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ALTAIR: Reads of uninstalled memory are supposed to return 0377 (0xff). However,

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memory bytes beyond the installed limit were being initialized with 0
instead of 0377. Fix comment and the actual initialization loop.
This commit is contained in:
Scott Bailey 2015-02-02 16:27:39 -05:00 • committed by Mark Pizzolato
parent 94b1da0a53
commit d8b55677c1
1 changed files with 3 additions and 2 deletions
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5
ALTAIR/altair_cpu.c
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@ -25,6 +25,7 @@
cpu 8080 CPU cpu 8080 CPU
02-Feb-15 RSB Fixed initialization of "uninstalled" memory
19-Mar-12 RMS Fixed data type for breakpoint variables 19-Mar-12 RMS Fixed data type for breakpoint variables
08-Oct-02 RMS Tied off spurious compiler warnings 08-Oct-02 RMS Tied off spurious compiler warnings
@ -67,7 +68,7 @@
3. Non-existent memory. On the 8080, reads to non-existent memory 3. Non-existent memory. On the 8080, reads to non-existent memory
return 0377, and writes are ignored. In the simulator, the return 0377, and writes are ignored. In the simulator, the
largest possible memory is instantiated and initialized to zero. largest possible memory is instantiated and initialized to 0377.
Thus, only writes need be checked against actual memory size. Thus, only writes need be checked against actual memory size.
4. Adding I/O devices. These modules must be modified: 4. Adding I/O devices. These modules must be modified:
@ -1175,7 +1176,7 @@ for (i = val; i < MEMSIZE; i++) mc = mc | M[i];
if ((mc != 0) && (!get_yn ("Really truncate memory [N]?", FALSE))) if ((mc != 0) && (!get_yn ("Really truncate memory [N]?", FALSE)))
return SCPE_OK; return SCPE_OK;
MEMSIZE = val; MEMSIZE = val;
for (i = MEMSIZE; i < MAXMEMSIZE; i++) M[i] = 0; for (i = MEMSIZE; i < MAXMEMSIZE; i++) M[i] = 0377;
return SCPE_OK; return SCPE_OK;
} }