A Cycle-Accurate Intel 8088 Core For All Your Retro PC Needs

December 3, 2022 by Jenny List 17 Comments

A problem faced increasingly by retrocomputer enthusiasts everywhere is the supply of chips. Once a piece of silicon goes out of production its demand can be supplied for a time by old stock and second hand parts, but as they become rare so the cost of what can be dubious parts accelerates out of reach. Happily for CPUs at least, there’s a ray of hope in the form of FPGA-based cores which can replace the real thing, and for early PC owners there’s a new one from [Ted Fried]. MCL86 is a cycle accurate Intel 8088 FPGA Core that can be used within an FPGA design or as a standalone in-circuit replacement for a real 8088. It even has a full-speed mode that sacrifices cycle accuracy and can accelerate those 8088 instructions by 400%.

Reading the posts on his blog, it’s clear that this is a capable design, and it’s even been extended with a mode that adds cache RAM to mirror the system memory at the processor’s speed. You can find all the code in a GitHub repository should you be curious enough to investigate for yourself. We’ve pondered in the past where the x86 single board computers are, perhaps it could be projects like this that provide some of them.

Stack Trace From The 1950s Punches Again

December 2, 2022 by Chris Lott 5 Comments

This repair/tutorial video by the telephone Connections Museum of Seattle features an amazing piece of electro-mechanical technology from the 1950s — the 5XB trouble recorder. Museum volunteer Sarah the “Switch Witch” has a deep passion for old phone equipment, and gives an excellent description of the trouble recorder, the problems it solved, and how it works, and how they went about fixing it.

As central office switching became more complex and more dense, the manual methods of hunting down faults became unmanageable. Semi-automatic approaches using trouble lamps, but even that had its limits. This “stack trace”, which could have hundreds of indicators, had to be frozen while the technician recorded the status on a form. If another fault came along during this time, it was lost. The solution, using the available technology of the day, was a mind-boggling punched card apparatus that punches over a thousand bits of information when an switching error is detected or when various watchdog timers expire.

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A Handy Guide To The Humble BBS

November 29, 2022 by Bryan Cockfield 37 Comments

Some of us who’ve been online since the early days fondly remember the web of yore — with its flashing banners, wildly distracting backgrounds, and automatic side-scrolling text. But there was a time before the worldwide web and the Internet as we recognize it today, and the way of communicating in this before-time was through Bulletin Board Systems, or BBS. There are still some who can cite this deep magic today, and this page is perhaps the definitive guide to this style of retrocomputing.

This how-to is managed by [Blake.Patterson] who is using a wide variety of antique machines and some modern hardware in order to access the BBSes still in service. He notes in this guide that it’s possible to use telnet and a modern computer to access them, but using something like an Amiga or Atari will give you the full experience. There are some tools that convert the telephone modem signals from that original hardware to something that modern networking equipment can understand, and while the experience might be slightly faster as a result, it does seem to preserve the nostalgia factor quite well.

For those looking for more specific guides, we’ve featured [Blake]’s work a few times in the past, once with an antique Epson PX-8 laptop and again with a modern ESP8266. It doesn’t take much computing power to get connected to these old services, so grab whatever you can and start BBSing!

NABU PC – A 1984 Z-80 Computer You Can Buy Today

November 28, 2022 by Adam Fabio 63 Comments

Want to hack on brand new 8-bit 1980s hardware? Until recently you needed a time machine, or deep pockets to do this. All that has recently changed with the NABU PC. A retro machine that can be bought brand new for $59.99, (plus shipping) no time machine needed.

[Adrian] has one in his Digital Basement, and breaks it all down for us. The NABU PC was a Canadian computer. Designed to connect to the cable TV network, the standard system had no internal secondary storage. You read that right; the NABU used the cable network to download and play games, view documents — just about anything you’d want to do with a computer. Cable modems back in the 80s — maybe someone did have a time machine?

Unfortunately, the NABU network failed. Not due to the PC’s hardware, but because the cable system back then was not designed for bidirectional data. While the NABU PC did see a limited release in Canada, was never widely successful. When production was shut down, the machines couldn’t be liquidated, as they didn’t do anything without the network. So in the warehouse, they sat, until this month, where can find them being sold on eBay.

So what’s inside a NABU? It starts with a Z-80 CPU sporting 64 kB of RAM. A TMS9918 handles video, while a General Instrument AY-3-8910 does the sound. There are also two UARTs. An 8251 for serial io to the keyboard and joysticks, and a high-performance UART chip to handle comms with the network adapter. The keyboard is loaded with good old ALPS switches, and [Adrian] found it rather impressive.

That’s all well and good, but what can you actually do with a NABU PC? Right now, not much. The ROM software comes up and looks for the network adapter, then complains when it doesn’t find it. This means it’s hacking time! An army of retrocomputing enthusiasts are already working on bringing back the NABU computer. Check [Adrian]’s video description for all the documentation links, and check here on Hackaday for the latest updates!

This isn’t our first time watching this sort of liquidation — remember the HP touchpad?

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Silicon Sleuthing: Finding A Ancient Bugfix On The 8086

November 28, 2022 by Al Williams 31 Comments

Few CPUs have had the long-lasting influence that the 8086 did. It is hard to believe that when your modern desktop computer boots, it probably thinks it is an 8086 from 1978 until some software gooses it into a more modern state. When [Ken] was examining an 8086 die, however, he noticed that part of the die didn’t look like the rest. Turns out, Intel had a bug in the original version of the 8086. In those days you couldn’t patch the microcode. It was more like a PC board — you had to change the layout and make a new one to fix it.

The affected area is the Group Decode ROM. The area is responsible for categorizing instructions based on the type of decoding they require. While it is marked as a ROM, it is more of a programmable logic array. The bug was pretty intense. If an interrupt followed either a MOV SS or POP SS instruction, havoc ensues.

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MikroLeo, A 4-Bit Retro Learning Platform

November 27, 2022 by Dave Rowntree 24 Comments

MikroLeo is a discrete TTL logic-based microcomputer intended for educational purposes created by [Edson Junior Acordi], an Electronics Professor at the Brazilian Federal Institute of Paraná, Brazil. The 4-bit CPU has a Harvard RISC architecture built entirely from 74HCT series logic mounted on a two-sided PCB using only through-hole parts. With 2K words of instruction RAM and 2K words of addressable RAM, the CPU has a similar resource level to comparable machines of old, giving students a feel for how to work within tight constraints.

Simulation of the circuit is possible with digital, with the dedicated PCB designed with KiCAD, so there should be enough there to get cracking with it. Four 4-bit IO ports make interfacing easy, with dedicated INput and OUTput instructions for the purpose. An assembler, compiler, and emulator are all being worked on (as far as we can tell) so keep an eye out for that, if this project is of interest to you.

We like computers a bit around these parts, the “hackier” and weirder the better. Even just in the 4-bit retro space, we’ve seen so many, from those built around ancient ALU chips to those built from discrete transistors and diodes, but you don’t need to go down that road, an emulation platform can scratch that retro itch, without the same level of pain.

Portable Commodore 64 Lives!

November 27, 2022 by Al Williams 17 Comments

When you think of a luggable computer, you might think of the old Compaq or — if you are old enough — a Kaypro. But you don’t see as many Commodore SX-64 computers. [The 8-Bit Guy] has wanted one for a while and finally got one, but it wasn’t working. No problem! Just fix it!

The device actually looks sleek compared to some other portables of the era and had a color screen, but — probably due to the price — they didn’t sell very well. The outside of the device looked pretty clean other than some loose screws and clips. The space key was quite yellow but at least there was a keyboard cable which is nearly impossible to find anymore.

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