#2220 Checkpoints for non-default devices are unreliable

[rice123]

Activate the monitor and execute:

watch 0800 9fff
dev 8:
watch 0600 0700
a 0300 sei
.0301  sta $0600
.0304  jmp $0300
r pc = 0300
x

A watchpoint is triggered as expected:

#2 (Stop on store 0600) 
.8:0301  8D 00 06    STA $0600      - A:FF X:06 Y:FF SP:45 ..-..I.C    2629402

Note the clock number, this code should trigger a watchpoint every 9 cycles. Now keep doing the same thing:

dev C:
x

Result:

(8:$0304) dev C:
Setting default device to `Computer'
(C:$e5cf) x
#2 (Stop on store 0600) 
.8:0301  8D 00 06    STA $0600      - A:FF X:06 Y:FF SP:45 ..-..I.C    2637457
(8:$0304) dev C:
Setting default device to `Computer'
(C:$e5cd) x
#2 (Stop on store 0600) 
.8:0301  8D 00 06    STA $0600      - A:FF X:06 Y:FF SP:45 ..-..I.C    2677363
(8:$0304) dev C:
Setting default device to `Computer'
(C:$e5d1) x
#2 (Stop on store 0600) 
.8:0301  8D 00 06    STA $0600      - A:FF X:06 Y:FF SP:45 ..-..I.C    2717260
(8:$0304) dev C:
Setting default device to `Computer'
(C:$e5cd) x
#2 (Stop on store 0600) 
.8:e5cd  45 06       EOR $06        - A:FF X:06 Y:FF SP:45 ..-..I.C    2757157
(8:$0304) dev C:
Setting default device to `Computer'
(C:$e5cf) x
#2 (Stop on store 0600) 
.8:0301  8D 00 06    STA $0600      - A:FF X:06 Y:FF SP:45 ..-..I.C    2757166
(8:$0304) 

The watchpoint is triggered at intervals of many thousands of cycles and sometimes even garbage instructions (EOR $06) are displayed.

Tested in r46036.