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James Gregory 2013-12-31 17:12:29 +11:00
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@ -46,17 +46,17 @@ discussed in the next chapter.
### A Brief Note on Word OUTs {#Heading9}
In the early days of the EGA and VGA, there was considerable debate
about whether it was safe to do word **OUT**s (**OUT DX,AX**) to set
about whether it was safe to do word `OUT`s (`OUT DX,AX`) to set
Index/Data register pairs in a single instruction. Long ago, there were
a few computers with buses that weren't quite PC-compatatible, in that
the two bytes in each word **OUT** went to the VGA in the wrong order:
the two bytes in each word `OUT` went to the VGA in the wrong order:
Data register first, then Index register, with predictably disastrous
results. Consequently, I generally wrote my code in those days to use
two 8-bit **OUT**s to set indexed registers. Later on, I made it a habit
to use macros that could do either one 16-bit **OUT** or two 8-bit
**OUT**s, depending on how I chose to assemble the code, and in fact
you'll find both ways of dealing with **OUT**s sprinkled through the
two 8-bit `OUT`s to set indexed registers. Later on, I made it a habit
to use macros that could do either one 16-bit `OUT` or two 8-bit
`OUT`s, depending on how I chose to assemble the code, and in fact
you'll find both ways of dealing with `OUT`s sprinkled through the
code in this part of the book. Using macros for word OUTs is still not a
bad idea in that it does no harm, but in my opinion it's no longer
necessary. Word **OUT**s are standard now, and it's been a long time
necessary. Word `OUT`s are standard now, and it's been a long time
since I've heard of them causing any problems.