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What hard drive technology to choose, SCSI or EIDE? Are SCSI hard drives better than EIDE hard drives? This is a topic of many books and magazine articles. The purpose of this report is to give a somewhat detailed comparison between SCSI (small computer system interface) hard drives and EIDE (enhanced integrated drive electronics) hard drives. EIDE is great a solution for those on a limited budget. If money is no consideration and you're using something more modern than DOS or Windows version 3, SCSI should be your hard drive of choice. Unfortunately, for most of us budget is limited, and there's a real choice to be made between a SCSI based system on one hand, and an EIDE based one with more RAM, a slightly faster CPU or better screen, on the other. You need to weigh the pros and cons in your specific situation. So why purchase SCSI? A single SCSI channel supports up to seven devices. Two channels, for a total of fourteen devices, are becoming more and more common. On the EIDE side of things, four channels are defined, giving eight devices. However, common hardware and software supports only two channels so beyond four devices things become stickier. Real high end devices are available in SCSI drives only. Fairly common examples are extremely large or fast 10,000-rpm hard disks and DAT tape drives. For that reason alone, if you need high speed out of a hard drive, SCSI is your only choice. SCSI supports many different types of devices. The ATAPI (AT Attachment Packet Interface) protocol EIDE can support a fairly wide range as well, but in practice only hard drives, CD-ROMs and tapes are really common. Magneto-optical devices etc. are possible and may eventually become corrupt. Scanners and so forth won't arrive in EIDE versions anytime soon, since it does not support external connections. Summarizing you could say that EIDE meets the needs of the majority, but not all, of the users. EIDE has the problem that it targets the low end market. Some vendors and manufacturers tend to save a dollar too much. This has resulted in badly designed and downright buggy interfaces and chips. The worst excesses appear to be behind us. EIDE PIO (programmed input/output) mode 4 has proven relatively unreliable for a number of reasons.
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