IBM’s Early PC Attracts Time Travelers

August 23, 2022 by Al Williams 51 Comments

It wasn’t long ago I was nostalgic about an old computer I saw back in the 1980s from HP. It was sort of an early attempt at a PC, although price-wise it was only in reach for professionals. HP wasn’t the only one to try such a thing, and one of the more famous attempts was the company that arguably did get the PC world rolling: IBM. Sure, there were other companies that made PCs before the IBM PC, but that was the computer that cemented the idea of a computer on an office desk or at your home more than any computer before it. Even now, our giant supercomputer desktop machines boot as though they were a vintage 1981 PC for a few minutes on each startup. But the PC wasn’t the first personal machine from IBM and, in fact, the IBM 5100 was not only personal, but it was also portable. Well, portable by 1970s standards that also had very heavy video cameras and luggable computers like the Osborne 1.

The IBM 5100 had a brief three-year life from 1975 to 1978. A blistering 1.9 MHz 16-bit CPU drove a 5-inch CRT monitor and you could have between 16K and 64K of RAM along with a fair amount of ROM. In fact, the ROMs were the key feature and a giant switch on the front let you pick between an APL ROM and a BASIC ROM (assuming you had bought both).

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Your Own IBM Mainframe (or Vax, Or Cray…) The Easy Way

June 19, 2022 by Al Williams 34 Comments

If you want the classic experience of working with an IBM mainframe or another classic computer like a DEC VAX, you have a few choices. You could spend a lot of money trying to find one, transport it, and refurbish it. But, of course, most of us will settle for an emulator. While there are great emulators out there, most of the time you aren’t interested in running just the bare machine — you want the operating systems, the compilers, and the other software that made these machines so interesting. Running your three lines of machine code isn’t as much fun as playing hunt the wumpus or compiling some Fortran IV code. Unfortunately, finding copies of all this old software can be daunting. But thanks to the efforts of [Rattydave], you can do it with no problems at all. The secret? Pre-built docker images that have everything you need in one place.

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Custom 40% Model F Keyboard Is 100% Awesome

June 16, 2022 by Kristina Panos 41 Comments

Look closely at this beauty. No, that’s not a chopped IBM Model M or anything — it’s a custom 40% capacitive buckling spring keyboard with an ortholinear layout made by [durken]. Makes it easy to imagine an alternate reality where IBM still exists as IBM and has strong keyboard game, or one where Unicomp are making dreams come true for those who don’t need anywhere near 101 or 104 keys.

Buckling what now? This lovely board uses capacitive buckling spring switches from an old IBM Model F. Basically, every time you press a key, a little spring is bent over (or buckled) in the name of connectivity. In the capacitive version, the spring pushes a hammer onto a pair of plates, causing a change in capacitance that gets recognized as a key press. In this case, those key presses are read by a TH-XWhatsit controller.

Using a Model F XT’s PCB as a guide, [durken] made a field of capacitive pads on one PCB, and made a second, ground plane PCB to avoid interference. In a true homage to these keyboards, [durken] decided to curve the PCB slightly, which naturally complicated almost everything, especially the barrel plate.

The solution was to make a separate barrel plate that slides into the case and gets screwed to the top via mounting bracket. For an extra bit of fun, [durken] mounted an SKCL lock switch under the IBM logo which enables solenoid mode. Be sure to check that out in the (updated!) video after the break.

One of the best things about a buckling spring keyboard is that each key sounds slightly different. Not so in solenoid mode, unless you were to use multiple solenoids.

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Have You Heard Of MCGA?

June 2, 2022 by Jenny List 21 Comments

In the world of PC graphics, the early standards followed the various video cards of the day. There was MDA, familiar through the original text-based DOS prompt, CGA, then EGA, and the non-IBM Hercules along the way. Finally in 1987 IBM produced the VGA, or Video Graphics Array standard for their PS/2 line of computers, which became the bedrock on which all subsequent PC graphics cards, even those with digital outputs, have been built. It’s interesting then to read an account from [Dave Farquhar] of the other now-forgotten video standard that made its debut with the PS/2, MCGA, or Multicolor Graphics Array. This was intended as an entry-level graphics system to compete with the more multimedia-oriented home computers of the day such as the Commodore Amiga and Atari ST.

