[bitwize]

The Tandy 2000 was one. It was a PC-ish, DOS-running machine that was more powerful than anything put out by IBM at the time, but not PC compatible. The 186 had additional on-chip hardware like timers, etc. that the 8086 (and 286 and subsequent chips) did not, and some of these were mapped to I/O address space that corresponded to different PC hardware, so building a fully PC compatible machine with a 186 was near impossible.

Forgoing PC compatibility was not without its advantages. The Tandy 2000 could have up to 768k of RAM -- and used all of it, the 640k limit being nonexistent. This made a huge difference in applications such as Lotus 1-2-3. The Tandy 2000 also featured a 640x400 color display option -- extremely high resolution for the time -- at an affordable price, making it attractive as a graphical workstation. Tandy 2000s were used in the design of Stars and Stripes 87, an America's Cup winning yacht, and were also used to prototype color display in Windows 1.0. So it was an important machine, despite fading into obscurity due to its lack of PC compatibility.

Sorry, I just frickin' love this machine and wish it were more remembered.

[bikenaga]

Actually, you could go up to 896KB - it was not officially supported by Tandy, but there was a guy in Washington who had a company called Envision Designs that did this.

https://archive.org/stream/PortableComputingMagazineAug1985/...

I think I read about him first in Jerry Pournelle's coolumn in BYTE. So he modded my 2000 up to 896KB, and also added a disk controller and hard drive. Tandy eventually started selling cards with an 8087, which definitely helped with floating point stuff.

It was a wonderful machine. I first ran Turbo Pascal on it, did my first color Mandelbrot set. I had the color monitor and the inkjet printer. What is incredible is that for what I spent in 1984 dollars on all that stuff, adjusted for inflation, I could probably now get dual Xeons with 20 cores!

It was a very sad day when I realized that it was getting too hard to deal with the incompatibility with the IBM-PC standard. The video RAM (and 640 x 400 8-color graphics), the nonstandard floppy disks, the add-on cards (which could be installed without opening the case), ... Technical superiority isn't always conclusive.

The original BYTE review, for anyone who's interested:

http://tech-insider.org/personal-computers/research/acrobat/...

[bitwize]

Yeah, those tray-like expansion cards were neat. Too bad that idea never caught on, and there were only a few expansion cards (all by Tandy) available for the machine.

PC compatibility basically steamrolled over all that. Maybe it was seeing what happened with the 2000 that convinced me from an early age that PCs were going to conquer the world, and Macintosh and Amiga fanboys were next on the chopping block. I couldn't even guess then how right I'd be; not even game consoles avoided turning into cut-down, purpose-built PCs.

At the time, I was just disappointed that the only graphical game that actually worked with the 2000 was a specially ported Flight Simulator 1.0.

[bikenaga]

The latch-things that were supposed to secure the cards in the slots apparently didn't seat the cards tightly enough. My dealer finally just replaced them with screws after I complained a few times about the graphics card coming loose, resulting in a poor signal.

Compatibility has been great in some ways. But with standards in flux back then, there was more variety (and maybe fun) than there is now. Besides experiments like the 2000, there were things like machines with 2 different CPUs (the Commodore SuperPet had a 6502 and a 6809, and I think the DEC Rainbow had a Z80 and and 8088). There were so many 5.25" floppy formats you needed utilities like Xenocopy to convert among them (I think it fiddled with the drive controller to manipulate the drive heads).

With machines being simpler, you could fiddle a lot more. Many magazines published assembly language code for little games and utilities; for that matter, the computer section of a typical bookstore carried lots of books on assembly language. There were books on microcomputer system design, stuff about how things worked at the chip level. All gone.

I remember Flight Simulator. I couldn't believe it the first time I played it. Crashed the plane over and over ... There was a graphical paint program, and other graphical stuff which worked with the very slow mouse - in fact, I have a copy of an ad featuring Bill Gates in which he describes using the 2000 in designing the early versions of Windows.

[bitwize]

I'm a bit surprised that in your list of dual-CPU systems you didn't mention Tandy's own Model 16 -- which was a TRS-80 Model II fitted with a 68000 daughtercard and up to 768KiB RAM for the secondary processor. It was the first Unix-capable desktop not to come out of Sun.