Anton Aylward wrote:
James Knott said the following on 01/15/2012 09:37 AM:
I have worked at the machine level on several types of CPU and never seen such a "loop counter". On the other hand, a general purpose register that could handle that function, among many others has been part of every one and would be essential in any useful computer, unless all operations were performed in memory.
"Part" being the operative word. Not all machines had all registers as 'general purpose' as the old 404, 8080 and z-80 demonstrated.
Yes, the series/360 and the PDP-11 and their look-alikes the Z-8000 and z-80000 had all programmer accessible registers "general purpose (except when they were 'stacked' or aliased to floating point), but there were many exceptions.
There are plenty of CPUs with registers dedicated for special purposes. -- Per Jessen, Zürich (-2.1°C) -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org