> Also the call to INT67/3F was also commented out just temporarily
> and reactivated later. It's a feature!!! :)
As this means "you temporarily locked the real and virtual A20
to on", and as you call it a "feature", I have two comments...
1. toggling the virtual A20 by remapping a few pages is quite fast
(although having 2 copies of the page table for the first 4 MB
around might be even faster, yet slower during other mapping
updates as 2 copies have to be updated...)
2. if you have no EXEPACKed programs, or if you always use LOADFIX
for them, then yes, one could gain a little bit of speed by
locking the real and virtual A20 to on, in other words, by
skipping the int 67.3f calls.
In summary, I would say it might be nice to have a command
line option "lock a20 to on" for emm386, for example after
FreeDOS 1.0 is done. You should do some benchmarks on a slow
386sx PC in the meantime ;-). By the way, it also might be
nice to have an option "turn a20 on now and then lock it"
for HIMEM as well. I think Tom once supported such an option.
Eric
PS: Normally, only DOS disables the a20, and only when a
program starts. It then enables the a20 again as soon as
the HMA is needed again. So it is not switched often anyway.
If DOS -knew- that you locked the a20 to on, DOS could skip
the "check if a20 is on" each time before it jumps to HMA.
But there is no interface for that in the DOS kernel.
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