hartvig@diku.UUCP (Hartvig Ekner) (07/07/87)
I'm using a DTC-5150BX harddisk controller with my Hitachi DK521-5 drive,
and I would like to choose another interleave factor. Does anybody know
if it's possible and how to do it? I don't have the manuals for the
controller since I bought it second hand. I would also like to know how
to specify bad sectors, since the format program doesn't find all the ones
supposed to be on the drive (in fact is doesn't find ANY at all, and there
are about 25 bad sectors on the drive. This must mean that Hitachi are
VERY conservative when they locate bad sectors).
Here's another one for your controller gurus:
How come it's hard to get above 120 kbytes/second with hard-disk controllers?
How about this sector numbering:
1 10 2 11 3 12 4 13 5 14 6 15 7 16 8 17 9
Assuming that the controller software has enough time to reload the
HDC's sector register and set up everything for the DMA transfer in a
full sectors time this track should be read in two revolutions of the disk.
Again assuming that the track-to-track time is less than one revolution
(16.66 mS) and 6 tracks pr. cylinder it should be possible to read a full
cylinder in 2*6 + 1 = 13 revolutions, or 4.6 cylinders pr. second.
4.6 cylinders/second * 6 tracks/cylinder * 17 sectors/track * 512 bytes/sector
= 235 kilobytes/second
------------------------
Why don't all hard-disk controllers achieve this speed? I have even seen some
with a peak transfer rate of 40 k/second. Come on guys! This is equivalent
to only 1.3 sectors read pr. revolution of the disk!!!!!! Are the sectors
arranged backwards or what :-)
By the way, I can really recommend the Hitachi disk drive. It's a half height
40M voice coil drive with 25 mS average access time (45 mS full stroke and
6 mS track-to-track). The drive is built VERY nicely (both mechanical and
electrical) and it also parks the heads automatically at power off. All
this to achieve a MTBF of 30000 POH......
Hartvig Ekner ....mcvax!diku!hartvig