Technology Articles on Old Silicon

Bi-Color LED Daughter Card for ZuluSCSI

Fri, 24 Apr 2026 00:00:00 +0000

I modify my Sun workstations to feature a multicolor LED instead of the standard green LED that simply indicates power is on. After this modification, the LED on the front of the box lights up green when the power is on, but turns blue during drive access. I find this to be a useful addition, as it provides a clear visual indication of disk activity. Modern computers have conditioned us to expect immediate responses to commands or actions, but that’s not always the case with these older systems. This modification adds both functionality and a bit of visual interest.

Image Security and Checksums

Fri, 24 Apr 2026 00:00:00 +0000

I highly recommend downloading these images from oldsilicon.com and then checking the file checksum against what I provide alongside the images. Since these files might be loaded onto a classic machine that you’ve restored and that is connected to your network, there’s a risk that someone could alter the image after it’s downloaded, potentially creating an attack vector for your more modern computers. While I’m not doing this, I can’t vouch for others. If you share any of these images, please share the site link so others can read this advisory!

IRIX 6.5 Disk Image Notes

Fri, 24 Apr 2026 00:00:00 +0000

This README covers the IRIX 6.5 images I host on my site oldsilicon.com. I make these images available to help classic workstation enthusiasts get old hardware running more easily. Installing older OS versions can be time-consuming, so the goal of these prototype images is to simplify the process, allowing you to get started quickly and then customize as needed.

Below, you’ll find a checklist of tasks to get your machine up and running on your network. If you end up compiling useful tools and utilities not included in these images, please consider contributing them back to my project for inclusion in future versions.

Solaris 2.6 Disk Image Notes

Fri, 24 Apr 2026 00:00:00 +0000

This README covers the Solaris 2.6 images I host on my site oldsilicon.com. This text also appears in the README file in the root directory of the image.

I make these images available to help classic workstation enthusiasts get old hardware running more easily. Installing older OS versions can be time-consuming, so the goal of these prototype images is to simplify the process, allowing you to get started quickly and then customize as needed.

SunOS 4.1.4 (Solaris 1.1.2) Disk Image Notes

Fri, 24 Apr 2026 00:00:00 +0000

This README covers the Sun 4C prototype images I host on my site oldsilicon.com. It also appears in the root directory of the image.

Why is my Disk Image boot so slow?

Fri, 24 Apr 2026 00:00:00 +0000

A few things to consider.

First boot: network not yet configured

The first time you boot any of these disk images, the computer may not be correctly configured for your network. In this situation, the system will boot VERY slowly as various RPC calls fail. It can take up to 5 minutes for some of these systems to boot when they aren’t properly set up.

Be patient. Once the system finally finishes booting, follow the network setup steps listed in the README files to fix the network configuration. It may take a few reboots to get everything working correctly. Once properly configured, most of these machines will boot in 1 to 2 minutes.

ZuluSCSI Overview

Fri, 24 Apr 2026 00:00:00 +0000

ZuluSCSI is a solid-state direct replacement for a physical SCSI drive. Since it doesn’t rely on mechanical media, it’s an excellent choice for retro computers — no moving parts means silent, cool operation, and nothing that can fail the way a thirty-year-old disk can.

Performance

Based on my own informal benchmarking, I’ve found ZuluSCSI to be sufficiently fast for older computers. In side-by-side comparisons with real SCSI-2 hard disks, there’s little difference in real-world performance. The ZuluSCSI RP2040 supports read speeds up to 10 MB/s and write speeds up to 6 MB/s, which is well within the range of a period SCSI-2 controller.

cmacs: A Cross-Platform Terminal Editor for Vintage Unix

Sat, 18 Apr 2026 00:00:00 +0000

cmacs (cm) is a terminal-based text editor I wrote to solve a simple problem: I needed an editor that worked the same way on every machine in my collection. Not vi, not emacs, not nano—something that felt immediately familiar, stayed out of the way, and compiled cleanly on everything from a SPARCstation running SunOS 4.1.4 to a modern Mac.

The editor is available on GitHub and described in more detail on my project page.

Locked Out: Clearing the Firmware Password on Vintage Sun Workstations

Sat, 18 Apr 2026 00:00:00 +0000

If you have ever bought a used Sun workstation, or powered one up after years in storage, there is a good chance you have been greeted with a password prompt instead of the familiar ok prompt. The machine is convinced it has a firmware password set, and it will not let you into OpenBoot PROM without it.

The frustrating part is that the machine may never have had a firmware password. When the battery inside the timekeeper chip dies or its NVRAM contents become corrupt, the security configuration bytes can end up in a state that looks like a password has been set. The firmware dutifully enforces a password that nobody knows because it never existed.

