Pertec Tape Drive Interface Musings

Johnny Billquist bqt at
Wed Jun 10 14:31:21 CDT 2015

On 2015-06-10 16:32, Dennis Boone wrote:
>   > I don't think it really is that you have a long gap when you rewrite
>   > a "bad" block per se. But you get long gaps when you stop/start. And
>   > a rewrite implies that you will get a stop/start situation.  But in
>   > case you already were going stop/start, the gap will not be extended
>   > any longer.
> Some drives will back up, get up to speed, read the end of the previous
> block, switch from write to read when the irg goes by.

I think they all back up and then start accelerating. But how precise 
can you make the acceleration? And how fast can you switch from read to 
write? All drives I've worked on created long gaps if they appended a 
new block from standstill.

> The size of the irg can vary upwards from a minimum spec, at least in
> drives that try to stream, as they will keep the tape running for a
> moment in hopes that data will arrive to be written.



Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol

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