Retrocomputing on csegura

Changing the SGI Octane’s Light-Bar LEDs

Sun, 25 Oct 2026 00:00:00 +0000

A small change to an SGI workstation

I changed the indicator LEDs in my SGI Octane’s light bar. I chose blue LEDs and added two resistors to keep their current within a safe range.

The light bar is a narrow assembly in the front of the case. Its lights make the computer’s status visible from the outside. I wanted to replace the dead lights and give them a blue glow.

NorthStar Advantage Restoration Part 1

Sun, 25 Oct 2026 00:00:00 +0000

A restoration that took more than a year

I bought this NorthStar Advantage on Wallapop in 2024. The seller told me that the keyboard had a fault. But at power-on, the computer still displayed a message on the screen. As always trust in the seller’s words, was an act of faith.

Indeed, buying vintage computers is always a bit of a gamble but be prepared for surprises when dealing with vintage hardware.

NorthStar Advantage Restoration Part 2

Sun, 25 Oct 2026 00:00:00 +0000

Looking more closely at the drives

This continues NorthStar Advantage Restoration Part 1, with a closer look at the drive hardware and how floppy disks mark sectors.

Many computers from the late 1970s and early 1980s used 5¼-inch floppy drives. The Tandon TM100-2A is one example. These drives can become difficult to use as they age. Their radial alignment—the position of the read/write head across the disk’s tracks—can shift. If it moves far enough, the drive may not read or write disks reliably.

NorthStar Advantage Restoration Part 3

Sun, 25 Oct 2026 00:00:00 +0000

This continues NorthStar Advantage Restoration Part 2. This time, I focus on replacing the keyboard’s foam pads.

I had to wait three months for the replacement foam-and-foil pads to arrive. The first package was lost in transit, so I had to reorder them, which added to the delay.

Once they were in hand, I could proceed with the restoration work on the keyboard.

The replacement pads

There are not many places that sell these specific foam-and-foil pads, so finding a reliable source is important.

NorthStar Advantage Restoration Part 4

Sun, 25 Oct 2026 00:00:00 +0000

This continues NorthStar Advantage Restoration Part 3. This time, I am making 5¼-inch drive cases and fitting Gotek replacements.

Making a case for the drive bays

The NorthStar Advantage has two drive bays, and I want to use them with a Gotek floppy-drive emulator. A Gotek is a device that can stand in for a floppy disk drive. It uses a USB flash drive to provide disk images instead of physical floppy disks using a USB stick.

Qume Terminal

Sat, 28 Mar 2026 00:00:00 +0000

Bringing a QVT terminal to life on Linux over USB serial

Vintage serial terminals are simple when everything matches, and maddening when one setting is off by a single bit.

Recently, I got a Qume QVT-119 Plus terminal working as a serial console on Linux. The terminal is connected to a Raspberry Pi via a USB-to-serial adapter, and the Pi is running agetty to present a login prompt on the terminal.

IRIX Services

Sat, 21 Jun 2025 00:00:00 +0000

Recently the hard disk of my SGI O2 has failed, and I have been trying to recover the data from it. A long history of trying to recover the data, but finally I have been able to recover it. In the next days I have to explain how to use reanimatot to do a fresh install of IRIX.

Today I’m triying to recompile Vim 8.1 as I had before. While the system is working, I’m using telnet to connect to the O2 and run the commands. I want to enable SSH so I have been exploring the system services.

SGI Reanimator

Sun, 08 Jun 2025 00:00:00 +0000

SGI reanimator is a tool for restoring and managing SGI IRIX systems. It provides all necessary tools to install IRIX. (bootp, tftd end the CD images, yeras ago I did it tio install linux on a sun sparcstation ultra and it was a pain to get it working, so this is a great tool)

