Disk Control Electronics

When selecting a disk controller you need to be aware of the following things:

1. What type of drive interface does it use?

The two most popular types are EIDE and SCSI. 99% of the new mother boards come with EIDE controller and a multi-I/O built-in. This means that you may not have to worry about any of the rest of this information, for any reason other than your own knowledge and reference to the older motherboards and systems.
EIDE is the best value when comparing size to cost but requires special equipment, the controller, motherboard bios, and drive itself must all be enhanced to really gain the benefits. Drives range in size from 720 MB to 100+ Gigabytes. There are a couple things you might want to consider with the hard drive, but that will be covered in the appropriate section.
SCSI drives tend to be a little more expensive but are available in sizes ranging from 345 MB up to 9 GB, and disk arrays are available to create a drive of any capacity you desire. SCSI controllers also support Scanners, CD-ROM drives, and high speed tape backup devices. SCSI controllers sometimes have a built-in floppy controller but seldom take care of the I/O ports.

2. Does the controller support floppy drives?

Not all controllers have floppy support built in, this is more common on motherboards and SCSI controllers.

3. Does the controller have any built in I/O ports?

Most IDE and EIDE controllers have 2 serial and 1 parallel port built into the controller, where most SCSI controllers do not have any port built in. If your Mother-Board already has these ports built in you must beware not to set those ports to the same addresses as the ports on the controller. You should disable one set or the other - pick the slowest set to disable (if you can).

4. What speed and type of bus does the controller use?

You must be sure that your Mother-Board supports the bus that your controller is using. (i.e. ISA, VLB, EISA, PCI).
The current "standards" are 64 bit, 66, 100, or 133 MHz PCI, which nearly 90% of the motherboards today seem to readily integrate these high-end controllers on the motherboard.
Bottom line, make sure that what you get will run in Windows 95/98 and NT in 32 bit mode. And will give you some future upgradability (even if you never intend to use it - it adds resale value).

5. Does the controller support cache memory? How much?

Cache memory here is completely different that the cache on the mother board, in the CPU, or on the drives. This type of cache allows the CPU to concentrate on processing programs while the controller does the actual searching and retrieving of information from the Hard Disk Drive.
An "index" of the files and their locations are saved in this "cache memory" which can greatly speed up the drive access. Your fastest hard drives and CD-ROM drives have all of this built right in to the drive itself. Only a handful of controllers of cache on them, and these are generally expensive. The amount of cache memory used is entirely user dependent, the more the merrier - generally, there reaches a point where moving to the next level becomes too expensive compared to the performance increase.


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