[BBC-Micro] Hard or Soft Sectored Drives

Jules Richardson julesrichardsonuk at yahoo.co.uk
Fri Dec 22 10:59:40 GMT 2006


Pete Turnbull wrote:
> On 22/12/2006 09:21, David Harper wrote:
> 
>> Hard sectored disks had a physical mark at each sector. This meant a whole 
>> ring of index holes, one for each sector, rather than just a single hole to 
>> mark the start of the track.
>>
>> I have not seen one of these disks for a very long time. IIRC the technique 
>> was used for the old 8-inch floppy disks. (We are talking early 1970's 
>> technology here, before 5.25-inch disks were thought of.)
> 
> Some 5.25" disks use the same technique, and were available in either 
> 10-sector or 16-sector types.  8" disks typically used either 26 
> sectors, or occasionally 32 sectors, though the earliest used only 8. 

I'd always thought of it as any track-based sectoring scheme which was imposed 
upon the end user and couldn't be changed in software - whether the sector 
marks were dictated at the factory somehow (e.g. by sector holes in a disk), 
or whether they were fixed by the device firmware at format time.

In other words, 'hard sectored' could apply to floppies, some forms of optical 
media, certain types of hard disk, and perhaps even certain types of tape 
(although that may be stretching the definition a little, but most tapes are 
essentially just a single track of sectors :)

> It's a bit different on hard drives, as they don't have index holes.  In 
> fact, on some hard drives, like the 12" Fujitsu winchesters on one of my 
> PDP-11s, they can be programmed for any of several numbers of sectors, 
> and different sector sizes.  On some multiple-platter disks, this is 
> done by having one surface dedicated to holding sector identifiers.

Now that I would call soft-sectored. But what about an IDE drive which always 
uses the same geometry internally, even though it may translate this and 
present a different geometry to the user? For all intents and purposes it's 
hard sectored because the physical sectoring scheme doesn't change when the 
media is formatted.

cheers

Jules



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