Which Dec Emulation is the MOST useful and Versatile?
paulkoning at comcast.net
Mon Oct 30 11:43:51 CDT 2017
> On Oct 27, 2017, at 5:00 PM, Phil Blundell via cctalk <cctalk at classiccmp.org> wrote:
> On Fri, 2017-10-27 at 13:38 -0700, Brent Hilpert via cctalk wrote:
>> I wonder if they were just trying to draw an analogy between the
>> inherent dynamic operation requirements of magnetic logic and the
>> dynamic operation requirements of some (many?) NMOS designs (not
>> really inherent to NMOS).
> On the subject of NMOS dynamic logic, someone recently pointed out a
> paragraph in the technical manual for a 1990s ARM2-based computer which
> warned of dire consequences, including possibly destruction of the
> chipset, if the circuitry was left powered with the clock stopped for
> more than a second or two.
> Obviously if the clock is stopped for more than a few hundred
> microseconds then the logic will start to lose its marbles and the
> system will need a reset to recover. But I don't think I've previously
> heard any suggestion that dynamic logic ICs would actually be damaged
> or destroyed under these circumstances. I can just about imagine that
> there might be some situation where an invalid internal state would
> result in a short circuit between power and ground, but that's just
> supposition really. Anybody know of a case where something bad has
> actually happened?
I don't understand this at all. "Dynamic logic" is not a familiar concept, and certainly the NMOS logic I know isn't dynamic. Memory (DRAM) is dynamic, and will forget if you don't refresh it. But DRAM doesn't mind if you stop the clock, it just won't remember its data.
So I don't know how you might have a logic design that "loses its marbles" if you stop the clock. And anything that is fried by clock loss is, in my view, the work of someone who should not be allowed anywhere near a EE shop.
Incidentally, while "soft core" magnetic logic is dynamic, memory core logic is not. You could slow that down and it would still work. The signals are pulses, not levels, but the pulses will still happen with a 1 Hz clock.
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