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FreeDOS on SBC188 (Announce)

posted by GizMo79, 14.09.2020, 21:46

> > > > > By the way, how much memory is installed on this system and
> > available
> > > to
> > > > > DOS?
> > > >
> > > > 1Mb
> > >
> > > It is unlikely that the entire MiB is available to DOS, which expects
> at
> > > most 640 KiB generally. (It can be higher, but not a full MiB.) Try
> > running
> > > ldebug /C="a;int 12;;t;h ax * #1024;q" (You can use the
> > > executable in the second archive I posted.)
> >
> > [image]
>
> As expected there's 640 KiB of low memory available to DOS. It is highly
> likely that this is the same as available to the dot-displaying boot sector
> loader, which means that a lack of memory is not a cause for its failure.
>
> By the way, it might be possible to have a special driver offer some
> additional memory (between 640 KiB and 1024 KiB) to DOS as upper memory. If
> so then your DOS=UMB setting could take effect and DOS could link such
> memory as UMBs into its memory chain.
>
> Perhaps such a driver already exists for the SBC188. I created
> such
> a driver for the 8086tiny environment. However, it would have to be
> adjusted to work with the SBC188. And it would be crucial to know exactly
> which memory areas are both backed by actual RAM and available for us to
> use. As I stated
> in
> the readme: "the UMB area is assumed by the DOS driver. (This is 128
> KiB (2000h paragraphs) between segments D000h and EFFFh.)"
how do i know these things? i don't know exactly how SBC188's RAM is mapped,
is there any way to find out? however with ms dos 6.22 the ram occupied was only 60k (command.com) freedos consumes almost 140k

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