SGI Reanimator

# hinv
Autoload=Yes
console=g
diskless=0
dbaud=9600
volume=80
sgilogo=y
autopower=n
monitor=h
netaddr=192.168.1.105
eaddr=08:00:69:0b:83:e1 
boottune=1
ConsoleOut=video
ConsoleIn=keyboard
SystemPartition=xio(0)pci(15)scsi(0)disk(1)rdisk(0)partition(8)
OSLoadPartition=xio(0)pci(15)scsi(0)disk(1)rdisk(0)partition(0)
OSLoadFilename=/unix 
OSLoader=sash
gfx=alive
Kernname=ide

I’ve modified my reanimator config to use the following settings to use it from my home network:

BBC Disk field notes

Sat, 03 May 2025 00:00:00 +0000

I recentrly bought a broken BBC Diskdrive and a Watford DFS disk controller card, to try to repair it. The disk drive is a dual 5.25" disk drive, and the controller card is a Watford Electronics DFS (Dual Disk Filing System) card version 1.54T.

The unit comes with two different disk drives, a Mitsubishi MF503A and a Mitsubishi M4853-342MG. Each drive has a switch on the front panel to select between single-density (40 tracks) and double-density (80 tracks) operation.

Replacing the 5.25" Disk Drive

Sat, 29 Mar 2025 00:00:00 +0000

Replacing the 5.25" Disk Drive

I have a 5.25" disk drive that is not working properly. I have tried to clean the heads, but it is still not working. I have decided to replace it with a new one. I have found a new 5.25" disk drive on Wallapop (like ebay here in Spain), and I have bought it. Most of units are used, and untested, so I have been careful selecting the one I want to buy. Seller says that the disk drive is untested but was retired working. It’s no the first time I buy untested hardware, so the seller seems quite honest, and I trusted her.

Installing an SD Card Interface on the Apple IIc

Sat, 01 Feb 2025 00:00:00 +0000

Installing an SD Card Interface on the Apple IIc

Finally I got the SP ][ SD interface for the Apple IIc. This interface allows you to connect an SD card to the Apple IIc and use it as a mass storage device. The installation is quite simple, and the results are amazing.

It use an arduino nano to manage the SD card and the communication with the Apple IIc. The interface is connected to the disk II port of the Apple IIc, and it is powered by the Apple IIc itself. Great design!

C128 VICII video replacement

Tue, 21 Jan 2025 00:00:00 +0000

C128 VIC video replacement

After spent a lot of hours trying to fix the video signal on my C128, checking signals, replacing capacitors, replacing the RF modulator with the TSH7316 module etc.. and with the cues that each try gave me, I’ve decided to replace the VIC-II chip. The VIC-II chip is the video controller chip used in the C128.

Documentation

The main problem was that the video signal was faded, dull, it was dificult to see the letters on the screen and in C64 mode the screen was almost impossible to read.

Z80 v2

Sun, 05 Jan 2025 00:00:00 +0000

Z80 v2

I’m not sure but still soon to say that this year will be the year of the Z80. I’ve been working on a new version of the Z80 computer that I’ve built last year. The new version that I have in mind will have a lot of improvements over the previous one, and possibly a printed circuit board (PCB) to make it more professional.

Improvements that I have in mind:

SparcStation Afternoon

Sat, 28 Dec 2024 00:00:00 +0000

Some pictures about second attempt to install T2/Sde 24.12 on my Sun SparcStation 5.

And the final result, the system crashed during the installation, with the whatchdog timer error.

A Technical Overview of the Sun SPARCstation 5

The Sun SPARCstation 5 (commonly referred to as the SS5) is a workstation computer introduced by Sun Microsystems in 1994. It was part of Sun’s highly successful SPARCstation family, which became renowned for their use in engineering, scientific computing, and other technical fields. The SS5 was built around Sun’s proprietary SPARC architecture and remains a notable example of 1990s workstation technology.

Windows 1 Installation

Wed, 25 Dec 2024 00:00:00 +0000

Installing Windows 1.0 on an Already Installed MS-DOS 3.3 System

Introduction

Microsoft Windows 1.0, first released in 1985, was a significant step in personal computing, heralding the shift from command-line interfaces to graphical user interfaces (GUIs). Even though it was rudimentary by today’s standards, it laid the groundwork for the Windows operating environment that countless systems rely on today. For enthusiasts and tech aficionados, installing Windows 1.0 over an already installed MS-DOS 3.3 system presents a time capsule that exemplifies the early days of modern computing. This guide explores the history, features, and steps needed to embark on this nostalgic installation journey.

