21 Feb
2018
21 Feb
'18
11:37 a.m.
On Feb 21, 2018, at 2:24 PM, Guy Sotomayor Jr <ggs
at shiresoft.com> wrote:
Yes, there may be cases where errors are expected. For example, out of range address
errors, which are used by memory size probing. But wrong-parity errors are far less
likely.
I saw it emulated on Dick Gruene's EL-X8 emulator, and tested by the associated test
program he wrote (which compared bare-metal execution of the test program with execution
of that same program on the emulator, just like what Ray suggested). There is a CWI
report that describes this, its pretty neat. But apart from testing the compleness of his
understanding and the emulation of the "write wrong parity" instruction, it
didn't really add anything useful to any other software. No OS or application I have
found depends on that capability, so our SIMH based emulator omits this and no harm is
done by that omission.
On Feb 21, 2018, at 10:59 AM, Paul Koning via
cctalk <cctalk at classiccmp.org> wrote:
Caching doesn't change user-visible functionality, so I can't imagine wanting to
emulate that. The same goes for certain error handling. I've seen an emulator that
included support for bad parity and the instructions that control wrong-parity writing.
So you could run the diagnostic that handles memory parity errors. But that's a
pretty uncommon thing to do and I wouldn't bother.
I disagree, especially if you?re using an emulator for development. Caching is one of
those things that can go
horribly wrong and not having them emulated properly (or at all) can lead to
bugs/behaviors that are significantly
different from real HW. The same goes for error reporting/handling. There are cases
where errors may be expected
and not having them can cause the SW to behave differently. > ...
However, it is my belief (and I think others have also stated) that assuming infinitely
fast I/O (e.g. no delays what so ever) can cause issues because in many cases the SW
expects to be able to do some work between the time that the I/O is started and when it
completes.