🚀 go-pugleaf

On Friday, August 10, 2018 at 7:10:03 PM UTC-4, Alfred Falk wrote:
> The Data General Nova instruction set was (sort of) admirable for its cut-
> down simplicity.  The DG Eclipse had to be admired for the way they added a 
> lot of useful instructions, while still being 100% compatible with the Nova, 
> but pretty it was not.  Even more so with the 32-bit MV series.

The Nova was an interesting beast and elegant in its own way - quite a step up from the sparseness of the PDP-8, but not all of the bells and whistles (and "special" memory locations) of the PDP-11.

I was a developer on one non-DG operating system for the Nova, and a maintainer for another. Some time later, Data General sent me a stack of my STRs (bug reports) for RDOS and Extended BASIC back, along with a large pile of other people's STRs and source tapes for both, with a note that essentially said "Congratulations! You're now the maintainer." To be fair, I did give them an XBASIC STR that was fundamentally unsolveable (ask if you want the details).

The Eclipse ("Real" Eclipse, not "Big Bird") was pretty clean, too. The Nova 3 and Eclipse S/200 were essentially the same product ('181 ALUs) but the Eclipse had more microcode. Likewise for the Nova 4 and Eclipse S/140 (29K-series ALUs). This all pre-dated studies on instruction set complexity vs. speed (like when DEC found out that a good percentage of the VAX instruction set could be replaced by emulator traps and emulated by the remaining instructions without penalty). As part of maintaining RDOS, I built all of the zillion xRDOS flavors and they all ran about the same speed on my test S/230. So, whenever I was working in a piece of code that had conditionals for different processors, I would optimize out a lot of those special cases.

Don't get me started on Big Bird. It kept the DG from hitting the skids earlier than it did, but it was too little, too late, too expensive (as in "not enough cheaper than a VAX-11/780 to justify going with those oddballs from DG").

Very little is made of the M/600 which was its own kettle of fish, a mini trying to steal market share from the lower end of the IBM 370 product line (mostly Models 115 and 125).

And then there was the mN601. I'd call that an interesting first effort, but the low price of the chip was offset by the rather complicated support circuitry, and if you actually wanted to run regular DG peripherals and software, the price savings over a discrete CPU were small and the performance loss was big.