Hard disk track layout

Interleave 3

• Gap1 = 16
• Gap2 = 3
• Gap3 = 22
• Sync = 13
• Count = 32
• Size = 2*128

Gap 1

16 x 4e 

Sector 0

13 x 00
IDAM a1 fe | 00 00 00 01 | CRC f1d3 
3 x 4e | 13 x 00
DAM a1 f8 | 256 x e5 | CRC e5b4 
3 x 00 | 19 x 4e

Sector 11

13 x 00
IDAM a1 fe | 00 00 0b 01 | CRC 2d29 
3 x 4e | 13 x 00
DAM a1 f8 | 256 x e5 | CRC e5b4 
3 x 00 | 19 x 4e

Sector 22

13 x 00
IDAM a1 fe | 00 00 16 01 | CRC 5806 
3 x 4e | 13 x 00
DAM a1 f8 | 256 x e5 | CRC e5 b4 
3 x 00 | 19 x 4e

...

Gap 4

340 x 4e 

Gap 4 is actually truncated by the passing index mark.

Size of a track:

• With a 10 MHz clock for HD, the cell size is 100 ns.
• With 3600 Rpm we have a track length of 16.6667 ms. This means we have a maximum of 166667 cells.
• With 16 bit per encoded byte we get 10416 bytes as the maximum (unformatted) capacity.

Size per sector: 319 bytes

All sectors: 10208 bytes

With Gap 1 being 16 bytes long this leaves 192 bytes for Gap 4.

Track 0	0	11	22	1	12	23	2	13	24	3	14	25	4	15	26	5	16	27	6	17	28	7	18	29	8	19	30	9	20	31	10	21
Track 1	0	11	22	1	12	23	2	13	24	3	14	25	4	15	26	5	16	27	6	17	28	7	18	29	8	19	30	9	20	31	10	21
Track 2	0	11	22	1	12	23	2	13	24	3	14	25	4	15	26	5	16	27	6	17	28	7	18	29	8	19	30	9	20	31	10	21

...

Interleave 4

• Gap1 = 16
• Gap2 = 3
• Gap3 = 22
• Sync = 13
• Count = 32
• Size = 2*128

Track 0	0	8	16	24	1	9	17	25	2	10	18	26	3	11	19	27	4	12	20	28	5	13	21	29	6	14	22	30	7	15	23	31
Track 1	0	8	16	24	1	9	17	25	2	10	18	26	3	11	19	27	4	12	20	28	5	13	21	29	6	14	22	30	7	15	23	31

...