Double Buffer RK11-C

Noel Chiappa jnc at
Tue Dec 6 09:51:56 CST 2016

    > From: Glen Slick

    > You should also hang out at vcfed forum in addition to hanging out here.

I barely have time to keep up with the things I'm already into (actually,
strike that - I _don't_ have time to keep up already :-)! So I'm going to
have to pass.

Interesting about the FP11 stuff, though. I wonder, however, if those 11/20
mentions are more aspirational, rather than something that was actually done,
and later dropped? I say this knowing a modest amount about how the KA11 CPU
in the 11/20 works, and a bit about how the FP11-B interfaces to the host CPU.

For one thing, it would take some modifications to the KA11 to recognize
floating point instructions, so that it can wake up the FP11-B to handle
them. But that turns out to be the easy part; it would take further mods to
the KA11 because the FP11-B expects the host CPU to do data fetches, etc on
its behalf. (See Figure 2-3 in the FP11-B MainManual.) This latter function
can't be off-loaded onto a separate interface unit, as it needs access to
register contents held in the CPU.

I don't have the time to look into this further, but if someone is interested
they'd need to study the FP11<->CPU interface, and in particular look at how
the KB11 supports memory operations requested by the FP11-B - I wouldn't be
suprised if there's some microcode in the KB11 to support those memory


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