BOYD@ENR.Prime.COM (05/25/90)
Although you seem happy, The start of a track is not NECESSARLY the start of a sector. (Tracks have internal information prior to the start to the first sector. These include track id and state information such as bad track etc.) Larry Boyd BOYD@ENR.PRIME.COM
dhesi%cirrusl@oliveb.ATC.olivetti.com (Rahul Dhesi) (05/26/90)
The index hole marks the start of the overhead data that begins a track. The first sector does not start until some bytes later. Rahul Dhesi <dhesi%cirrusl@oliveb.ATC.olivetti.com> UUCP: oliveb!cirrusl!dhesi
glenn@cs.utexas.edu (Gwangwu Lai) (05/26/90)
Eric Sheppard wrote: | Now who's in left field, here? He said that if it determined the start of a | sector, there would be many such holes around the center. I told him that's | what they USED to do, until they developed soft sectoring. Bill Davidsen replied: * That's correct, a hard sector disk has multiple holes. As I recall it *also has an index hole, but I haven't worked with hard sector in... *maybe ten years. As I recall it, a hard-sectored disk had an index hole and multiple sector holes. The sector holes were evenly spaced around the hub, while the index hole was located approximately half way between two sector holes. Glenn
del@fnx.UUCP (Dag Erik Lindberg) (06/02/90)
In article <3000@se-sd.SanDiego.NCR.COM> lord@se-sd.SanDiego.NCR.COM (Dave Lord) writes: =In article <9625@hydra.gatech.EDU> ce1zzes@prism.gatech.EDU (Eric Sheppard) writes: =}on an IBM diskette, the small hole near the center of the diskette is used =}to indicate A) the start of a track B) the start of a sector. = =}My answer (B) was judged incorrect, and my debate with the instructor would = =}what they USED to do, until they developed soft sectoring. The index hole =}shows where the FIRST sector is located, and it's up to the DOS to determine =}where the rest are. = =Sounds to me like you're the one who's out to lunch here. You admit that =the index hole marks the start of the first sector but deny that it =marks the start of a track? I can see why your professor is not buying. The index hole does not necessarily indicate the start of the FIRST sector. It does indicate the start of the track. Define "IBM diskette". If you mean a diskette as formatted on an IBM PC compatible computer running PC DOS then coincidently the index hole will also indicate the start of the first sector. However, the IBM specification does not require this, and you can get improved performance by formatting the diskette with 'sector skew', this is in addition to 'sector interleave'. The sector skew is the offset from the start of the first track to the first sector on the track. This allows for the step motion of the head to stabilize before the first sector of the track comes around under the head. Using this method of formatting (and several systems do) results in a different sector being located following the index hole on consecutive tracks! These disks follow the IBM specification, and can be read/written on PC clone machines running 'DOS' with slightly improved performance over the 'normal' formatting scheme. -- del AKA Erik Lindberg uunet!pilchuck!fnx!del