TK50, was: Re: [TUHS] Ultrix Tape: Block Size?

[Paul Koning]

> On Oct 18, 2018, at 4:31 AM, Christian Corti via cctalk <cctalk at classiccmp.org> wrote:
> 
> On Wed, 17 Oct 2018, Clem Cole wrote:
>> As Paul W pointed out correctly, the TK50 and its children in the DLT*
>> family all used a fixed format 512 byte *blocks on the tape*.    This
> 
> And that is wrong. The TK50 clearly uses variable block sizes. For example, have a look at a RSX11 or VMS tape: ...

Different point.  You're talking about the host programming interface; Clem was talking about the physical representation of the data on the tape.  Clearly it's easy to accept random-length blocks from the host and translate them to a sequence of 512 byte blocks on the media.  SIMH is an example of how that is done: it stores tape images as a count field plus data, laid down in a disk file that internally consists of a sequence of fixed length (512 bytes, traditionally) sectors.

	paul