From:	"Florian Xaver" <dos DOT fire AT aon DOT at>
To:	<djgpp AT delorie DOT com>
Subject:	Re: PMode stuff
Date:	Sat, 10 Jun 2000 18:17:26 +0200
Message-ID:	<01bfd2f7$5e52c120$d15ab7d4@default>
MIME-Version:	1.0
X-Priority:	3
X-MSMail-Priority:	Normal
X-Mailer:	Microsoft Outlook Express 4.71.1712.3
X-MimeOLE:	Produced By Microsoft MimeOLE V4.71.1712.3
Reply-To:	djgpp AT delorie DOT com

Hi!

I read your posting at the djgpp mailing list and it sounds very nice.
Your homepage is very good too!!!

Maybe you could help the FreeDOS project?
It need such developers like you!
:-)

Bye, Florian

FreeDOS
(English) http://www.freedos.org
(German) http://members.tripod.de/FreeDOS/
Seal -  free desktop enviroment for DOS
http://www.seal.de.vu
DrDOS/OpenDOS
http://www.drdos.org

-----Ursprungliche Nachricht-----
Von: Alexei A. Frounze <alex DOT fru AT mtu-net DOT ru>
Newsgroups: comp.os.msdos.djgpp
An: Prashant TR <prashant_tr AT yahoo DOT com>
Cc: djgpp AT delorie DOT com <djgpp AT delorie DOT com>
Datum: Samstag, 10. Juni 2000 17:16
Betreff: PMode stuff


>Hello Prashant!
>
>I've just read your html doc about PMode and realized to come up with a
>suggestion.
>First, general information and advantages of PMode are described quite well
>in your doc.
>
>If you're really good at PMode and you're going to keep on continuing this
>doc in details, I'd like to work on it in cooperation with you.
>
>I think we can cooperate your English skills and my real PMode knowlege (I
>know nothing about yours, please forgive me :).
>I'm writing PMode tutorials.
>They are mix of C and ASM (maximum C, minimum ASM). And they're being done
>with such free compilers as Turbo C 2.01 and NASM 0.98.
>
>Right now I've finished 15 tutorials... Two weeks of job. But I have to
>provide a good documentation. A month minimum for me. :)) So why don't we
do
>this stuff much cooler and more practical: doc + example programs?
>
>Here goes a list of ready-made tutorials with some comments:
>
>TUT01   Switches to PMode and back to real mode using CR0. On startup CPU
>        mode is checked using SMSW instruction. Bit 0 equals 0, if real
mode
>        and 1, if PMode/V86. This is done to avoid conflicts with EMM386
and
>        similar drivers and Windows.
>
>TUT02   Sets up GDT, goes to PMode, prints "Hello from PMode!" and goes
>back.
>
>TUT03   The same GDT as before, IDT is setup for software ISR (Int 20h) and
>        divide by zero exception (Int 0). Tut shows work of these handlers.
>        Note, these handlers are defined as 286 ones (see ACS_INT_GATE in
>the
>        PM_DEFS.H file).
>
>TUT04   The same GDT as before, IDT is setup for all exceptions,
>        you may now see type and address of an exception. Try different
>        exceptions and see what's going on.
>        Note, all handlers are defined as 386 ones now.
>        Note #2: since all exception handler wrappers call one common
>        exception handler and there is no additional stack provided, stack
>        faults are not handled properly. Basically such a design is good
>        for GPFs, TSS exception and similar things.
>
>TUT05   The same GDT as before, almost the same IDT as in TUT04. Two IDT
>        entries and IRQ handlers are added -- IRQ0 (timer) and
>        IRQ1 (keyboard). The tut reprograms PIC in order to handle IRQs
>        in PMode.
>
>TUT06   Almost the same as TUT05. Task switching is added. main() switches
>        to task() using a jump to TSS. Then task() waits for the ESC key.
>        After ESC, task() switches back to main(). Both tasks are PL#0.
>        Note, for such PL#0 tasks I/O map is not needed in TSS. Since there
>        are only PL#0 tasks, there is no need to setup stacks for
interlevel
>        calls (SS0:ESP0,SS1:ESP1,SS2:ESP2).
>
>TUT07   Multitasking again. 3 PL#0 tasks (main(), task1(), task2()) work
>now.
>        Task switches are scheduled by a scheduler called from timer IRQ
>ISR.
>        I.e. preemptive multitasking.
>
>TUT08   Demo of page translation. The demo shows 16 color bars in 3 cases:
>        1. page translation disabled (linear addresses equal physical ones)
>           Bars are drawn in the black, blue, ... yellow, white order
>        2. page translation enabled (linear addresses equal physical ones)
>           Bars are drawn in the black, blue, ... yellow, white order
>        3. page translation enabled (linear addresses don't equal
physicals)
>           Bars are drawn in the opposite order:
white,yellow,...,blue,black
>
>TUT09   Back to preemptive multitasking... :-) This tutorial is a bit
>        different to TUT07. It doesn't use TSS for task switchings now.
>        It uses stack-based switching instead. People say it's faster than
>        TSS-based method. Dunno, perhaps they're correct. MS Windows
>        uses this stuff a lot. Btw, this method also applicable to almost
>any
>        CPU. Even PC/XT made on 8086/8088 CPUs could have such task
>        switching. ;-)
>
>TUT10   Well, let's have a rest. :-) This tutorial shows Big/Unreal Mode,
>        i.e. accessing RAM in real mode with use of just a 32-bit offset.
>        Yeah, it's really possible. In fact, you may access up to 4GB
>        of RAM from Real mode this way.
>
>TUT11   It's almost the same as TUT07. The only difference is that task1()
>        and task2() tasks are 32-bit (32-bit code segments with 32-bit
>        instructions) and these tasks are in privilege level 3, IOPL=3 too.
>        New GDT entires added for PL#3 code and data segments respectively.
>        Screen segment is also redefined as PL#3.
>
>TUT12   The same as TUT11. 2 LDTs are added for each PL#3 task.
>
>TUT13   Multitasking. First time we run a Virtual 8086 machine here.
>
>TUT14   Advanced V86 stuff. A software Int nn is now supported for V86
>tasks.
>
>TUT15   A working V86 monitor. It redirects IRQs to the V86 task now. So we
>        have our DOS stuff in V86 mode just like DOS-box in Windows.
>
>
>Bye.
>Alexei A. Frounze
>-----------------------------------------
>Homepage: http://alexfru.chat.ru
>Mirror:   http://members.xoom.com/alexfru
>

- Raw text -