Offering 320×200 graphics at 256 colors but only two colors at 640×480 it’s difficult to see how it could have been a viable competitor to the Amiga’s 4096-color HAM mode, but it did offer the ability to drive an RGB monitor through its VGA-like socket. The story goes that IBM intended it to provide an upgrade incentive for PS/2 customers to buy a more powerful model with VGA, but in the event a host of third-party VGA-compatible cards emerged and allowed more traditional ISA computers from third parties to retain a competitive edge and eventually sideline the PS/2 line entirely.

We called time on VGA back in 2016, and it’s fair to say that it’s disappeared from PC hardware since then even if much of its technologies still lurk within. It’s pleasing to see though that it remains a stalwart of hacked-together display interfaces, with efforts such as this 7400-based VGA card continuing to impress us.

Striping A Disk Drive The 1970 Way

May 16, 2022 by Al Williams 37 Comments

These days, mass storage for computers is pretty simple. It either uses a rotating disk or else it is solid state. There are a few holdouts using tape, too, but compared to how much there used to be, tape is all but dead. But it wasn’t that long ago that there were many kinds of mass storage. Tapes, disks, drums, punched cards, paper tape, and even stranger things. Perhaps none were quite so strange though as the IBM 2321 Data Cell drive — something IBM internally called MARS.

What is a data cell you might ask? A data cell was a mass storage device from IBM in 1964 that could store about 400 megabytes using magnetic strips that looked something like about a foot of photographic film. The strips resided inside a drum that could rotate. When you needed a record, the drum would rotate the strip you needed to the working part and an automated process would remove the strip in question, wrap it around a read/write head and then put it back when it was done.

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Retrotechtacular: The IBM System/360 Remembered

May 13, 2022 by Al Williams 50 Comments

Before IBM was synonymous with personal computers, they were synonymous with large computers. If you didn’t live it, it was hard to realize just how ubiquitous IBM computers were in most industries. And the flagship of the mainframe world was the IBM System/360. For a whole generation that grew up in the late 1960s and early 1970s, a 360 was probably what you thought of when someone said computer. [Computer History Archive Project] has a loving recollection of the machine with a lot of beautiful footage from places like NASA and IBM itself. You can see the video below.

Not only was the 360 physically imposing, but it had lots of lights, switches, and dials that appealed to the nerdiest of us. The machines were usually loud, too, with a Selectric terminal, card punches and readers, noisy 9-track tape drives, and a line printer or two.

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IBM PCjr Types Again, Thanks To KeybJr

April 24, 2022 by Donald Papp 6 Comments

Most of us think of keyboards — even vintage ones — as being fairly standardized and interchangeable, but that isn’t the case for the IBM PCjr. Its keyboard was quite unlike most others of its time, which means that a PCjr without an original keyboard is pretty much a dust collector. That’s what led [Jozef Bogin] to create the KeybJr, a piece of hardware that allows one to use any AT, XT, or PS/2 keyboard with the IBM PCjr.

The PCjr’s oddball keyboard can be a bit of a hassle for vintage computing enthusiasts.

What was strange about the PCjr’s keyboard? From the outside it looked pretty normal, but it definitely had its own thing going on. For one, the PCjr keyboard operated over a completely different protocol than the other keyboards of the time. In addition, its connection to the host was either by IR, or via its own wired cable adapter.

The KeybJr solves this by using an Arduino-based board to turn inputs from other keyboards of the time into something the PCjr expects. These signals are sent out and received either over infrared, or by the PCjr’s “K” port for a wired keyboard link.

Why bother with the IR functionality? Well, the connector and pins on the PCjr are not very rugged, and sometimes they are damaged. In those cases, it is nice to have the option of using a normal (for the time) keyboard over the IR link. Vintage hardware is not always in perfect shape, after all. That’s why things like ATX power supply adapters for the PCjr exist.

Want to give it a shot? There is a GitHub repository for the KeybJr, and you can see it in action in a brief video, embedded below.

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