Disc drive with reduced write latency
A disc drive with a disc having multiple concentric data tracks. A track start point is rotationally displaced by a track skew time relative to a track start point of an adjacent concentric data tracks. The read/write head has a write settling time that is more than the track skew time. A data reordering circuit and firmware reorders write data and provides the reordered data to the read/write head after the write settling time. The reordering of the write data reduces write latency.
1. A process of performing a sequential write operation in an apparatus, comprising:
calculating a sector number “K” of a next track where a next sequential write operation begins;
reordering data to be written on the next track from an order of sectors 0 . . . M in numerical sequence to a reordered data sequence of sectors K, (K+1), . . . M, 0 , 1 , 2 , . . . , (K−2), (K−1), the reordering reducing write latency angle waiting for alignment with a sector during the write operation;
writing the reordered data on the next track starting at sector K and finishing at sector (K−1); and
generating error correction codes for the reordered write data based on physical sector numbers of the sectors during the write operation.
2. The process of claim 1 wherein the calculating takes into account a settling angle needed for a write operation after the start of a seek operation.
3. The process of claim 1 wherein the calculating also takes into account the last sector number written on the last track and the amount of skew between the tracks.
4. The process of claim 1 comprising starting the writing after a write settling angle.
5. The process of claim 1 further comprising setting an errors correction code seed for each sector according to a physical sector register.
6. The process of claim 1 further comprising writing data through the track start point without stopping sequencing.
7. The process of claim 1 further comprising writing write data in a write buffer in an order controlled by a table of linked lists.
8. The process of claim 1 further comprising writing the write data in a write buffer.
9. The process of claim 1 further comprising pointing to data that is to be written into sectors with a access pointer.
10. An apparatus, comprising,
sectors; and
a controller circuit reordering write data, the reordering reducing write latency angle waiting for alignment with a sector; the controller circuit generating error correction codes for the reordered write data based on physical sector numbers of the sectors during a write operation wherein the write data is reordered from a sequence arranged 0 . . . N corresponding with 0 . . . N sectors starting with sector 0 at the track start point to a reordered sequence K . . . N, 0 . . . (K−1) where sector K is a first physical sector written after the write settling angle.
11. The apparatus of claim 10 wherein write operations of the reordered data including error correction codes based on physical sector number at a next sector are started after a write settling angle.
12. The apparatus of claim 10 wherein an error correction code seed for each sector is set according to a physical sector register.
13. The apparatus of claim 10 wherein data is written as the read/write head passes through a track start point without stopping sequencing.
14. The apparatus of claim 10 wherein write data is written in a write buffer in an order controlled by a table of linked lists.
15. An apparatus, comprising:
sectors; and
means for providing reordered write data, the reordering reducing write latency angle waiting for alignment with a sector during a write operation, and for generating error correction codes for the reordered write data based on physical sector numbers of the sectors during a write operation wherein the means for providing reordered write data reorders the data from a sequence arranged 0 . . . N corresponding with 0 . . . N sectors starting with sector 0 at the track start point to a reordered sequence K . . . N, 0 . . . (K−1) where sector K is a first sector written by the read/write head after the write settling angle.
16. The apparatus of claim 15 wherein the means for providing reordered write data starts write operations of the reordered data including error correction codes based on physical sector number at a next sector accessed after a write settling angle.
17. The apparatus claim 15 wherein the means for providing reordered write data sets an error correction code seed for each sector according to a physical sector register.