[HECnet] Help to identify tap file format

[Dennis Boone]

I found several pdp-11 tape image files on the net which have ".tap"
suffix.   It isn't well known simh/e11/tap/tpc tape images.   Please help
to identify which format they have.   How such file can be converted to
simh .tap or .tpc or how it can be used/mounted?

It looks to me like some gomer "imaged" a tape with dd or similar tool,
possibly on a drive set to fixed 512-byte block size.   See, for example,
the 80 byte VOL1 record all alone in a 0x200-sized chunk with zero
padding.

If the original tape actually WAS fb512, and there was only one tape
"file" on the media, you might be able to convert this into an actual
.tap file by simply wrapping each chunk of 512 bytes in the proper
record length field.   That is, place a word 0x00000200 (note:
little-endian) before and after each 512 byte chunk of the input file,
and the words 0x00000000 and 0xffffffff at the end of the file.

If the tape wasn't fb512, or contains multiple logical files, then about
the only way to save the image would be to grovel through it trying to
intuit record boundaries based on intimate knowledge of the habits of
the tool used to write the original.

De