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Credit to Jose Luis for discovering this bug and bringing it to my attention. The fix is a small patch on top of the patches previously applied from Jon Saxton. See the ZPM3 directory in Sources for more information.
40 lines
1.6 KiB
Plaintext
40 lines
1.6 KiB
Plaintext
RESBDOS3.SPR and BNKBDOS3.SPR have been replaced
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with versions from the Jon Saxton disassembly with
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fixes distribution. The file called zpm3fix.txt
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have been included and details the fixes.
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ZPMLDR has also been updated with the version from
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the Jon Saxton disassembly. However, it has additionally
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been updated to correct an issue that was preventing
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RomWBW from booting under ZPMLDR.
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ZPMLDR has a slightly modified version of the rdSeq
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procedure (compared to CPMLDR). It appears that this
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causes deblocking to be bypassed on the initial disk
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read of CPM3.SYS. As a result, the entire disk sector
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(512 bytes) is read starting at 0x0080. This winds up
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overlaying 0x180 bytes of the start of ZPMLDR.COM causing
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it to fail catastrophically.
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According to the documentation at the top of zpm3ldr.z80,
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zpmldr is normally loaded from system tracks to address
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0x0400. In that scenario, the read of the entire sector
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would not overlay the start of the application. So, I
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suspect this is why this (bug?) is not relevant to many
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implementations.
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The ZPM3LDR.REL file used here has been modified to
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sync the rdSeq procedure back to the DIR CPMLDR version.
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This seems to allow ZPMLDR to work with RomWBW now.
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--WBW 4:22 PM 12/8/2021
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Jose Luis reported that attempting to change to a different
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DU by using a named directory was not working correctly.
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It was working with the original ZPM3 distribution, but not
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with the Jon Saxton patches. Refer to the RomWBW Issue
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https://github.com/wwarthen/RomWBW/issues/324. I was able
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to track down the issue and have applied an additional
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patch to correct the Jon Saxton variant.
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--WBW 8:46 PM 3/12/2023 |