Burning a New SPARCstation 1 PROM

Mon, 13 Apr 2026 00:00:00 +0000

I recently needed to burn a new OBP PROM for my SPARCstation 1. I’m always on the lookout for CG6 TGX+ SBus framebuffers for my SPARCstations and found someone selling a set of three for an unbelievably low price. These framebuffers are my favorite because they can drive LCD displays at 1280x1024, a more standard resolution than Sun’s native 1152x900.

But my SPARCstation 1 came with OBP version 1.0, which would not recognize the TGX+ card. After some research I determined that the last revision of OBP for the SPARCstation 1 was version 2.9. I have most of the Sun ROM images archived, so I checked and fortunately had that one.

Sun Boot ROM and Firmware Image Archive

Mon, 13 Apr 2026 00:00:00 +0000

Sun’s original firmware download site disappeared years ago when Oracle took over, and tracking down the right OBP update for a specific machine has become increasingly difficult. Over the years I’ve collected ROM images from various sources—archived FTP sites, the vintage Sun community, and other collectors. This page makes them available for download.

The collection spans Sun-3 boot ROMs through UltraSPARC system firmware, covering roughly 15 years of Sun hardware. The Sun-3 and early Sun-4/Sun4c images are raw PROM images that need to be burned to an EPROM chip using a programmer like the MiniPRO TL866II Plus. The Sun4u and later images are flash update packages designed to be applied from a running Solaris system.

Last OpenBoot PROM Versions for Sun Workstations

Fri, 10 Apr 2026 00:00:00 +0000

Every Sun workstation shipped with OpenBoot PROM firmware that handles hardware initialization, diagnostics, and the boot process. Sun released OBP updates over the life of each product to fix bugs, improve hardware compatibility, and add features. Knowing the last available version for your machine is important because OBP updates often resolved real problems: disk size limitations, SCSI quirks, multiprocessor stability, and Y2K issues among them.

Unfortunately, Sun’s original firmware download site is long gone. OBP update images can occasionally be found in archived collections and through the vintage Sun community, but tracking down the right file for your machine requires knowing what version you need.

Fixing a Corrupted TOD Clock on SunOS 4.1.4

Thu, 09 Apr 2026 00:00:00 +0000

If your SPARCstation won’t boot and all you see is “TOD clock not initialized” partway through the boot sequence, you may have corrupted the time-of-day chip by attempting to set a modern date under SunOS 4.1.4. This article explains how that happens and how to fix it using a Solaris 2.6 install disc.

Background

After replacing a dead timekeeper chip and reprogramming the IDPROM, your SPARCstation should boot normally. If you are unfamiliar with those procedures, see M48T02 Timekeeper External Battery Mod for the hardware repair and Resetting IDPROM on Sun Workstations for programming the machine type and Ethernet address.

CDE Keyboard Repeat Rate on Solaris 2.6

Mon, 06 Apr 2026 00:00:00 +0000

If you’ve used CDE on Solaris 2.6 for any length of time, you’ve probably noticed that the default keyboard repeat rate feels sluggish. The default autorepeat delay is 500 milliseconds before a held key begins repeating, and once it starts, keys repeat every 50 milliseconds. For anyone accustomed to a faster repeat rate, this can make editing text or navigating the terminal feel painfully slow.

CDE’s Style Manager provides a toggle to enable or disable autorepeat entirely, but it does not expose the actual repeat rate or delay settings. To change those, you need to pass options directly to the X server.

Compile Time Comparisons Across Vintage and Modern Hardware

Mon, 06 Apr 2026 00:00:00 +0000

One of the things I enjoy doing when I get a vintage machine running is putting it through a real-world workload. Synthetic benchmarks are fine, but nothing tells you how a machine feels quite like watching it do actual work. For this test, I compiled a set of C++ libraries I wrote over the course of my career, roughly 33,000 lines of code, on every machine in my collection that could handle it.

DOS Networking with mTCP

Mon, 06 Apr 2026 00:00:00 +0000

Getting a vintage DOS machine connected to a modern network might seem impossible, but thanks to the work of Mike Brutman and others in the retro computing community, it’s not only possible but surprisingly practical. The key is a combination of packet drivers and mTCP, a lightweight TCP/IP stack designed specifically for DOS.

The Challenge of DOS Networking

In the DOS world, TCP/IP was an afterthought. Network cards existed in the mid-80s, but they were expensive and primarily used for proprietary networking protocols like Novell NetWare. DOS was never designed for networking—it’s not multitasking, it has no built-in network stack, and it has limited memory to work with.

Getting SunOS 4.1.4 Working

Mon, 06 Apr 2026 00:00:00 +0000

Getting SunOS 4.1.4 installed and fully functional on real hardware turned out to be more difficult than I expected. What should have been a straightforward install from CD turned into a series of false starts, mostly around disk partitioning and disk labels. After several failed attempts I found it was far easier to start with a disk that already had a valid Sun disk label on it rather than trying to get the installer to label a blank drive correctly.

