Re: Xi 8088 - The improved version of my XT board

[Sergey <skis...@gmail.com>]

Al,

The Xi board allows mapping some RAM above 640K in 0C0000h - 0EFFFFh
area, providing up to 192 KiB of UMBs. Part of this area might be used
by BIOS extension ROMs or for memory mapped I/O, which limits the
usable space. For example VGA cards normally use 0C0000h-0C7FFFh block
for VGA BIOS.

It is possible to eliminate other ROMs (such as XT-IDE BIOS) by
copying them to the BIOS ROM at 0F0000h-0F7FFFh area (memory above
0F8000h is used by the BIOS itself). This will not only save UMB
blocks, but also the ROM ICs for XT-IDE BIOS (or network boot ROM).

I actually tested the UMB with V1.0 board, using USE!UMBS and DOSMAX:
http://ftp.sunet.se/pub/simtelnet/msdos/memutil/use-umbs.zip
http://ftp.sunet.se/pub/simtelnet/msdos/sysutl/dosmax21.zip

This is pretty cool, as it relocates DOS and related stuff to UMBs,
leaving about 625 KiB of usable lower memory.

Implementing a real EMS (with switchable pages) would require more
components, and I didn't want to over-complicate the design. But an
EMS card is an interesting idea for another project.

Thanks,
Sergey

On Sep 25, 3:09 pm, "..I'd rather be coding ASM!" <uri...@deviate.fi>
wrote:
> On Tue, 25 Sep 2012, Sergey wrote:
> > Good. In this case I'd like to know who else will be interested in
> > making a backplane?
>
> > I'll start a separate thread to discuss this.
>
> I'd be super keen to build one. Some suggestions:
>
>   - ATX holes so it can be bolted to easy to find PC cases
>   - AT and ATX connector
>
> Separate idea.. with the XT v2, is there a way to get 64k EMS to work?
> Wondering if there's a RAM expander anyone's tried from the v1.
>
> Al.
>
> --
>   --
>   Al Boyanich
>   adb -w -P "world> " -k /dev/meta/galaxy/ksyms /dev/god/brain