Re: [TUHS] [simh] 2bsd tarball

[Johnny Billquist <bqt@softjar.se>]

On 2020-07-29 15:17, Paul Koning wrote:
> 
> 
>> On Jul 29, 2020, at 5:50 AM, Johnny Billquist <bqt@softjar.se> wrote:
>>
>> Just a small comment. Whoever it was that thought DECtape was a tape was making a serious mistake. DECtapes are very different from magtapes.
>>
>>   Johnny
> 
> Depends on what you're focusing on.  Most tapes are not random-write.  DECtape and EL-X1 tape are exceptional in that respect.  But tapes, DECtape include, have access time proportional to delta block number (and that time is large) unlike disks.
> 
>  From the point of view of I/O semantics, the first point is significant and the second one not so much.

True. But seek times are in the end only relevant as an aspect of the 
speed of the thing, nothing else.

However, seek times on DECtape aren't really comparable to magtape 
either. Because DECtape deals with absolute block numbers. So you can 
always, no matter where you are, find out where you are, and how far you 
will need to move to get to the correct block.
With magtapes, this is pretty much impossible. You'll have to rewind, 
and then start seeking.

   Johnny

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