[Simh] generated tape images

[J. David Bryan]

On 28 Jul 2005 at 15:41, Rich Alderson wrote:

> It does not appear that simulated tape drives will create multiple tape
> images when the output stream is larger than a single tape "should"
> hold. 

I implemented this for the HP 7970 drives (see "HP2100/hp2100_ms.c" in the 
source distribution; search for "TCAP" to see how it's done).  For example, 
one may do:

  SET MSCx REEL=600

...to cause an EOF after about 600 (or 1200, or 2400) feet of simulated 
tape are used.  In the absence of a REEL command, or if REEL=0 is 
specified, then the tape is of "unlimited" length.

Essentially, I call "sim_tape_eot" in the base SIMH tape simulation library 
to check if the current position is beyond the calculated capacity.  The 
latter is simply reel size in inches multiplied by tape bytes-per-inch 
density.  Note that the reel size is pessimistic -- more data will fit than 
the reel size would indicate -- because IRGs and EOF gaps aren't tracked 
(although they could be; might be a nice option for the tape library).

Adding reel sizes to the HP tape drive took about two lines of code, 
exclusive of the UI.

                                      -- Dave