retrocomputing

384 Articles

The 4004 Upgrade You’ve Been Waiting For

March 26, 2023 by 5 Comments

You know how it is. You have an older computer, and you can’t run the latest software on it. Time to upgrade, right? Well, if you have been in this situation a very long time, [ryomuk] may have an answer for you. The emu8080on4004 project (Google Translate) offers a way to run 8080 code on a 4004 CPU. Finally!

The 4004 development board is a homebrew affair, and the emulator works well enough that an 8080 Tiny BASIC interpreter ran with very few changes to the source code. You can see it working in the video below. It would be cool to run CP/M, but we imagine that would be a little harder, especially resource-wise.

A few things are missing. For example, the DAA instruction doesn’t exist, and there are no provisions for interrupts. There’s only one I/O port, and using the IN instruction will block until you receive a serial port character. There is an option to implement the parity flag in the 8080 flags register, but its operation is untested.

Still, pretty impressive for a 4-bit CPU running at 740 kHz with very little memory. If you want to see more about the development board itself, check out the second video below. Want to know more about the chip that launched a family of processors that is still around? Read its biography. You can also read about the designer who put his signature on the die.

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A Love Letter To The Sphere Computer

March 11, 2023 by 21 Comments

[Ben Z] loves the Sphere computer, a very early entry in the personal computer boom of the mid 1970s. The 6800 CPU was unique in its day that it was a full system — at least in theory. If you could afford the whole system, you got a nice case with a keyboard and a memory-mapped display board. You can see a great video tour of the system below the break.

The Sphere suffered from a few problems, none of which were easily foreseeable by its designer. First, the 6800 didn’t get the traction that the 8080-derived CPUs did. Second, the S-100 bus would prove to be popular but that nearly always meant an 8080-type processor in practice. Third, while an all-in-one system was the right idea, it was pricey at the time, and many people would opt for something less expensive even if it had less capability. People also wanted to leverage hardware they may have already had. It was easier to imagine hooking up a surplus TeleType, for example, to a more conventional computer than to a Sphere that expected its own display hardware and keyboard.

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The First Gui? Volscan Controls The Air

March 9, 2023 by 10 Comments

In the 1950s,  computers were, for the most part, ponderous machines. But one machine offered a glimpse of the future. The Volscan was probably the first real air traffic computer designed to handle high volumes of military aircraft operations. It used a light gun that looked more like a soldering gun than a computer input device. There isn’t much data about Volscan, but it appears to have been before its time, and had arguably the first GUI on a computer system ever.

The Air Force had a problem. The new — in the 1950s — jets needed long landing approaches and timely landings since they burned more fuel at lower altitudes. According to the Air Force, they could land 40 planes in an hour, but they needed to be able to do 120 planes an hour. The Whirlwind computer had proven that computers could process radar data — although Whirlwind was getting the data over phone lines from a distance. So the Air Force’s Cambridge Research Center started working on a computerized system to land planes called Volscan, later known as AN/GSN-3.

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Pi Picos Give Casio FX9000P Its Memory Back

March 8, 2023 by 12 Comments

Is the Casio FX9000P a calculator or a computer? It’s hard to tell since Casio did make calculators that would run BASIC. [Menadue] didn’t know either, but since it had a CRT, a Z80, and memory modules, we think computer is a better moniker.

He found one of these, but as you might expect, it needed a bit of work. There were two bad video RAM chips on the device, and [Menadue] used two Raspberry Pi Picos running a program to make them think they are RAM chips. The number of wires connecting the microcontollers might raise some eyebrows, but it does appear to get the job done.

He also used more Picos to emulate memory on cartridges. Then he used a test clip and a — you guessed it — another Pico to monitor the Z80 bus signals. It is amazing that the Pico can replace what would have been state-of-the-art memory chips and a very expensive logic analyzer.