Replacing a Sun IPX Power Supply with a Mini ATX

Mon, 06 Apr 2026 00:00:00 +0000

The power supply is always the first thing to go on vintage Sun workstations. The original supplies in the SPARCstation IPC, IPX, and LX are proprietary units that are increasingly difficult to find and expensive when they do turn up. When the power supply in my SPARCstation IPX failed, I replaced it with a TF Skywindintl TF400, a compact 1U Mini ATX supply rated at 350 watts. It is inexpensive, readily available, and vastly overpowered for the IPX, which makes for a reliable replacement.

M48T02 Timekeeper External Battery Mod

Thu, 15 Aug 2024 00:00:00 +0000

The M48T02 timekeeper chip is found in many vintage computers from the late 1980s and early 1990s, including Sun SPARCstations, SGI workstations, and various other systems. These chips combine a real-time clock, NVRAM, and a lithium battery in a single package. The problem is that the battery is sealed inside the chip and eventually dies, taking the clock and stored settings with it.

You can buy replacement M48T02 chips, but they’re becoming harder to find and increasingly expensive. Worse, any new chip you install will eventually suffer the same fate. A better solution is to modify the existing chip to use an external coin cell battery that can be easily replaced.

ZuluSCSI Disk Images

Mon, 12 Aug 2024 00:00:00 +0000

I’ve made bootable disk images available for most of the workstations in my collection. Almost all the workstations use ZuluSCSI SCSI emulators for their primary disk, making it easy to back them up and mount CD images without actually dragging a CD-ROM drive out.

These images are available free for anyone pursuing getting a classic workstation functional again. You can find the download link for each image on the corresponding workstation or pizza box article page.

The Rise and Fall of SPARCstation Clones

Thu, 04 Apr 2024 00:00:00 +0000

In the early 1990s, Sun Microsystems made a bold decision that shaped the workstation market: it opened up the SPARC architecture for licensing. The result was a short-lived but fascinating ecosystem of third-party workstation manufacturers producing machines that were functionally identical to Sun’s own hardware — often at a fraction of the price.

The Open Architecture Gambit

Sun authorized chipmakers like Fujitsu Microelectronics, LSI Logic, and Tera Microsystems to resell its 40 MHz SPARC logic chipset and the SPARCstation 2 board design. These licensees could then supply SPARC-compatible system vendors, opening the floodgates for clones. The SPARCstation 2, with its CY7C601 processor running at 40 MHz and delivering roughly 28.5 MIPS, became one of the most widely cloned designs.

Commodore 64 Hardware Reference

Mon, 15 Jan 2024 00:00:00 +0000

For anyone working on Commodore 64 hardware, Ray Carlsen’s website is the absolute bible for technical documentation.

Ray Carlsen’s Commodore Reference

Ray Carlsen maintains an authoritative Commodore 64 hardware resource with detailed technical documentation covering:

Power supply repairs and replacements
Common failure modes and diagnostics
Component-level repair guides
Schematics and technical specifications

This is an essential bookmark for anyone serious about Commodore restoration.

Resource: https://www.portcommodore.com/rcarlsen/

Commodore SX-64 Schematics

Mon, 15 Jan 2024 00:00:00 +0000

The Commodore SX-64 was the first full-color portable computer, released in 1984. It was essentially a Commodore 64 built into a portable case with a 5-inch color CRT monitor and a built-in 1541 floppy disk drive.

These schematics are invaluable for repair and restoration work on the SX-64.

Download

Download SX-64 Schematics (ZIP, 20MB)

Compaq Portable BIOS Diskettes

Mon, 15 Jan 2024 00:00:00 +0000

Compaq computers of the Portable II and Portable III era did not have BIOS modification screens built into ROM as became the standard in the industry. With most machines, you can hold some combination of keys on the keyboard while the machine is booting up and get to a configuration screen before DOS loads. Compaq machines, however, use a different strategy.

The only way to change BIOS variables on these machines is to boot the Compaq Diagnostics Diskette, which then provides the user interface to make changes to the BIOS. If you don’t have that diskette, you aren’t going to be successful with a Compaq Portable II or Portable III.

IBM PCjr Resources

Mon, 15 Jan 2024 00:00:00 +0000

The IBM PCjr has a dedicated community of enthusiasts who have created invaluable resources for restoration and upgrades.

Mike Brutman’s PCjr Page

Mike Brutman’s comprehensive PCjr resource is the absolute authority on all things PCjr. The site features active community forums and detailed technical content covering everything from basic setup to advanced modifications.

Resource: https://www.brutman.com/PCjr/pcjr.html

TexElec

TexElec manufactures specialized boards for the PCjr including the JRIDE (Jr IDE Board), which allows you to add IDE storage to your PCjr. The owner is responsive and proactive with customer support.

