Karbosguide.com - Module 4b4.

Harddisks developments - continued

Speed generates heat

Some years ago there was a problem with noise. I had to give up a Quantum SCSI-based disk, which turned at 7200 RPM with the sound of a dentist's drill. It was intolerable to be in the same room!

The best SCSI disks available rotate at 10,000 and 14,000 RPM. They are expensive but ultimately they provide the highest transfer capacity.

Check this company for hard disk cooling gizmos. Here is one:

The controller principles

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Further down this page is a review of the interfaces which are used for hard disks. But, first look at this brief summary:

Controller Description
MFM, RLL
and ESDI Older standards for hard disk interface
IDE Simple, primitive interface. Data are delivered on the ISA bus, resulting in low transfer speed. Disks < 528 MB. Is not used on new PCs.
EIDE Improvement of IDE. Data are delivered on the PCI bus with Bus Master control, which results in high transfer speed. Large disks (currently up to 40 GB). Room for four units, which are typically connected directly to the system board. Inexpensive and effective disks. Ultra DMA is the best interface among the EIDE varieties.
SCSI High end controller system, where the units are connected to a special (expensive) controller. The hard disks are generally of highest quality, fast and with a long life span. An ordinary SCSI controller can run 7 hard disks each of 45 GB - or more. The latest IBM Ultrastar 72ZX holds 72 GB and a cache of 16 MB.

All together we have several technologies which all can be optimized for making better hard disks:

Learn more
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Also see Module 4c1 about optical media (CDROM and DVD).

Controller	Description
MFM, RLL and ESDI	Older standards for hard disk interface
IDE	Simple, primitive interface. Data are delivered on the ISA bus, resulting in low transfer speed. Disks < 528 MB. Is not used on new PCs.
EIDE	Improvement of IDE. Data are delivered on the PCI bus with Bus Master control, which results in high transfer speed. Large disks (currently up to 40 GB). Room for four units, which are typically connected directly to the system board. Inexpensive and effective disks. Ultra DMA is the best interface among the EIDE varieties.
SCSI	High end controller system, where the units are connected to a special (expensive) controller. The hard disks are generally of highest quality, fast and with a long life span. An ordinary SCSI controller can run 7 hard disks each of 45 GB - or more. The latest IBM Ultrastar 72ZX holds 72 GB and a cache of 16 MB.