C128 fixing video signal

Sat, 30 Nov 2024 00:00:00 +0000

Revamping the Commodore 128 Video Output: Removing the RF Modulator for Enhanced RGBI Output

Today I’ve decided try to fix the video signal on my C128. The video signal was not as bright as it should be.

The Commodore 128 (C128) is a vintage computer that has carved its niche in the hearts of retro computing enthusiasts. When it comes to video output, many users have wrestled with the limitations and quality of the original RF (radio frequency) modulator. This article delves into the process of removing the RF modulator and replacing it with a high-quality RGBI output using the TSH7316 IC, a specialized HDTV video amplifier. Leveraging RGBI not only enhances the video quality significantly but also makes connectivity with modern displays much easier.

C128 fixing video signal

Sat, 30 Nov 2024 00:00:00 +0000

C128 fixing video signal

Today I’ve decided try to fix the video signal on my C128. The video signal was not as bright as it should be.

I’ve decided to remove the RF modulator and use the RGBI output and replace it with a new one based on TSH7316 IC.

Documentation

The module

After replacing the RF modulator with the TSH7316, the video signal is the same, so the problem is not the RF modulator :-). I will continue investigating the issue. Maybe the problem is in the MOS8701 chip or the VIC-II chip.

Os2/warp3 installation

Sat, 30 Nov 2024 00:00:00 +0000

Some screenshots of the OS2/Warp3 installation process.

Cleaning Avid Ultra 320/LVD SCSI Drives

Sun, 22 Sep 2024 00:00:00 +0000

Cleaning Avid Ultra 320/LVD SCSI Drives

I recently acquired a couple of Avid Ultra 320/LVD SCSI drives. These drives are used in the Avid DS Nitris system, which is a high-end video editing system. The drives are:

2 x 146GB Seagate Cheetah 15K.5 drives.
2 x 300GB IBM Ultrastar 10K300 drives.

The drives are in good condition, but they have been sitting in storage for a while. I decided to clean them before using them.

Trying T2sde Linux on a Sun Sparcstation 5

Sat, 21 Sep 2024 00:00:00 +0000

Trying T2sde Linux on a Sun Sparcstation 5

I have a Sun Sparcstation 5, it has installed NetBSD 9, that was the nearest OS that I could install on it. I wanted to try Linux on it, years ago I was able to install linux on a Ultra 1, from the network using a TFTP server and the process was fun. I learned a lot.

Recently I had read about T2sde, a distribution that supports a lot of architectures, including SPARC. I decided to give it a try. There a lot of packages available, and the process sounds easy, and the best the have one of the most recent versions of the Linux kernel. Amazing!

Fixing Sharp MZ-700

Fri, 23 Aug 2024 00:00:00 +0000

Fixing Sharp MZ-700

Time to fix the Sharp MZ-700, I have this computer for a while, and it was not working. I decided to fix it. I opened the computer and I found that the power supply was not working correctly. I decided to do the standard procedure, replaced suspects capacitors and voltage regulators. Here are some pictures of the process:

This machine was manufactured in 1982, and it was a very popular computer in Japan. It was used in schools and homes. It has a Z80 CPU, 16KB of RAM, and 16KB of ROM. It has a built-in tape recorder, and it can display 40x24 characters in 8 colors.

C128 RGB Video 80col

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

C128 RGB Video 80col cable

The C128 seems to be lossing the brightness signal in the Composite output, the video is fine but the colors are not as bright as they should be.

