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v1.19.1: More Windows 95 Setup-related fixes

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Jeff Parsons 2015-08-21 18:12:10 -07:00
commit 0398afab84
30 changed files with 50568 additions and 1846 deletions
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blog/2015/07/17/README.md
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@ -84,7 +84,7 @@ crash, you can dump the instruction history buffer using the Debugger's "dh" com
NOTE: The diskette images contain a pre-release version of Windows 95, as I don't currently have the RTM version on
diskette.
Update for August 13, 2015
August 13, 2015 Update
---
PCjs v1.18.8 has made a little more progress running Windows 95 Setup, but CAB decompression still fails almost
@ -144,7 +144,32 @@ A quick recap of those command prefixes (which you won't see until AFTER you've
80386 Debug register (DR0-DR7) support was recently added, so even WDEB386 read/write breakpoints should work now.
August 21, 2015 Update
---
PCjs v1.19.1 has finally solved a number of nagging bugs. The CAB decompression code itself was running
fine; it would crash after loading a 32-bit value into EAX *and* a timer interrupt occurred. A path
through the interrupt handler was trashing the upper bits of EAX. The culprit: any of the MOV instructions
that move an immediate value into one of the "high" 8-bit registers (AH, BH, CH, or DH). Those instructions
were failing to preserve the upper 16 bits of the entire register. Further proof that the most exasperating
bugs sometimes have the most mundane causes.
Also recently fixed: the annoying VGA video glitch that would occur whenever the mouse was moved, improper
updates to the ACCESSED bit in a selector's descriptor table entry, improper error codes when a selector load
generated a fault, and the RETF instruction's failure to properly restart when the return address referred
to a not-present segment.
The next problem appears to be timer-related. When Windows 95 Setup begins its hardware analysis, it
gets "stuck" in code that's reading and writing timer ports (0x40 and 0x43). Turning on timer port messages
with the `"m port on;m timer on"` Debugger commands reveals that the problem maybe an unsupported timer
command:
chipset.outPort(0x0043,PIT1_CTRL,0xD2) @1847:DD02
PIT1_CTRL: Read-Back command not supported (yet)
To be continued....
[Embedded DeskPro 386](/devices/pc/machine/compaq/deskpro386/vga/4096kb/machine.xml "PCjs:deskpro386::uncompiled:debugger")
*[@jeffpar](http://twitter.com/jeffpar)*
*July 17, 2015*
*July 17, 2015* (updated August 13 and August 21, 2015)