Indy Retro-Reimagined Display

Mon, 15 Jan 2024 00:00:00 +0000

This project documents the transformation of a Sun LCD monitor into a retro-styled display matching the iconic teal aesthetic of Silicon Graphics Indy workstations from the 1990s. The original Indy shipped with Silicon Graphics’ own CRT monitors, but those are increasingly difficult to source in working condition, and they draw a meaningful amount of power from a machine I actually want to use day-to-day. The idea here is simple: take a reliable, period-adjacent LCD and dress it in Indy clothing.

NeXT Retro-Reimagined Display

Mon, 15 Jan 2024 00:00:00 +0000

This project describes the transformation of a Sun LCD monitor into a retro-styled NeXT display that never actually existed in the original NeXT product line.

The Problem

When restoring a NeXTstation Color, finding an appropriate period display can be challenging. Original NeXT monitors are rare and expensive. Using a modern LCD works functionally but detracts from the vintage computing experience. Even pairing it with an authentic Sun monitor didn’t quite feel right for showcasing the NeXTstation.

Resetting IDPROM on Sun Workstations

Mon, 15 Jan 2024 00:00:00 +0000

This guide provides instructions for reprogramming the IDPROM (Identification PROM) on various Sun workstation models, including sun4c, sun4m, sun4d, and sun4u architectures.

The IDPROM contains critical system identification information including the machine type, Ethernet MAC address, and serial number. When the NVRAM battery dies (which happens on all Sun workstations eventually), this information is lost and must be reprogrammed.

Prerequisites

Before attempting IDPROM modification, document your existing IDPROM data if possible:

Silicon Graphics Parts Sources

Mon, 15 Jan 2024 00:00:00 +0000

Finding parts for Silicon Graphics workstations can be challenging. These vendors specialize in vintage SGI equipment.

Ira Moser

Ira Moser maintains a collection of vintage SGI equipment salvaged from defense contractors. Direct contact is recommended for specialty items that may not be listed.

Resource: http://www.meco.org/catalog/

SGI Depot

SGI Depot offers comprehensive inventory listings and is a good resource for specialized equipment searches.

Resource: http://www.sgidepot.co.uk/sgidepot/vw.html

Sun Hardware Reference Guide

Mon, 15 Jan 2024 00:00:00 +0000

This comprehensive reference guide covers Sun workstation hardware specifications and technical details.

Sun Hardware Reference

The Sun FAQ and hardware reference provides detailed information about Sun workstation models, specifications, and technical documentation.

Resource: http://www.alyon.org/InfosTechniques/informatique/SunHardwareReference/sunfaq.html

SunOS 4.1 Using DNS without NIS

Mon, 15 Jan 2024 00:00:00 +0000

This document describes modifying the shared C library on SunOS 4.1.x systems to use DNS resolution via /etc/resolv.conf instead of NIS-based hostname lookups.

Prerequisites

Superuser access required
“SHLIB CUSTOM” package installed via SunInstall or add_services
Properly configured /etc/resolv.conf file
Ability to verify with /usr/etc/nslookup

Step-by-Step Procedure

1. Create Working Directory

cd /usr/lib/shlib.etc
mkdir tmp
cd tmp

2. Extract Library Objects

Extract position-independent code objects and remove symbol definitions:

ar x ../libc_pic.a
rm __.SYMDEF
mv rpc_dtablesize. rpc_dtablesize.o
mv rpc_commondata. rpc_commondata.o
mv xccs.multibyte. xccs.multibyte.o
ar x /usr/lib/libresolv.a

The resolver library objects are already position-independent and can be merged safely.

Bootable Compact Flash Card for IBM PCjr

Sat, 19 Nov 2022 00:00:00 +0000

This guide documents the process of creating a bootable compact flash card for the IBM PCjr. Using a CF card as a hard drive replacement provides reliable, silent storage for your vintage PCjr.

Requirements

40-pin IDE to Compact Flash adapter (not 44-pin!)
Compact Flash card (I used a 15GB SanDisk II)
DOS 3.3 boot floppy disks
Power connection for the adapter

Important: Make sure you get a 40-pin IDE adapter, not a 44-pin. Lesson learned the hard way. These are available on eBay for around $6.

Retrobright: Science and Philosophy

Sun, 16 Oct 2022 00:00:00 +0000

Retrobright is a technique for bleaching old, yellowed plastic back to its original or near-original color. The yellowing that affects vintage computer plastics occurs due to a chemical reaction in ABS plastic when exposed to heat and ultraviolet light over time.

For those interested in the detailed chemistry behind this deterioration, the Hackaday article “The Retrobright Mystery” provides an excellent technical explanation.

Most Affected Systems

Certain computer models suffer particularly badly from discoloration. Apple IIs, Osbornes, and Ataris are among the worst, often turning a horrible yellow color that bears little resemblance to their original appearance.