OT(?): Emulation XKCD

[Zane Healy]

> On Oct 30, 2019, at 2:35 PM, Charles Anthony via cctalk <cctalk at classiccmp.org> wrote:
> 
> For the dps8 emulator, I wrote (for expediency) the I/O code to complete
> immediately. When the CPU executes an I/O instruction, the I/O is completed
> and the interrupt posted before the next instruction is executed. As the
> emulator was (at that point) single threaded, there was no performance
> reason to do otherwise, and delaying interrupt delivery was additional code
> that I didn't want to write and debug. The consensus in the Multics
> community was that this was *probably* OK; the interrupt structure was
> robust and the interrupt handling code well written, and should be able to
> cope. But everytime a runtime failure occured, the question popped up: is
> zero-latency I/O the issue?  I ended up adding code to delay interrupt
> delivery as a run-time configuration option so that that possibility could
> be checked.
> 
> The XKCD is dead on for me. I have had that conversation.
> 
> -- Charles

If you’re on this list, does this mean this is a good place to ask Multics questions? :-)  Yes, I have a couple.

Zane