Write string (EGA+, meaning PC AT minimum)
AH=13h
AL = Write mode, BH = Page Number, BL = Color, CX = String length, DH = Row, DL = Column, ES:BP = Offset of string

Quick Review: You dont know the content of DS when Executing.
Insert..
Push cs
Pop DS
..at the beginning

hmmm, no luck so far with neither variants. I will keep on trying

Predator99 wrote:

Quick Review: You dont know the content of DS when Executing. Insert.. Push cs Pop DS ..at the beginning […]
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Quick Review: You dont know the content of DS when Executing.
Insert..
Push cs
Pop DS
..at the beginning

are you gauranteed any valid stack either?

I'd do (unless your ss:sp is setup by bios to be safe)

1;; set stack to known position
2xor ax,ax
3mov ss,ax
4mov sp,0x1000
5
6push cs
7push cs
8pop ds
9pop es

your

1mov vpage,bh

where is DS, your in rom, where have you got your variables pointed to? when bios boots, screen resets, so you know your displaypage is always going to be 0!

Why are you censoring parts of a bios boot screen?

BloodyCactus wrote:

are you gauranteed any valid stack either? […]
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Predator99 wrote:

Quick Review: You dont know the content of DS when Executing. Insert.. Push cs Pop DS ..at the beginning […]
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Quick Review: You dont know the content of DS when Executing.
Insert..
Push cs
Pop DS
..at the beginning

are you gauranteed any valid stack either?

I'd do (unless your ss:sp is setup by bios to be safe)

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1;; set stack to known position
2xor ax,ax
3mov ss,ax
4mov sp,0x1000
5
6push cs
7push cs
8pop ds
9pop es

Yes, that a good idea. Was using my mobile yesterday I didnt want to make it too complicated 😉 But usally, SS/SP should already have a valid value as the stack was also used by the prevoius ROM.
You can set SS to 1000 as DOS is not loaded yet.

For debugging under DOS, its also a good idea to to change the initial CS:IP (xxxx:0100?) to something else (e.g. xxxx:0500) and also to set the DS/ES/SS to random values as you cannot rely on anything when its executed in the BIOS.

awgamer wrote:

Why are you censoring parts of a bios boot screen?

It's probably his real name, the part he covered is not part of the boot screen but a message that the executable displays.

sorry but I still don't get it (its always one)... real simple example

1P8086
2MODEL TINY
3ORG 0     ;for BIOS must be 0
4DATASE
5msg db 'Assembled'
6CODESEG
7STARTUPCODE:
8db 55h,0AAh,1	;BIOS
9mov si, offset[msg] <<<
10mov ah,0Eh
11mov al,???<<<
12mov bh,0
13int 10h
14RETF
15END

what I still don't know for sure, if even this is right: mov si, offset[msg] and what exactly I sould put in AL register. Lets start with that.

Well for int10 AH=0xE you need to have in AL the character you want to output.
http://stanislavs.org/helppc/int_10-e.html

I haven't tried doing x86 ROMs before so I would have a couple of questions. Where is the entry point and where is the data section (which contains the string) located in the ROM image?
To write a string to the screen using a BIOS function that outputs one character, maybe you could use a loop like this. (Add a 0 byte to the end of the string to make it null-terminated)

1; routine for writing null-terminated string
2; one character at a time
3mov si, offset[msg]
4looppoint:
5lodsb
6jz stringdone
7mov ah,0Eh
8mov bh,0
9;push si   ;does si need to be preserved when calling BIOS??
10int 10h
11;pop si
12jmp looppoint
13stringdone:

Why don't you just put the message in the code segment?

1jmp begin
2
3msg db xxx
4
5begin:
6mov ax, cs
7mov ds, ax
8...

The code at the "begin" label demonstrates how to move CS into DS without using the stack, but you will need a proper stack to use interrupts anyway, so you might as well use "push cs" + "pop ds" after the stack was set up correctly.

