> MFM and RLL are encoding schemes. They define how to turn a stream of 0's
> and 1's into the magnetic patterns on the disk. They have nothing to do
> with how a drive talks to its controller
Of course, I was just using the vernacular... (About like "CMOS setup" -
you didn't make any comments about that one though. :-)) But I didn't
remember that it was called ST506. Sounds like a Seagate part number.
Was it a PC hard drive, or even earlier?
> When you low-level format a disk, you write the sector headers and sector
> data onto the disk. The sector headers typically contain information as
> to which sector this is.
>
> > MFM drives usually use one side of one platter just for these marks
>
> Not normally. The sector headers are stuck in between the data blocks,
> just like on a floppy disk.
>
> You're probably thinking of the servo bursts - the signals that keep the
> heads on a track. Some drives did use a particular side of one of the
> platters for these. Other drives 'embedded' them in the sector headers on
> the data platters. The latter is not common on ST506 interfaced drives,
> but is common on SCSI/IDE drives
Hmmm, interesting. So low-level formatting doesn't rewrite these?
That would imply that the servo bursts are not involved in determining
sectors at all. I used to use an RLL card with a couple of formerly
MFM drives, and it made more sectors per track, so I thought the
wasted platter had something to do with that.
> >
> > On a PC, if you need to low-level format an MFM drive there are several
> > options. Starting with the original XT controller, IBM set the standard
> > that BIOS code for doing that formatting would always start at a particular
> > address. So, you could use DOS's debug utility to simply execute the
>
> Are you sure: While almost all clone controllers have a formatter routine
> at C800:5,
Yep, that's the one.
> I couldn't find it in the original IBM XT hard disk BIOS.
Hmmm. Well I think I remember using a full-length IBM controller with a
30 meg drive, and only being able to format 10 megs of it because it was
the XT controller designed for the 10 meg hard drive. But I don't remember
if I used debug to format it, or something else. This is my mom's machine
which she never uses, so one of these days I can replace it with something
more useful and refesh my memory about its contents. I'm going to try
to restore it to original condition since it is so close already.
>
> Atari's are not my speciallity, but I seem to remember that the ST has a
> 'DMA port' which is somewhat SCSI-like. Most ST hard disk systems were a
> SCSI host adapter followed by a SCSI -> ST506 (or whatever) interface
This guy's machine wasn't an ST I don't think, but that is what I have.
--
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(_ | |_) Shawn T. Rutledge on the web: http://www.goodnet.com/~ecloud
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Received on Wed Jun 03 1998 - 13:34:45 BST