Unix v4 Tape Found

Significance of the Unix v4 tape

• Tape is from 1973; Unix v4 is described as “otherwise lost” and historically key as the first C-based version.
• Commenters see it as a big deal for Unix and OS history, even if code may be close to v5.
• There’s excitement about studying such early C, and pride from people connected to the institution where it was found.
• Some hope it will be uploaded to public archives like TUHS, archive.org, and Software Heritage.

Planned recovery technique

• Recovery plan: tap the tape head’s read amplifier, digitize the raw analog signal with a multi‑channel high‑speed ADC into ~100GB of RAM, then decode it in software (e.g., readtape).
• Motivation: tape might not survive multiple passes, so capture the fullest possible flux-level signal on the first try.
• Discussion of baking the tape (per “sticky-shed” practices) if needed; the person handling it hopes to avoid that because it’s slow.
• The tape is likely 9‑track, ~1000 ft, estimated 10–15 MB capacity—plausibly enough for sources, binaries, and docs.

Media longevity and preservation

• Several note that 1970s 3M 9‑track tapes can be quite resilient, especially if stored sealed and in a dry climate.
• Others warn that analog tapes (VHS, audio) are hitting serious degradation windows; VCR scarcity complicates rescue.
• Long subthread on optical media:
  • Pressed CDs may last decades; recordable CD‑R/DVD‑R can fail in a few years despite careful storage.
  • People report both flawless 10+ year archives and catastrophic failure of large DVD collections.
  • Discussion of disc rot, mold, foam off‑gassing in cases, and differing media quality.
  • Blu‑ray and “M‑disc” are cited as more durable, with heavy error correction.
• Modern best practice for magnetic media: treat it as analog, create flux‑level images, and interpret later (also used for floppies and even VHS via tools like vhs-decode).

Prospects for successful recovery

• Several commenters are cautiously optimistic:
  • 9‑track with parity bits gives decent resilience.
  • Utah’s dry climate and a sealed container are viewed as very good signs.
  • Even with some corruption, context (e.g., source code) could help reconstruct missing bits.
• Others note that tapes from that era “often haven’t held up,” so there is real risk.

Related historical and technical angles

• Interest in comparing v4 to already-available v5 sources.
• Curiosity about recovering the original B compiler; some background given on TMG and B’s history, with a link to at least one B implementation.
• Note that checksumming in Unix distributions only became common around v7, so v4 likely lacks built‑in integrity checks.

Off-topic but recurring themes

• Mastodon/Fediverse:
  • Some find it “cool” for decentralization and lack of engagement algorithms; others report toxic political content and UI annoyances (e.g., dark mode, preferences visibility).
  • Experiences differ widely depending on instance and personal filtering practices.
• A humorous bandwidth-of-a-station-wagon-style tangent:
  • Back‑of‑envelope calculations for shipping containers or cars full of micro‑SD cards; jokes about packing practicality, weight limits, AWS “Snowmobile,” and real-world “data by truck” stories.