- The size: I need more, more...

- Very well, nice...: and bargain sale?

- Interface IDE

- Who needs SCSI?

- To turn and to rotate, everything is to start...

- UltraDMA/66

- Do not be ancient: be updated!

- Conclusion

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Hardware for the summer - autumn 1999


Interface IDE

Good, the truce was finished: there we go with the initials and the technological topics. IDE is the name of the interface most used for the connection of hard disks (and CD-ROMs) in the computers. So common it is, that for many years (from ends of the almost forgotten one it was the 486) all the basic badges incorporate the checker integrated IDE.

So it can be said that the first IDE advantage is that we already have it, it does not cost anything (good, it costs him what the motherboard, free there is nothing). The second IDE advantage is that the hard disks that use this technology are cheaper than the hard disks that SCSI uses. Finally, it turns out to be slightly easier to install a hard disk IDE that one SCSI, although the difference is not abysmal.

Connectors for hard disks (top part; two channels IDE, one for connector) and disk drive

Disadvantages? Well, the first one is that normally in a computer only 4 devices IDE can settle, 2 for every channel IDE, assuming that the checker is EIDE (Extended-IDE), which is not great to take up office since it is the habitual case in integrated checkers or with less than 4 years. It is possible that they seem sufficient to him, but think that with the hard disk and a breeding animal of CD - ROM he already only has left 2 free positions... that in fact they are usually sufficient for most of users, but not for all, especially if he decides to install a unit Zip or internal SuperDisk and/or a CDs tape recorder.

The second atañe at the speed, although of a peculiar form. The people usually say that "the hard disks IDE are slower than the SCSI", which is not true, but it is usually true, although sometimes it is the other way round. Cómooo? Calm, we explain ourselves:

  • The hard disks SCSI, due to his vocational guidance, tend to incorporate very much earlier the technological advances and to have top services, for what they are usually of for better than themselves the IDE, independently of the interface, apart from being clearly top in certain specific applications.
  • Nevertheless, the hard disks IDE can be equal of rapids that the SCSI, whenever it is a question of hard disks with a similar mechanics (this is, which only differ in the connection interface, but which turn at the same speed and his access times are similar).
  • And even, in case of modern hard disks of similar characteristics, in a computer with the only hard disk it is possible that IDE is even more rapid than SCSI, since SCSI is thought for several devices and for multitask, what needs a certain load of work that is wasted in case of using only a hard disk and the only application.

For it, the user ofimático or servant has not even to raise it: what he needs is a hard disk IDE, SCSI simply is not foreseen for these uses and it will not offer him any advantage. Only remember that if it has more than one device, it must place them in different channels, especially if one of them is slower than other (as it happens with the CD - ROM).

How to know if they are in different channels? Nothing easier: every channel uses a cable, so if they are in the same cable it is that they use the same channel, in whose case buys another cable (they are very cheap) and put them in different channels (and I did not forget to form them like master's degree or slave; consult the Topics Related for more information in this respect).

Who needs SCSI?

Simply, who is going to use many devices in his computer, or I needed to make a big simultaneous use of the same ones, or used multitask of massive form. In such cases, SCSI has no rival; it distributes to the perfection the bus breadth between the diverse devices, allows a completely simultaneous use of the bus (what is not possible in IDE, except using different channels) and in addition it loads very little work in the microprocessor, unless checkers of low quality are used.

The typical case of use of SCSI is that of a servant of files, who needs to answer to numerous simultaneous requests, with dispersed information probably on several hard disks (SCSI allows up to 15 devices). Cases less extreme that SCSI might need would be the users of programs of edition of video or those of programs CAD, although perhaps they had the above mentioned sufficient with a hard disk IDE of high scale.

Two topics that must not be careless at the time of buying devices SCSI are the type of used norm and the speed of rotation of the hard disk. At present only two norms are used for hard disks SCSI: the Wide SCSI and the Ultra-2.

  • The norm Wide SCSI (really "UltraWide SCSI") defines a connection of 16 bits at a 20 MHz speed, what with a skillful calculation takes us at a speed of 40 Mb / century theoretical maximum transference This is usually sufficient when we treat with the only hard disk, that scarcely it will overcome 20 MB/s in brief blasts, but it turns out to be insufficient if we use several devices.
  • The norm Ultra-2 (Ultra-2 Wide SCSI, to be correct) doubles the speed of the previous one, coming up to 40 MHz, what with a bus of 16 bits 80 MB/s does, completely unattainable enormous number for the only hard disk but nothing exaggerated for computers with two or more devices SCSI.

Type of norm SCSI

Maximum transference with 8 bits

Maximum transference with 16 bits (ways Wide)


5 MB/s

Not applicable

SCSI-2 or Fast SCSI

10 MB/s

20 MB/s

Ultra SCSI or Fast-20

20 MB/s

40 MB/s ("Wide SCSI")

Ultra-2 SCSI or Fast-40

40 MB/s

80 MB/s ("Ultra-2")

My recommendation is to be decided by discs Ultra-2, especially bearing in mind his scarce price difference opposite to the Wide SCSI. Certainly the checker can that it gets dearer a little, but it is not a device in which it is possible to curtail. If she is a better checker in card or integrated to motherboard, it is only a tastes topic; the integrated slope less and it is a "cleaner" solution, although if the motherboard breaks the grief is monumental.

As for the rotation speed, I send them to the following paragraph, although in short I will say that nowadays to buy a hard disk SCSI of less than 7.200 rpm is "to do the cousin", so one report of what he buys, do not sell to him an antiquated hard disk.

To turn and to rotate, everything is to start...

Yes, I am in a good mood, so be glad that they get out from hearing me singing. Since everybody knows (?), the rotation speed is one of the fundamental parameters on a hard disk, since the more rapid it turns, the major is the information transference.

Very well, in fact it is not so simple, it depends on if the information is in the center or in the periphery of the disc (as any Physics student knows or the one who has mounted in a merry-go-round), on the number of heads and discs and of his disposition, of the buffer, of the access times... but in general it is something very important. If in 1.997 the hard disks "of consumption" were turning 4.500 rpm (revolutions per minute, of course) and in 1.998 they were doing it to 5.400 rpm, in the middle of 1.999 the hard disks begin entering strongly 7.200 rpm.

On the market SCSI, which as we were saying it is much faced to the professional thing, all the discs are (or they should be) of 7.200 rpm, and even monsters exist to 10.000 rpm, which seems almost dangerous, the truth (the engine of my car usually turns enough more slowly). On the market IDE there seem to be two classes of discs:

  • discs to 5.400 rpm, with enormous capacities at a ridiculous price;
  • and discs to 7.200 rpm at a price perceptibly higher (many manufacturers make two different scales according to these typical, like Digital Western with the series Caviar-5.400 rpm - and Expert-7.200 rpm - or Seagate with the Medalist and Medalist Pro).

What is better? It depends on his priorities, there is no clear answer. Now then, a good disc IDE to 7.200 rpm can be perfect if what he needs is to mount a CAD job and does not want to pay out what SCSI costs, for example; although it bears in mind the IDE limitations, a servant is sure to 95 % who will need SCSI.

Certainly, 7.200 rpm is the whole number, undoubtedly, what is evident in the big quantity of heat that these aparatitos generate due to the friction; it does not even happen to him to touch them when they have lit a little bit, one might hurt enough. It is for it that it does not turn out to be any foolery to place a fan to cool them a little, although he remembers that if the heat cannot go out of the box of the computer it will not serve as anything.


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