Misc/abrash-black-book
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Change bold code snippets to inline code blocks

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James Gregory 2013-12-31 17:12:29 +11:00
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18
03-08.md
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@ -15,25 +15,25 @@ approach could conceivably cause erratic 8253 operation, which could in
turn seriously affect your computer's operation until the next reboot.
In non-8253-compatible systems, I've observed not only wildly incorrect
timing results, but also failure of a diskette drive to operate properly
after the long-period Zen timer with **PS2** set to 0 has run, so be
alert for signs of trouble if you do set **PS2** to 0.
after the long-period Zen timer with `PS2` set to 0 has run, so be
alert for signs of trouble if you do set `PS2` to 0.
Rebooting should clear up any timer-related problems of the sort
described above. (This gives us another reason to reboot at the end of
each code-timing session.) You should *immediately* reboot and set the
**PS2** equate to 1 if you get erratic or obviously incorrect results
with the long-period Zen timer when **PS2** is set to 0. If you want to
set **PS2** to 0, it would be a good idea to time a few of the listings
in this book with **PS2** set first to 1 and then to 0, to make sure
`PS2` equate to 1 if you get erratic or obviously incorrect results
with the long-period Zen timer when `PS2` is set to 0. If you want to
set `PS2` to 0, it would be a good idea to time a few of the listings
in this book with `PS2` set first to 1 and then to 0, to make sure
that the results match. If they're consistently different, you should
set **PS2** to 1.
set `PS2` to 1.
While the the non-PS/2 version is more dangerous than the PS/2 version,
it also produces more accurate results when it does work. If you have a
non-PS/2 PC-compatible computer, the choice between the two timing
approaches is yours.
If you do leave the **PS2** equate at 1 in Listing 3.5, you should
If you do leave the `PS2` equate at 1 in Listing 3.5, you should
repeat each code-timing run several times before relying on the results
to be accurate to more than 54 ms, since variations may result from the
possible lack of synchronization between the timer 0 count and the BIOS
@ -58,7 +58,7 @@ all you have to do is link in the long-period timer instead.
Listing 3.6 shows a test-bed program for the long-period Zen timer.
While this program is similar to Listing 3.2, it's worth noting that
Listing 3.6 waits for a few seconds before calling **ZTimerOn**, thereby
Listing 3.6 waits for a few seconds before calling `ZTimerOn`, thereby
allowing any pending keyboard interrupts to be processed. Since
interrupts must be left on in order to time periods longer than 54 ms,
the interrupts generated by keystrokes (including the upstroke of the