PERQ Emulator Progress (of sorts)!
ard at p850ug1.demon.co.uk
Wed Nov 7 17:58:14 CST 2007
> 951). Of course, I obviously still have a ways to go. As evidenced by
> the completely garbled text, I have yet to get the PERQ's unique (and
> extremely complicated) RasterOp hardware emulated to any significant
Good luck, you'll need it :-). The rasterop hardware is conceptually very
simple, and practically very complicated. The timing of just about
everything is critical, as you must know by now, the machine has a
4-state counter (basically counting through the 4 16-bit words that make
up a 'quadword', the memory hardware and video shift registers being 64
bits wide, whereas the path to the CPU is 16 bits wide). It's possible,
although not really documented, to do a read-modify-write cycle on a
quadword _and the data transfers overlap_ -- IIRC there's a 2 clock delay
between them. And that's exactly what the rasterop hardware does.
The Rasterop microcode is intrictate to say the least....
I asusme you've read the schematics and the techref. Have you seen the
Rasterop microcode? And the filksong?
> degree. And after that I have a ton of hardware details to work out.
> But this is a major milestone, and I'm so excited that I just had to
> share my excitement with someone... I never thought I'd get anywhere
> near this far with the emulation, given how complicated the PERQ is.
> And if I've seen so far, it's because I've been standing on the
> shoulders of giants. Or one giant, at least -- our own Tony Duell who's
> been ever-so-patient with my questioning and who probably knows more
> about the PERQ hardware than the original designers did...
That much I really doubt... Mind you, even if I say so myself, I think I
understnad the hardware fairly well. And I have written microcode...
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