> How do they handle the issue of how the drive
knows whether it is SS, DS,
> or SS flippy? Or is it assumed that that problem is for the host FDC?
> (some DS drives had both SS and DS index sensors, so that they could read
> SS in the DS drive, and such a drive is going to see TWO index pulses with
> this disk!)
On Thu, 1 Sep 2022, Sellam Abraham via cctalk wrote:
The typical response from the manufacturer is to first
blame the user, and
if that's ruled out, blame the hardware (or vice versa). If both issues
are ruled out, they theny hang up the phone or disconnect the chat, and let
the user call back only to receive another tech who will repeat the
Well, I was speculating about possible engineering solutions, rather than
assignment of blame :-) Tech support can handle THAT.
Obviously, it can be left to the user to mask off any extraneous index
Usually, the OS has its own ways to identify what's there, such as a
"MEDIA ID BYTE" or a data structure (DPB) at a fixed location that will be
accessible disunirregardless of which format it is.
Another way is obviously to do a read from first side. Current approach is
sorta for the OS to check any return codes from the FDC, and display a
message from a table. If it falls through the decision tree, then say
"GENERAL FAILURE" (top brass in 'Nam?)
But, the OS can try a read of the second side. If the first side seems
readable but the second side isn't, then assume SS.
Try an FM read; try an MFM read; try a read at each data transfer rate.
When you achieve success, assume that that's the format.
When I was publishing my Honda book, I had some
battles with the
publisher's editor about whether Honda had
"disc brakes" or "disk brakes".
(also battles about Oxford comma (they claimed that that was archaic!),
and whether to say, "till", "til", "'til", or
"until". (the comma after
"'til" is the "Oxford comma"))
The "Oxford comma" is basically optional in modern writing, but in some
specific cases it makes sense to use it for clarity. However, in law
(specifically contracts) it's imperative. I can't remember the specific
case, but within the last couple of years I remember reading about one
where the lack of the comma meant the court agreed with the workers over
the company and ruled they were entitled to overtime pay.
There are some situations where it is critical for unambiguity. More
often than not, the Oxford comma reduces ambiguity. I USE IT. But, it is
possible to come up with some [relatively rare] examples where it
The publisher's editor had an impressive ability to read a passage, and
come up with a wrong interpretation of it. THAT was very useful, since
once I could rewrite so that he was UNABLE to misinterpret, I could be
reasonably confident that the reader couldn't.
Grumpy Ol' Fred cisin(a)xenosoft.com