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Re: [N8VEM: 14722] Re: Xi 8088 - The improved version of my XT board


Hi Sergey,
Interesting. I've an old amstrad 286 I've recently got working again and have been playing with UMB/EMS memory windows in tasm. I also have an Orchid Turbo 286 board I've previously had working in an NCR PC 4i and am dead curious if it'd work in the V1 sergey XT hence the tyre kicking. 

A UMB/EMS board would be *very* nifty.

Thanks. :)

Al.

On Tue, 25 Sep 2012, Sergey wrote:


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





--
 --
 Al Boyanich
 adb -w -P "world> " -k /dev/meta/galaxy/ksyms /dev/god/brain