Tape imaging

jim stephens jwsmail at jwsss.com
Thu Aug 11 00:40:51 CDT 2016

On 8/10/2016 9:30 PM, Chuck Guzis wrote:
> On 08/10/2016 08:03 PM, dwight wrote:
>> I guess I'm not with the rest. I'd prefer ascii HEX format.
>> SIMH may not be around in 50 or 100 years.
> 50 years ago, ASCII (USASCII) wasn't terribly common, except on 7-level
> TTY.  A lot of machines used 6-bit codes and IBM's new line of S/360
> used EBCDIC.
> But I think I've run exactly one emulation on SIMH--IBM 1620--and it
> didn't involve tape.
Richard Swingwood has ported my Microdata 1600 emulation into simh, and 
every bit of software I have so far survives because of half inch 
tapes.  That which was on punched card source form was read to disk and 
is backed up on tape, so TAP is what we are using.  I also have a 
converter to go to AWS for mainframe Hercules stuff.

The Microdata M1621 Ascii is a weird ascii with the high order bit on in 
the character set, similar to EBCDIC, so the representation is 
important.  I think the OS you are on dictates that to some degree as 
far as sequencing the records as I did initially, but it is all moved to 
TAP once that is done.

No real concensus on metadata, though I think there was discussion about 
dumping it after the logical EOT, either two or three tape marks in the 
container, either TAP or AWS tape format.

> I chose the SIMH .TAP format because it was formally documented.  I
> include a copy of the document with every tape job.
> --Chuck

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