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Jemm 5.77 (Announce)

posted by Japheth Homepage, Germany (South), 20.06.2012, 15:14

Hello,

again an update of jemm:

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- commandline option I=A000-B7FF didn't increase DOS low memory, the
region became just the first UMB.
- tool MOVEXBDA added.
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about including A000:
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รพ The I=XXXX commandline option may be used to include the VGA "graphics"
segment A000h. It might be possible to increase DOS conventional memory
up to 736 kB by option I=A000-B7FF. However, there are quite a few
hurdles that may cause unexpected results:
- conventional memory is increased only if the region to include is
adjacent to current memory. On newer machines, there's very often a
"hole", caused by the Extended BIOS Data Area (XBDA or EBDA); thus
the included region just becomes an UMB and won't increase lower memory.
Use tool MOVEXBDA to fix this issue!
- Once address space A000h is remapped, any attempts to run programs that
use VGA graphics most likely with cause a crash.
- Depending on the VGA-BIOS it may happen that some non-graphics functions
won't work anymore and may also cause a crash. In the worst case, it's
not even possible to set a video text mode.
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About MOVEXBDA:
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MOVEXBDA is a device driver supposed to move the Extended BIOS Data
Area ( XBDA or EBDA ) to low DOS memory. If an XBDA exists, it is usually
located just below the A000 video segment, with a size of 1 or 2 kB.
Moving the XBDA to low memory allows Jemm to increase DOS low memory up to
736 kB with commandline parameter I=A000-B7FF ( one should be aware of a
few limitations of this setting - see below for more details ).

Some DOS versions will move the XBDA on their own; then MOVEXBDA is not
needed and will do nothing if launched.

MOVEXBDA should work with other EMMs as well. Brief tests with MS Emm386
didn't reveal any problems. However, it looks like MOVEXBDA won't work
reliably with FreeDOS!
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XCDROM32 also got a few updates, all related to "play audio" device driver functions. These changes were the result of a "teamplay" with J.R. Ellis. Thanks!

http://www.japheth.de/Jemm.html

---
MS-DOS forever!

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