Hard Drive encoding?

[mikehende]

I am having trouble understand some concepts of this topic guys, can any of you here simplify "timing bits","MFM-Modified Frequency Modulation", "RLL" and "PRML" for me please?

[tonyd]

I'm familiar with Frequency Modulation (FM) when it comes to radio transmission. It's a method of putting information on a radio wave. They take the radio wave, a signal that can be electronically transmitterd, let's say 88.5 MHz, and vary the frequency by let's say, the frequency of human audio - 20 Hz to 20 KHz. When your electronic receiver tunes into the 88.5 MHz radio wave, it looks for the variation in frequency to decode the audible tones which are reproduced by the radio's sound system.

That's very simplifed. Anyway, I don't know how it relates to hard drive encoding. But maybe it helps.

[mikehende]

Yes, it does, every little bit helps, thanks!

[Pi rules]

Well, MFM (http://www.webopedia.com/TERM/M/MFM.html) is an older encoding scheme used (still?) by floppies and old hdds, and was replaced by RLL (http://www.webopedia.com/TERM/R/RLL.html), allowing larger hdd capacity and faster access time.

PRML converts analog signals read by the hard drive head from the platter to digital signals (I think).

Just curious, are you reading some sort of certification book? Just wondering because I might this summer and see if I can get a cert. or two.

Edit: There is some pretty interesting hard drive encoding & decoding information here (http://www.storagereview.com/guide2000/ref/hdd/geom/data.html) with what you asked and more.

[mikehende]

Yeah, I am studying the Mike Meyers "All in one guide" A+ Certification Book [5th edition], which seems to be the A+ Bible and is a great book in itself but I always do extra research whenever I get to something that puzzles me in the book at which time I use the Cert forum which deals specifically with the A+, if I am not satisfied with the answers there on any particular topic then I come here, otherwise I always come here for all non-exam help with pc's in general.

Thanks for the link, got that one already as it is referred to in the book, appreciate the explanations above.

.

[mikehende]

Another HDD issue, some people are telling me that HDD's are universal for desktops and laptops have their own universal types of HDD's. I don't see this, had an Acer here the other day and tried fitting a HD from a Dell 5100, would not fit. What's yuor take on this guys?

[kelly]

Physically: 3.5" drives are standard for desktops, 2.5" are standard for laptops.
Electrically: IDE/EIDE are standard for both, until recently when SATA are being installed in desktops. Haven't seen any 2.5" SATA's, but that doesn't mean they're not out there.

[mikehende]

why are the desktop drives called 3.5"?

[kelly]

It's the size of the platters.

[mikehende]

I have this Hp pc which has a HDD that reads as ATA 133, it is much slimmer than the other regular HDD's I have, I tried replacing the HDD with a regular IDE but it won't fit into the cage so I guess I can make some modifications and adjustments to get it to fit snugly into the cage, question, is this recommended or should I get another ATA 133 drive to replace?