It's more like a very slow floppy drive than like a tape. You may have DECtape-I (tu56) or DECtape-II (tu58). If it's DECTape-II, https://retrocmp.com/tools/tu58fs is probably what you want; it doesn't do great for VAX 11/730 booting, but it should be OK for file extraction. SIMH has reasonable support for both -I and -II devices but you may have to pull the code out and make your own tool--I don't know of a tu58fs equivalent for tu56.

Adam

On Tue, May 27, 2025 at 10:18 AM Thalia Archibald via TUHS <tuhs@tuhs.org> wrote:

Yufeng Gao wrote:
> The s1 tape is a UNIX INIT DECtape containing the kernel, while s2 includes
> most of the distribution files.
[https://www.tuhs.org/pipermail/tuhs/2025-February/031420.html]

Hello Yufeng,

Do you have more details on the format of the s1 tape? I want to reproduce your
work.

The s2 tape is in the tap format, which was easy to decode, and I assumed that
s1 was similar, just with its file headers on an earlier tape. I’ve been able to
fairly accurately segment s1 into files by observing that blocks duplicate the
tail of the previous block when they are not a full 512 bytes. I’ve written a
tool for this and have segmented all the text files and some of the binaries,
but I’m floundering on the rest. What you say seems to suggest that s1 actually
does have file metadata.

Thalia