Simh or the The Computer History Simulator like many other emulators/simulators I use is a multiple system emulator.
Here is a list of some of the various simulators. There will be links as they have a page or pages of their own.
- DEC PDP-1 –The first DEC computer and the progenitor of minicomputers.
- DEC 18-Bit Systems — A series of mostly compatible DEC systems from the mid-60s to early 70s. These include the PDP-4, PDP-7 (This machine was what UNIX was originally written on.), PDP-9, and PDP-15.
- DEC PDP-8 — The computer to called a “Minicomputer” and started a whole new class of computing. Where mainframes and even previous “smaller computers” had costs in the hundreds of thousands or even millions of dollars, the PDP-8 cost less than $20,000. It was a simple but ingeniously built 12-bit machine.
- DEC 36-bit Systems — These include the PDP-6 and PDP-10. These machines are mainframe class and although the PDP-10 was a very widely used mainframe and has quite the legacy, I consider most mainframes to be out of both my wheelhouse and scope of study so I will be touching on these only a little bit.
- DEC PDP-11 — This was the ubiquitous mini-computer from the early 60s up to the mid 70s. It is a 16-bit system and it’s CPU design inspired many future CPU’s including the Motorola M68000 series which was used in early Macintoshes, Amigas, the Atari ST, HP 9000 Series 200 and 300, and many others. I will be spending a lot of time on the PDP-11 especially since there were almost a dozen different OSes for it and it was the first computer that used AT&T Research UNIX and the Berkeley Software Distribution (henceforth, simply called BSD). The legacy of the PDP-11 is ongoing and some Canadian Nuclear Energy Plants still use them for critical legacy applications.
- DEC VAX — This long lived series of computers consisting of both minicomputers and workstation are frankly one one of my favorites. My emulation discussion will begin here. The three main OSes for the VAX are (DEC’s own version of UNIX, BSD, and DEC’s flagship OS, VMS. It is a very unique OS, it is nothing like OSes that came before or after it. Or is it? Cool fact, Dave Cutler, the principal designer of VMS eventually left DEC went to Microsoft and used many of his OS paradigm ideas in Windows NT. So you could say VMS is the great, great granddaddy of Windows 11. We will mostly be working with VMS and ULTRIX, but since there is already a lot of information on emulating BSD on the VAX out there we will will only touch a little on that.
- IBM Mainframes — There are many IBM mainframes that Simh emulates but since most of them are batch systems and I know little about them, I will be spending very little time on them. Systems included are the 1401, the 7000 series, the 360, 370, and a few others.
- IBM 1130 — This smaller IBM computer is kind of unique and had piqued my interest. So, I will be spending some time on these.
- HP Minicomputers — The two that SImh emulates are the 1000 Series and the 3000. I will be spending some time on the 1000 Series using Roberto Sancho Villa’s panelsim. More on this later.
- Altair Z80 and other early microcomputers — There are two simulators for these. I will be eventually expanding this area because there is lot to emulate and they are a lot of fun.
- There are others and if I have time I may cover some of them.