> On Feb 3, 2021, at 1:27 PM, Al Kossow <[email protected]> wrote:
>
> On 2/3/21 10:18 AM, Paul Koning wrote:
>
>> Fair enough, but that means your real time processing needs to be sufficient
>> to know where the tracks are. And if the media are in bad shape, you may in
>> fact want to capture each track N times at slight offsets from the nominal
>> position, then do signal processing to recover the data as best you can.
>
> That is in conflict with the requirement you spend as little time as you can
> on shedding media
> ideally, you'd use a 96tpi drive on 48tpi and microstep the head positioner.
> you still have the
> problem of head clog.
>
> And, AFAIK, no existing software does any of this.
Which might mean either (a) what I suggested is in practice not needed, or (b)
existing software treats as unrecoverable disks that could be recovered with
more sophisticated tools. I have no idea which is correct.
>
>> Come to think of it, the techique of reading 1/2 inch tape with 36 track MR
>> heads is somewhat similar: you get multiple readings of the same nominal
>> data track and can use the additional data to help with recovery.
>
> In practice, the channels smear together, that's why John Bordynuik went to
> 36 tk 3490 heads from 18 tk 3480 heads on his 1/2" tape setups.
>
> We saw this as well on the 6-track Whirlwind tapes using a 9-track head.
> Fortunately 6 of the heads lined up cleanly.
Yes, I was thinking of that issue while looking into how a 10 track tape would
look to, say, a 16 track instrumentation recorder head. The picture looked
marginal at best.
paul
