Abstract:

This document is a highly detailed technical guide and personal memoir from 1996, titled "This Old SGI," dedicated to the ownership, repair, and modification of vintage Silicon Graphics (SGI) 4D series workstations. It serves as a hardware hacker's reference for the Professional IRIS (4D/50-85), Personal IRIS (4D/20-35), and Power Series (4D/xxx) machines, covering everything from IRIX installation, PROM monitor commands, and hardware specifications to intricate hacks like clock speed-ups and converting Sun peripherals for SGI use.

A modern Hacker News discussion accompanies the guide, reflecting on SGI's legacy. Commenters share nostalgic anecdotes about the power and elegance of the IRIX operating system and the unique SGI user experience. The discussion also contextualizes SGI's decline, attributing it to the rise of affordable, scalable consumer 3D graphics from companies like Nvidia and 3dfx, and highlighting how modern low-cost hardware like the Raspberry Pi has vastly surpassed the performance of these once-legendary workstations.

This Old SGI: A Deep Dive into Vintage Workstation Hacking and Legacy

• A Comprehensive Hacker's Guide: The core document is a 1996-era guide for hobbyists looking to revive and maintain obsolete SGI 4D series machines. It provides detailed information on hardware configurations, performance, IRIX OS installation, and troubleshooting.

• IRIX OS and Booting: The guide details the practical steps for getting a system running, including:

  • Choosing the right IRIX version (e.g., 4.0.5 for memory-constrained systems).
  • Booting from a CDROM on systems with older PROMs that don't natively support it.
  • Gaining root access and resetting passwords.
  • Understanding the unique IRIX boot disk anatomy, including the volume header partition (volhdr) and the standalone shell (sash).

• Low-Level System Control: Extensive documentation is provided for the PROM monitor, the system's pre-boot command interface. This includes a full list of commands for diagnostics, booting, and managing environment variables stored in NVRAM. It also identifies the common failure point of the Dallas SmartWatch chip, which contains the battery-backed RTC and NVRAM.

• Hardware Specifications and Upgrades: The guide meticulously documents the various machine series:

  • Professional & Power Series (4D/50-85, 4D/xxx): These tower systems are characterized by their VME bus architecture, multi-card graphics subsystems (GT, GTX, VGX), heavy power requirements (often a 20-amp circuit), and a largely undocumented Philips SAA1099 audio chip.
  • Personal IRIS (4D/20-35): These more compact desktop systems feature a modular "E-module" design, varied memory types (from standard 30-pin to proprietary 64-pin SIMMs), and unique serial ports with Macintosh peripheral compatibility.

• Unique Hardware Hacks and Modifications: True to its "hacker" nature, the document provides instructions for various non-standard modifications, including:

  • Converting an old Sun-3 optical mouse to work on an SGI system.
  • Experimenting with "hot-clocking" CPUs for better performance.
  • Defeating the NVRAM password on later models.
  • Discovering and accessing hidden diagnostic monitors, such as the 68020-based monitor on the GM1 graphics card.

• The SGI Legacy and User Experience (Hacker News Discussion): Users reflect on why SGI systems were so special:

  • The IRIX operating system was considered far ahead of its time, with advanced features like the XFS journaling filesystem, a highly integrated graphical user interface (Indigo Magic Desktop), and robust network transparency.
  • Anecdotes describe using networks of SGI machines for complex tasks like VFX rendering, highlighting a level of power and flexibility that was unparalleled in the 90s.

• The Rise of Consumer 3D: The discussion contextualizes SGI's eventual decline. While SGI focused on expensive, bespoke, multi-board graphics solutions, former SGI engineers founded companies like 3dfx that, along with Nvidia, pioneered a scalable, single-chip approach. This consumer-focused model ultimately out-competed SGI's high-end professional one.

• Moore's Law in Action: Commenters point out the dramatic progress in computing power. A modern, inexpensive single-board computer like the Raspberry Pi offers significantly more processing power (measured in GFLOPS) than a top-of-the-line SGI workstation from the mid-90s, which originally cost tens of thousands of dollars.