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Having run the device code thru XXDP and some other OS's and scenarios
rigorously, a bunch of discrepancies were found, which need to be addressed
by this rather extensive patch.
1. Each unit must implement its own "drive status" register, to be able to
track per-drive errors / conditions correctly;
2. Fixed INT_SET() / INT_CLR() in RPCS write function (wrong order of the "if"
conditions);
3. Some behavior was implemented not exactly how it was expected from the real
hardware, such as:
a. Post-I/O register values in RPDA and RPCA (including the corner case of
pack overflow);
b. I/O stacking, which wasn't mentioned in any available documentation, but
only XXDP listings;
c. RESET/IDLE function must be accepted for a "busy" controller;
d. HOME function must always execute, even when "device ready" is not set
(e.g. when SEEK error detected);
e. SEEK incomplete should not respond with "device ready" (however, the
condition can be cleared by HOME, d.);
f. WLOA-induced write-lock violation wasn't reflected in "device status".
4. Some timing was off so that the device worked "too fast" -- this was fixed
(except for the pathological cases when the races are in the actual test
code, and cannot be logically fixed);
5. WLOA setup command bug was fixed;
6. Added more code comments found per the above peculiarities.
Open SIMH machine simulator
This is the codebase of SIMH, a framework and collection of computer system simulators.
SIMH was created by Bob Supnik, originally at Digital Equipment Corporation, and extended by contributions of many other people. It is now an open source project, licensed under an MIT open source license (see LICENSE.txt for the specific wording). The project gatekeepers are the members of the SIMH Steering Group. We welcome and encourage contributions from all. Contributions will be covered by the project license.
The Open SIMH code base was taken from a code base maintained by Mark Pizzolato as of 12 May 2022. From that point onward there is no connection between that source and the Open SIMH code base. A detailed listing of features as of that point may be found in SIMH-V4-status.
PLEASE NOTE
Do not contribute material taken from github.com/simh/simh unless you are the author of the material in question.