[quietbritishjim]

> instruction set consisting of Ada Primitives like "Define a type for a variant structure with 3 variants, you'll get the details later".

Wow, it's hard for me to imagine a CPU with such high level instructions. Were these per-process, like virtual memory on a modern processor? Or was there only expected to be one executable running on the machine at a time?

> My Covid19 project was writing a software emulation of it,

Where did you get to? Do you have a link?

[TheOtherHobbes]

The microcoding means you have fairly standard CPU hardware - an ALU, some registers, memory ports, and so on - and the microcode sequences it to emulate the ISA.

So it's not that the ADA primitives were baked directly into TTL.

It's somewhat related to the Itanium model where the compiler generates a Very Long Instruction Word.

Microcode is a standard way of implementing CISC, but this machine took it further than usual.

[phkamp]

"fairly standard" is a bit of an understatement in this particular case.

The machine actually has both an ALU as we know it, called the "VAL" board, but it also has a second unit, which runs in parallel on the "TYP" board, which does checks and operations on the data types of the data on the VAL board.

That means that the compiler can just emit a "ADD" instruction, and leave it to the microcode to figure out if it is adding two floating point numbers, two integers or a floating-point plus an integer and if the numeric type has a range, the result will be checked to fit inside that range.

So the comparison to the Itanic is not helpful. Itanic was a pretty standard CPU which forced a lot of constraints and complexity into the compiler.

The R1000 does the opposite: The compiler gets to emit code which operates on the types as the Ada language defines and knows them, and the hardware+microcode translates that into action.

Grady Booch donated some internal documents to us, and they contain a couple of references to "Incredibly Complex Instruction Set Computer" and they're not half wrong about that.