The second video mostly shows the computer in operation. The use of Picos to stand in for so much is clever. It reminded us of the minimal Z80 computer that used an Arduino for support chips. The computer itself, though, reminded us more of a cheap version of the HP9845.

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Assembly Language 80’s Minicomputer Style

March 6, 2023 by 19 Comments

In the days before computers usually used off-the-shelf CPU chips, people who needed a CPU often used something called “bitslice.” The idea was to have a building block chip that needed some surrounding logic and could cascade with other identical building block chips to form a CPU of any bit width that could do whatever you wanted to do. It was still harder than using a CPU chip, but not as hard as rolling your own CPU from scratch. [Usagi Electric] has a Centurion, which is a 1980s-vintage minicomputer based on a bitslice processor. He wanted to use it to write assembly language programs targeting the same system (or an identical one). You can see the video below.

Truthfully, unless you have a Centurion yourself, the details of this are probably not interesting. But if you have wondered what it was like to code on an old machine like this, you’ll enjoy the video. Even so, the process isn’t quite authentic since he uses a more modern editor written for the Centurion. Most editors from those days were more like CP/M ed or DOS edlin, which were painful, indeed.

The target program is a hard drive test, so part of it isn’t just knowing assembly but understanding how to interface with the machine. That was pretty common, too. You didn’t have a lot of help from canned routines in those days. For example, it was common to read an entire block from a hard drive, tape, or drum and have to figure out what part of it you were actually interested in instead of, say, opening a file and reading a stream of characters.

If nothing else, fast forward over to the 25-minute mark and see what a hard drive from that era looked like. Guess how much storage was on that monster? If you guessed more than 10 MB, you probably didn’t live through the 1980s. We won’t even guess what the price tag was, but you can bet it was spendy.

If you think entering programs like this is painful, try a front panel. That made paper tape seem like a great thing.

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SCSI: The Disk Bus For Everything

March 2, 2023 by 72 Comments

Early home PCs usually had a floppy disk and a simple hard drive controller. Later, IDE hard drives became the defacto standard. Of course, these days, you are more likely to find some version of SATA and — lately — NVME connectors. But a standard predating all of this was very common in high-end systems: SCSI. [RetroBytes] recently did a video on the bus which he calls the “USB of the 80s.”

Historically, Shugart — a maker of disks — was tired of producing custom drive electronics for each device they made. Instead, they made disks with a standard interface and then produced a single interface board for each computer they wanted to support. The interface was very generic, and they were able to get it standardized with ANSI — an early example of the benefit of opening up a standard.

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Emulating All The TRS-80 Software

February 27, 2023 by 37 Comments

Even if you didn’t own a TRS-80, the widespread footprint of Radio Shack in malls meant that if you are old enough, it is a good bet you have seen one and maybe even played with one. The games were crude, but state-of-the-art for 1982. If you wanted business software, that was there too, just don’t expect much on any of the personal computers of the day. My old TRS-80 Model III doesn’t boot anymore and is waiting for me to find time to pull it apart. But it turns out you can run all those old programs with almost no effort. If you’ve experimented with emulators before, you know there are two major problems. First, you need to install the sometimes-fidgety emulator. Second, you need to find the software you want to run and probably convert it into some format the emulator will read. The website named The Big List of TRS-80 Software solves both problems.

You are probably thinking this doesn’t solve any problem because it is just a list of links to software. That’s a reasonable thing to think, but we think the website really needs a new name. There are 15,873 pieces of software on the site, although some of them are duplicates or multiple versions of a single program. You can download them in a format that is useful for some emulators or, in some cases, the original files. But here’s the kicker. You can also click to launch a virtual TRS-80 in your browser and start the program.

Sounds great, right? Well, for the most part, it is. However, some of the programs are finicky and don’t run well in the browser. There’s also the problem of finding the documentation, but you can’t have everything. If you want a quick run of a very common game from back in the day, try Flying Saucers. Continue reading “Emulating All The TRS-80 Software” →