# simh/simh

The Computer History Simulation Project

Repository: https://github.com/simh/simh
Canonical: https://ross.abutalabs.com/products/simh
Homepage: http://simh.trailing-edge.com
Language: C
License: NOASSERTION
License Family: other
Last push: 2026-08-12T02:14:37+00:00

## Health v2 (maintenance only)
Score: 66/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 97, release rhythm 8, longevity 100
- inputs: {"age_days": 5615, "days_push": 22, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: no_license
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1877, forks 315 (observed 2026-08-28T04:05:47.856120+00:00)

## What it is
SIMH is a collection of highly portable simulators for historically significant computer systems such as the DEC PDP series, VAX, IBM mainframes, and Altair 8800. It lets users run vintage operating systems and software on modern hardware, preserving computing history.

## Use cases
- run old VAX or PDP-11 operating systems on a modern PC
- emulate vintage computers like the PDP-8 or IBM 1401
- preserve and study historic computer software
- boot retro operating systems for learning or nostalgia
- test legacy software without original hardware
- explore the history of computing through working simulations

## When to choose
- you need to run or preserve software for emulated historic hardware
- you want a portable, scriptable multi-system simulator in C
- you're researching vintage operating systems or computer architecture

## When to avoid
- you need emulation of modern hardware or gaming consoles
- you want a GUI-first emulator with plug-and-play disk images
- you need cycle-accurate hardware-level emulation for restoration work

## Facets
- artifact type: application
- maturity: active
- function: simulation, interpreter, developer-tools
- domain: simulation, operating-systems, hardware, developer-tools, education
- platform: windows, cross-platform, cli
- tags: emulator, retro-computing, pdp-11, vax, computer-history, legacy-systems, linux, macos

## Member repositories
- simh/simh (main) score 66

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:05:47.856120+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T03:14:43.240966+00:00, confidence not recorded.
  - readme: https://github.com/simh/simh (fetched 2026-08-28T04:05:47.856120+00:00, sha 4929e1a8b5a4)
  - homepage: http://simh.trailing-edge.com (fetched 2026-08-29T10:53:30.375849+00:00, sha dd9f93df9788)
  - site_page: http://simh.trailing-edge.com/pdf/all_docs.html (fetched 2026-08-29T10:53:30.385313+00:00, sha a90756f784fc)
- Data as of 2026-08-30T08:39:29.467469+00:00.