Connectivity
High Performance external disk drives or disk arrays connected using PCI SCSI cards offers substantial increase in data transfer rate compared to connecting them with systems on board SCSI ports. The difference of performance advantage is 70 MB/s (theoretically)
Processor
The CPU is where all information is processed, the clock speed, size of the cache buffer and speed of the cache of the CPU is critical for data processing at high speed. New faster CPU upgrades are available as the technology moves on. CPU upgrades provides another inexpensive solution to add performance to the computer , considering the cost of a new computer.
Internal or external SCSI ports available on a Macintosh have a Xfer rate limitation of 5-10 MB/sec. These ports may be used for connecting backup or storage SCSI devices but are not meant to feed data to the CPU for higher speed. For example, Zip, Jaz or scratch SCSI disk drives.
Memory
The main memory in the system acts like a cache buffer between the system's CPU and disk drive. System performance depends on two important factors.
1) How fast the data is brought from the disk drive to the RAM (main memory) of the computer.
2) How much data the system's RAM can hold?
Factor one is dependent on the connectivity of the drive in the system. Macintosh internal or external ports do not allow more than 5-10 MB/s. Higher speeds up to 80 MB/s are possible by integrating an Ultra 2 SCSI PCI card with an Ultra 2 SCSI drive.
Data Access
Factor two is the key to higher performance. More memory enables more data to be accessed at higher speeds. The transfer rate from RAM to the CPU is a million times faster than the transfer rate between the disk drive and the CPU. For example: The difference between data accessed from PC-100 SDRAM operating at 8 nanoseconds, when compared to 7200 RPM, 8 millisecond SCSI hard drive will be exactly a million times faster than the SCSI disk drive.
Note: One millisecond is equal to 1/1000 (One thousandth of a second) One nanosecond is equal to one 1/1000000000 (One billionth of a second)
The difference between data accessed from RAM and the disk drive is (1/1000000) (One millionth of a second).
Therefore, maximizing RAM is the most inexpensive performance upgrade possible.
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