Ouch. Adding V8086 mode is *not* pretty. It adds plenty of overhead, is
the cause of too many bugs (thunking between protected and v8086 isn't a
ride in the country), and considering that we're not going to have DOS
compatibility with JOS, isn't worth it.
Unfortunately, this also means that if there's anything in real mode memory
that you want, it needs to be protected before we switch over to protected
mode. Otherwise, we might overwrite that memory.
I remember when I was doing boot-sector research, I found that OS/2's boot
loader copies the fixed disk table into a high area of memory so that it
will be saved when the protected mode kicks in. I doubt that this is very
feasable for us, considering that we're using COTS boot loaders. So we'll
probably have to load VGA fonts on our own.
-Matt
----- Original Message -----
From: Hilary Cheng <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Tuesday, September 07, 1999 7:39 PM
Subject: Re: [JOS-Kernel] decaf updates
Hi Ranieri,
I have think about it. I concern about Real Mode Interrupt. Since JJOS
is running under Protected Mode.
As I know, most of the real mode interrupt will not work under protected
mode. If JJOS can provide a Real
Mode Interface, we could save lots of times.
Regards,
Hilary
----- Original Message -----
From: Ranieri Argentini
To: [EMAIL PROTECTED]
Sent: 26 August 1999 PM 22:14
Subject: Re: [JOS-Kernel] decaf updates
>>cool, do you read the fonts from the vid-mem? the start routine
>>clears unforunately the hole vid-mem, so no fonts after the stop routine
>>are available (yet).
>
>well, I just copy the font from Linux and store in byte array. and draw
it
>pixel on the screen. I think that would be much more easy to do it.
>hm, What's vid-mem ? :o, I remember that font are stored in VGA.
>But I forget how to retrieve it from VGA. is there any Doc?
This is the way to retrieve it using the BIOS. This might prove to be a
bit problematic in OS design, but solving this problem is left as an
excersize for the reader ;-D
This info has been extracted from Ralf Brown's interrupt list, file
inter60a.zip available through ftpsearch.lycos.com ....
Hope it helps someone somewhere ...
Ranieri
--------V-101130-----------------------------
INT 10 - VIDEO - GET FONT INFORMATION (EGA, MCGA, VGA)
AX = 1130h
BH = pointer specifier
00h INT 1Fh pointer
01h INT 43h pointer
02h ROM 8x14 character font pointer
03h ROM 8x8 double dot font pointer
04h ROM 8x8 double dot font (high 128 characters)
05h ROM alpha alternate (9 by 14) pointer (EGA,VGA)
06h ROM 8x16 font (MCGA, VGA)
07h ROM alternate 9x16 font (VGA only) (see #00021)
11h (UltraVision v2+) 8x20 font (VGA) or 8x19 font (autosync
EGA)
12h (UltraVision v2+) 8x10 font (VGA) or 8x11 font (autosync
EGA)
Return: ES:BP = specified pointer
CX = bytes/character of on-screen font (not the requested
font!)
DL = highest character row on screen
Note: for UltraVision v2+, the 9xN alternate fonts follow the
corresponding
8xN font at ES:BP+256N
BUG: the IBM EGA and some other EGA cards return in DL the number of
rows on
screen rather than the highest row number (which is one less).
SeeAlso: AX=1100h,AX=1103h,AX=1120h,INT 1F"SYSTEM DATA",INT 43"VIDEO DATA"
Format of alternate font table [array]:
Offset Size Description (Table 00021)
00h BYTE character to be replaced (00h = end of table)
01h N BYTEs graphics data for character, one byte per scan line
--------V-101130BX4D4F-----------------------
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