiple clock cycles to execute a single instruction. The Pentium processors have the ability to execute multiple instructions per clock cycle due to the fact that the Pentium processor's two pipelines can execute two instructions simultaneously. If other modules of the system require more than one clock pulse, the CPU has to wait for them to keep up. This is called a wait state.
   
    
3. RAM.

   It does not make much sense to have a fast processor if you don’t have fast RAM. But note: faster RAM is more expensive.

   The amount of RAM is also important. Today, advanced operating systems require at least 4 megabytes of memory just to boot up a computer. Using more than one application at a time requires at least 8 megabytes, and reasonable performance today calls for 16 megabytes or more. The benefits of adding more RAM include letting you open more applications at the same time, and working with large files or documents. More memory may also make your machine run much faster.

   The quality of DRAM chips used in a memory module is the most important component in determining the overall quality and reliability of RAM. So which chips to consider?

   Enhanced Data Output (EDO) DRAM provides faster data throughput. Systems using EDO DRAM will be faster than similar systems using regular DRAM. EDO DRAM provides even higher performance benefit when used with an L2 cache.

   Enhanced DRAM (EDRAM) can be thought of as RAM that carries its own cache on each module. In an EDRAM-based system, essentially the entire system memory bank is the cache. This can provide dramatic performance improvements. However, at this time, EDRAM is scarce, very expensive and has not been adopted by many system vendors.
   

4. Cache presence and size.
   
   L1 Cache.

   The bigger the on-chip cache size, the better since more instructions and data can be stored on the chip, reducing the number of times the processor has to access slower, off-chip memory areas to get data. For example, Intel has doubled on-chip cache size to 32K on the Intel Pentium processor with MMX technology.

   L2 Cache.

   System memories composed of dynamic RAM (DRAM) alone have not been able to keep up with the dramatic increases in CPU speeds over the years. In order to optimize the memory performance in these systems, designers are implementing architectures using cache memory, resulting in speed increases up to 45%. Expanding secondary cache (e.g. from 128K to 512K) can greatly improve the performance of some applications.

   In a recent industry magazine test of notebook computers, a 486 machine with L2 cache outperformed a Pentium 90 machine without L2 cache by 30%.
   

5. Data bus type and size.
   
   The data bus is the highway that carries information between the processor and the memory subsystem. The wider the data bus, the more information it can transfer. Because of its external 64-bit data bus, the Pentium processor can transfer data to and from memory at rates up to 528 Mbytes/second (five times faster than the transfer rate of the Intel486 (TM) DX2-66MHz microprocessor).

   The PCI local bus greatly improves I/O performance. It can transfer data between the processor and the peripherals at up to 132 MB/second, far faster than the ISA bus rate of 5 MB/second.
   

6. Hard disk capacity and seek time.
   
   High-performance hard drives have at least 1.2 G of capacity, provide an average seek time of 12 milliseconds, a 128 to 256 K hard disk buffer cache with both write-caching and read-caching capabilities, and spin about 4,500 rotations per minute. (You may be familiar with using a disk cache, such as Microsoft SmartDrive, which uses a small RAM buffer to speed up access to a large hard disk.)
   
   
7. Videocard.
   
   A full-featured PCI-compliant VGA card, with at least 1 to 2 MB of video RAM, will further accelerate graphics performance.
   
   
8. CD-ROM drive speed.
   
   At the time of writing of these notes the slowest CD-ROM drive available on the market is quad speed. It may be enough, if you are not running applications from CD-ROM, but only installing them. Otherwise look at octal or ten-speed technologies.
   
   
9. MMX processors.
   
   Multimedia extensions processors (MMX) is designed specifically to support media-rich software and communications applications.. The Pentium processor with MMX technology will give a better, smoother and more realistic multimedia experience. These processors have got 57 powerful new instructions specifically designed to manipulate and process video, audio and graphical data efficiently. However, your system will require software designed for MMX technology (old software must be recompiled to take advantage of new MMX features).

Remember that the key measurement is how your software performs on a given system versus that system's cost, service and warranty, reliability and compatibility.

So first decide what software you will need, look at the minimum hardware requirements for the software to run and then make your decisions about what hardware you will need. To help you make your decisions, following is the list of computer-intensive applications:

Database packages
Computer-aided design/engineering
3-D modeling
Large-scale financial analysis
High-throughput client/server
Network applications
Virtual reality
Rich electronic mail