I’ve decided finally do the cable to connect the C128 rgbi output using composite video. The cable is a simple DB9 pin to phono RCA cable, ground to pin 1 and video signal to pin 7.

mtcp tools

Sun, 14 Jul 2024 00:00:00 +0000

ftp_server / telnet_server

Warning

These tools are quick-and-dirty solutions, not meant for serious or long-term use. It also serves as a subtle reminder that they should be used cautiously due to their lack of security features :-)

I wanted to have two fast programs to communicate with my old computers, from my linux box, I have three old pcs and I’m using mtcp on them. mTcp includes an ftp client and a telnet client, of course, I could use any of the existing ftp servers or telnet ones, but I don´t want to have more services running, also I thought that would be an opportunity to learn something.

CPM Disk Tool

Sat, 22 Jun 2024 00:00:00 +0000

CPM Disk Tool

I’m currently working on implementing a CP/M for my small Z80 CPU. As a reminder, this involves a single Z80 CPU connected to a Raspberry Pi, with the latter emulating RAM, ROM, and IO devices.

I spent this weekend diving into the workings of CP/M disks. While there is a Unix tool available to create CP/M disk images , I’ve decided to create my own version using Python.

ISA-PicoMem

Wed, 05 Jun 2024 00:00:00 +0000

I’m restoring this wonderful IBM XT 5150, machine powered up, but there wasn’t os. Floppy drive was`t working, I tried to boot from a 720k floppy disk, but it was impossible. So looking for a solution, I found a ISA-PicoMem (https://github.com/FreddyVRetro/ISA-PicoMEM/tree/main) card, a wonderful card that allows you to boot from a SD card, add memory, and is able to connect to a network using wifi and ne2000 drivers, of course you need install mTCP.

Connecting a Z80 to a Raspberry Pi

Mon, 18 Mar 2024 00:00:00 +0000

I have a long history with computers, starting with a Sinclair Zx81 that I still own, followed by other models and others that I wished for, as time went by.

A while back, I found an old box with some old processors, x386, x486, a few Pentiums first generation and two Zilog Z80. Then I got a kind of retro-feeling in my mind and I watched some YouTube videos about them. One of them was the classic nop-test, I had fun with this for a whole afternoon.

Fixing Dragon 32 Power supply

Sat, 16 Mar 2024 00:00:00 +0000

This morning the Dragon 32 power supply broke. I have a Dragon 32 that I bought one time ago. But when I tried to turn it on, it didn’t work. I checked the power circuit inside of the Dragon 32 and found that the regulator was broken.

It was a LM340T 7812, 12v regulator, so I replaced it with a new one. But when I tried to turn it on, it didn’t work.

IBM 5150 Motherboard

Sat, 03 Feb 2024 06:37:07 +0100

I have been repairing the IBM 5150 motherboard.

Tantalum Capacitors are known to fail, :-) This is the famous C56

Almost each memory chip had a tantalum capacitor.

Also ISA slots had tantalum capacitors.

This ones, near the power supply connector, were also tested.

IBM Model M keyboard

Sat, 03 Feb 2024 06:37:07 +0100

I have been repairing the model m keyboard, but not lucky this time. The membrane is broken and I have to replace it. I have to find a replacement membrane.

Fixing the Dragon 32

Sun, 14 Jan 2024 07:07:07 +0100

I have been repairing the Dragon 32

When I powered it up, the screen was all garbled. I opened it up and found a capacitor that was bulging.

Nude Dragon

Replaced Capacitor

First attempt to fix it was to replace the bulging capacitor. I replaced it with a new one, but after powering it up, the cursor was missing.

Finally I have had to replace most of the capacitors on the board.

LLM Conversation Commodore 64 vs ZX Spectrum

Wed, 11 Oct 2023 07:07:07 +0100

Playing with langchain this is the conversation between a Commodore 64 and a ZX Spectrum.

Debate rules

You are in a debate your goal is to persuade your conversation partner of your point of view. 
Argue about topic polite. Be concise and conclusive use arround 60 words.
DO look up information with your tool to refute your partner's claims.
DO NOT fabricate fake citations.
DO NOT cite any source that you did not look up.
Do not add anything else.
Stop speaking the moment you finish speaking from your perspective.
Context: {memory}

Conversation for 10 rounds