On Tue, 20 Feb 2018 07:46:45 +0000, Chris Bartram wrote:

On 20/02/2018 05:05, Johnny B Good wrote:
On Mon, 19 Feb 2018 10:08:25 +0000, Chris Bartram wrote:

====snip====


Digital audio ripping is very variable according to disk quality and
drive ability, and i've found that reading one dodgy disk can then
slow down subsequent rips until after a reboot.

That sounds like a Microsoft Windows experience.

Actually, recently on Linux. One CD, seemingly undamaged, just refused
to rip, sticking at one point, and then the next one was slow. I was
wondering if the first one was one of those deliberately nobbled ones
from the early 2000s.


The cause was due to the driver code detecting a high error rate,
causing it to drop back to a lower UDMA performance mode, one stage at
a time in the hope of easing the stress on the interface to eliminate
the high rate of errors until finally resorting to the least
stressful[1] of all modes, PIO mode, which once selected, could not be
reverted back to UDMA mode automatically.

If the driver had dropped from UDMA mode 3 down to 2 then 1 before
eliminating the high rate of errors, it could automatically revert back
to the faster UDMA modes provided it hadn't resorted to PIO mode. The
idea behind this behaviour was to automatically select the fastest
reliable UDMA setting with hard disk drives since not all drives fully
or reliably met their claimed UDMA specification.


I've seen all that in the past, but in this case it feels like drive
firmware setting a read rate. That's just a guess, obviously, without
delving very deep. From what I recall, PIO dropback on Windows with an
optical drive survived a reboot?

That was my experience (shared by all windows users) who suddenly found
problems playing DVD videos due to the optical disk drive transfer mode
dropping into PIO mode, seemingly "Out of the Blue", for no obvious
reason and remaining in that mode even after a reboot.

It required the user to take remedial measures to restore it back to a
UDMA mode (typically modes 1 or 2 in the case of a DVD drive, rarely, if
ever, modes 3 and above, which was the preserve of the later models of
hard disk drive).

Of course, SATA has largely eliminated this problem since it can
distinguish between media and interface errors (and even allow hot
swapping a SATA interface cable without crashing the drive interface - a
luxury not provided for with IDE). SATA isn't going to try to remedy
media issues by futilely slowing down the interface.

--
Johnny B Good