rc@garbo.EBay.Sun.COM (Ran-Chi Huang) (02/26/91)
Hi NetLanders,
I'm fascinated with the so-called IDE drives. I understand that the
only thing a user has to do is to select a drive type closest to the
capacity of the actual device during the CMOS setup, and the IDE drive will
happily emulate that particular drive type. How is that done ?
Specifically, I like to know the followings:
1. When does the drive figure out what to emulate ? At boot time ?
2. Who does the track/head/sector remapping ? The controller
hardware, or the so-called expansion BIOS. Can somebody
describe what involves in the initialization phase and normal
I/O operations ? Like reading the CMOS RAM, blah, blah...
3. Does that mean IDE drives depend heavily on the DOS operating
environment in order to function ? If the drive fails to
figure out what to emulate, does it act like a generic ST506
disk controller ?
4. Now, the actual disk is a total black box as far as a user is
concerned. What does a (high-capacity) disk look like,
physically ? Does it use the standard ST506 data transfer rate ?
Does it use a zone encoding technique, i.e. putting more sectors
on outer tracks, to increase overall capacity?
Thanks for all the information you can provide.
--
Ran-Chi Huang BELL: (408) 276-5832
Sun Microsystems, M/S 3-03 DOMAIN: rc@EBay.Sun.COM
1355 California Circle UUCP: ...!{sun}!rc
Milpitas, CA 95134rafiq@ccu.umanitoba.ca (Salik "slick" Rafiq) (02/26/91)
In article <5222@male.EBay.Sun.COM> rc@garbo.EBay.Sun.COM (Ran-Chi Huang) writes: >Hi NetLanders, > > I'm fascinated with the so-called IDE drives. I understand that the >only thing a user has to do is to select a drive type closest to the >capacity of the actual device during the CMOS setup, and the IDE drive will >happily emulate that particular drive type. How is that done ? > [Bunch of questions deleted] > >Thanks for all the information you can provide. Most of your questions are answered in the March '91 BYTE (which just arrived in my mailbox today). Salik. -- Salik Rafiq internet: rafiq@ccu.UManitoba.CA Department of Computer Science rafiq@gold.cs.UManitoba.CA University of Manitoba BITNET: rafiq@UOFMCC Winnipeg,Manitoba
reid@hplvec.LVLD.HP.COM (Reid Trimble) (02/27/91)
In comp.sys.ibm.pc.hardware, rc@garbo.EBay.Sun.COM (Ran-Chi Huang) writes:
I'm fascinated with the so-called IDE drives.
<< other stuff deleted, basicly: how do they work >>
---------
Check out the latest issue (March '91) of Byte magazine. In the
"Hands On" section (I think) there's a great article that addresses
all your questions and more.neese@adaptx1.UUCP (02/27/91)
>/* ---------- "How does an IDE drive work ?" ---------- */ >Hi NetLanders, > > I'm fascinated with the so-called IDE drives. I understand that the >only thing a user has to do is to select a drive type closest to the >capacity of the actual device during the CMOS setup, and the IDE drive will >happily emulate that particular drive type. How is that done ? >Specifically, I like to know the followings: > > 1. When does the drive figure out what to emulate ? At boot time ? Some drive do it on the fly. Other read the paramters at boot time and others have switches to figure it out. The best way to know about how each drive does it is to get the OEM manual for that particular drive. > 2. Who does the track/head/sector remapping ? The controller > hardware, or the so-called expansion BIOS. Can somebody > describe what involves in the initialization phase and normal > I/O operations ? Like reading the CMOS RAM, blah, blah... The controller on the drive does the remapping. As far as initialization goes, it is best explained in the OEM manual for each drive. It varies from drive to drive. But basic init is done by the system BIOS by the code that did the init for standard disks. IDE drives are *supposed* to appear to the systems just like the standard ST506/MFM drives/controllers do. > 3. Does that mean IDE drives depend heavily on the DOS operating > environment in order to function ? If the drive fails to > figure out what to emulate, does it act like a generic ST506 > disk controller ? IDE drives do not depend on DOS for proper operation. If the drive is engineered correctly it will appear to be a standard ST506 MFM controller. > 4. Now, the actual disk is a total black box as far as a user is > concerned. What does a (high-capacity) disk look like, > physically ? Does it use the standard ST506 data transfer rate ? > Does it use a zone encoding technique, i.e. putting more sectors > on outer tracks, to increase overall capacity? As far as transfer rate goes,....it really doesn't matter how slow or how fast the data transfer rate is. As all data transfers take place via PIO through the system bus, the system will take/send the data as fast as the drive will send/receive the data. The drive regulates the data transfer rate, much like SCSI drives do the same thing. The data rate to/from the drive will be at the rate of the encoding scheme. The encoding scheme is completely transparent to the system. Roy Neese Adaptec Senior SCSI Applications Engineer UUCP @ neese@adaptex uunet!cs.utexas.edu!utacfd! {nominil,merch,cpe}!adaptex!neese uunet!mlite!adaptex!neese