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Starting work on disambiguating PCjs the emulator from PCjs the project/website; the emulator will become PCx86

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This commit is contained in:
Jeff Parsons 2016-05-16 20:53:57 -07:00
commit 288f28055d
1519 changed files with 16242 additions and 6939 deletions
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14
_posts/2015-04-16-compaq-deskpro-386-update.md
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@ -5,22 +5,22 @@ date: 2015-04-16 11:00:00
category: 80386
permalink: /blog/2015/04/16/
machines:
- type: pc
- type: pcx86
id: deskpro386
debugger: true
uncompiled: true
config: /devices/pc/machine/compaq/deskpro386/ega/2048kb/debugger/machine.xml
config: /devices/pcx86/machine/compaq/deskpro386/ega/2048kb/debugger/machine.xml
---
PCjs can now boot the [COMPAQ DeskPro 386/16 ROM BIOS](/devices/pc/rom/compaq/deskpro386/).
PCx86 can now boot the [COMPAQ DeskPro 386/16 ROM BIOS](/devices/pcx86/rom/compaq/deskpro386/).
There's still a problem with the hard disk controller, which I haven't looked into yet,
but booting from a floppy works.
While working through issues with this ROM BIOS, I created some lightly-annotated
[source code](/devices/pc/rom/compaq/deskpro386/1988-01-28/1988-01-28.asm) that can be re-assembled
[source code](/devices/pcx86/rom/compaq/deskpro386/1988-01-28/1988-01-28.asm) that can be re-assembled
with [NASM](http://www.nasm.us/). The initial process of creating the source code is
explained [here](/devices/pc/rom/compaq/deskpro386/#recreating-rom-source-code).
explained [here](/devices/pcx86/rom/compaq/deskpro386/#recreating-rom-source-code).
At the top of the source code, I explain a few important details about ROM addresses that
are worth recapping here:
@ -129,7 +129,7 @@ protected-mode with A20 disabled -- an unwise thing to do on most machines:
mov cr0,eax ; 0000F4A4 0F2200
jmp 0x28:xf4ac ; 0000F4A7 EAACF42800
Before fully understanding the DeskPro's unusual A20 management, PCjs worked around it by
Before fully understanding the DeskPro's unusual A20 management, PCx86 worked around it by
redirecting all A20 changes from the Bus component to the CPU component, giving the CPU first
crack at any changes to A20. If the CPU was in real-mode, it would simply pass the A20 request
on to the Bus. However, if the CPU was in protected-mode, it would maintain the requested
@ -143,7 +143,7 @@ to match that of the 1st megabyte whenever A20 is disabled. I could probably ge
only the first 64Kb of the 2nd megabyte, but until I'm actually able to run some tests on a real
DeskPro 386, I'm going to assume COMPAQ's A20 implementation affected the entire 2nd megabyte.
Here's my [COMPAQ DeskPro 386/16](/devices/pc/machine/compaq/deskpro386/ega/2048kb/debugger/) test
Here's my [COMPAQ DeskPro 386/16](/devices/pcx86/machine/compaq/deskpro386/ega/2048kb/debugger/) test
configuration. Set a breakpoint at F000:F498 ("bp f000:f498") in the Debugger panel to see the above
code in action. When the machine is operating in real-mode, you can use the "rp" command to dump all
the registers, including the current base and limit values loaded into the segment registers.