There are two things that keep me from expanding my collecting old computers: the cost and the space required to house them. I do have my old original TRS-80, and an old serial terminal (see the video below). However, I got rid of my Data General hardware and I lost my old 1802 COSMAC Elf in some flooding. There have been a few replica retro computers of various degrees of fidelity and they are usually cheaper and smaller than the originals. I have a replica Altair, a replica Elf, and a replica KIM-1.

However, it is hard to justify the expense and the cost of either the real things or the replicas. It is even worse with the really large machines, some of which require special power or cooling and are hard to keep running. Another option, of course, is software simulation. Options like SIMH and Hercules work well, but they aren’t always graphical and it is a lot of work to set up a machine just to play with for a few hours or to show a student how it was done in the good old days.

On the other hand, there are quite a few old computer emulators that run right in your browser. No software to install, no hardware to set up, and many of them are graphical. I know a lot of people don’t want to post their work into a “cloud service” but I’m willing to risk my 30 line BASIC program that guesses your number.

PC/OSI – This is actually two different emulators: one for the IBM PC (which is hardly an old computer, by my estimation) and another for the Ohio Scientific Challenger 1P. The site has some preconfigured demonstrations (including Windows 1.0) and you can configure your own, too. Or maybe you’d rather play Wolfenstein and a few other games.

Mac – If Windows isn’t your thing, you might enjoy trying Mac OS 7.

Amiga – The Amiga had a lot of features that were ahead of their time and you can try an Amiga 500 here.

TRS-80 – I still have a model III, but you can run a virtual one in your browser.

COSMAC Elf – The COSMAC Elf was the first computer I personally owned and this site has a very faithful graphical reproduction of the system, along with a few extras.

KIM-1 – The KIM was a very usable single board computer that popularized the 6502. This in-browser version gives you the feel of an early hobby computer.

Altair – You need Java, but this emulator will let you experiment with the computer that arguably started the home and hobby computer market.

PDP/11 – Before Linux there was Unix. This page lets you run the sixth edition of Unix on a virtual PDP/11. The sixth edition is so old, you may need to know that the cd command didn’t exist yet (try chdir). Use the # key to backspace and the @ key to delete a line (pretend you are using a TeleType). If you get tired of the uppercase, read the FAQ linked on the site.

EDSAC – Dr. Wilkes’ EDSAC was one of the first modern computers that was actually operational. His team at Cambridge developed a lot of techniques that we take for granted today. This is a strange machine to program, and you might want to browse the manual for the PC-based emulator to learn more about how to program for it.

ENIAC – If you think the EDSAC is hard to program, try this one (but you’ll need a Java-enabled browser).

I’m sure there are others out there, but that’s enough to get you started and I’m sure the comments will pick up a few more. If you want to appreciate the difference between loading a web page and getting some real hardware working, you can compare the PDP/11 entry to bringing up the real thing. There are also sites where you can hook up to some real old hardware which could be the best of both worlds. For another cross (a modern simulator and a vintage serial terminal), you can see my video below where I try to save the galaxy from Klingons.