So far, until my last post I got nothing
the best I did was this

with code:

1P8086          ;select the processor
2MODEL TINY     ;always must be TINY model
3org 0h
4DATASEG
5msg db 'Hello'
6db 0FFh,0FFh,0FFh,0FFh ;for modul of 4096
7db 0FFh,0FFh,0FFh,0FFh ;for modul of 4096
8db 0FFh,101            ;for modul of 4096
9CODESEG
10STARTUPCODE
11db 55h,0AAh,1
12
13xor si,si
14mov dx,0
15loop1:
16mov ah,0Eh
17mov al,es:[SI]
18mov bh,0
19int 10h
20inc SI
21inc dx
22cmp dx,140	
23jbe loop1
24
25mov ah,0Eh
26mov al,219     ;a visual marker to see when loop is done
27mov bh,0
28int 10h
29
30mov ah,0Eh	; \n
31mov al,10
32mov bh,0
33int 10h
34mov ah,0Eh
35mov al,13
36mov bh,0
37int 10h
38
39RETF
40END

but... everytime I try to link a pointer to msg it give me blank characters, no matter if is:
mov SI, offset msg
mov si,[msg]
lea bx,msg/mov si,bx or other variants found on internet, when I try to display it with
mov ah,0Eh
mov al,[si] or mov al,[msg][si] or even mov es:[si]
mov bh,0
int 10h
it give me blanks every time

All this make me wonder, mabye I'm chasing the wrong rabbit:
my rom BIOS extension acts like a harddisk??? and then when executes the program, actually the msg is in RAM memory? And all along this time I tryed to link my pointer so desperately to D000, but was in fact something equivalent like trying to link my pointer to what ever specific cylinder or sector on the harddisk? Mabye this is somewhat right

BloodyCactus wrote:

I'd do (unless your ss:sp is setup by bios to be safe) […]
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I'd do (unless your ss:sp is setup by bios to be safe)

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1;; set stack to known position
2xor ax,ax
3mov ss,ax
4mov sp,0x1000
5
6push cs
7push cs
8pop ds
9pop es

where is DS, your in rom, where have you got your variables pointed to?

K1n9_Duk3 wrote:

Why don't you just put the message in the code segment?
The code at the "begin" label demonstrates how to move CS into DS without using the stack, but you will need a proper stack to use interrupts anyway, so you might as well use "push cs" + "pop ds" after the stack was set up correctly.

What I'm asking afterall, is how this code in rom image behave? like a file on a harddisk? or like an already executed program loaded in to memory (I doubt that because I can modify some variabiles, for example vpage db 0 from my previous posts, the EEPROM cant be burned everytime I change a variabile)

Also about this stack cs/ss/cp, every time I touch them the computer freeze(but I suspect is my fault).

In case you wondering what is in the first pic, is the code from above compiled

32768 wrote:

All this make me wonder, mabye I'm chasing the wrong rabbit:

I see you using ES overrides, but have you actually set ES to your code segment manually? I dont see your coding doing

mov ax,cs
mov es,ax

to actually use it.

32768 wrote:

my rom BIOS extension acts like a harddisk??? and then when executes the program, actually the msg is in RAM memory?

.....

What I'm asking afterall, is how this code in rom image behave? like a file on a harddisk? or like an already executed program loaded in to memory (I doubt that because I can modify some variabiles, for example vpage db 0 from my previous posts, the EEPROM cant be burned everytime I change a variabile)

it behaves as its in a fixed location. You should also try and make it internally relocatable / relative.

1db 0xE8,0,0
2pop bx
3sub bx,4

then you can index from that

1lea si,[bx + msg]

I suspect your vpage variable 'works' in the sense its always 0, so it only _seems_ to work but its in ROM so it can never change, but since the computer boots up in page 0, you never need anything else.

also your header should have an index to the start of your code routine and make sure your CRC adds to zero.

why are you printing 140 characters when your message is 5? just zero terminate your message and detect zero byte.

BloodyCactus wrote:

32768 wrote:

I see you using ES overrides, but have you actually set ES to your code segment manually? I dont see your coding doing mov ax,cs […]
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I see you using ES overrides, but have you actually set ES to your code segment manually? I dont see your coding doing
mov ax,cs
mov es,ax
...
why are you printing 140 characters when your message is 5? just zero terminate your message and detect zero byte.

got home, made the modification...same behaviour
also tried:
mov ax,cs
mov ds,ax
just to be sure, still nothing
as soon I insert this mov si,offset msg all I get is blank characters

That 140 is because my style of debugging, I call it something close in english to crap shooting, before all I got was blank characters, I was probing blindly to see where I'm at

You have org 0 before the data segment but for the option ROM to execute the bytes $55 $AA must be at 0, so it is still unclear where that data segment is really located. Why not move the string to the end of the code segment instead?

1P8086          ;select the processor
2MODEL TINY     ;always must be TINY model
3org 0h
4CODESEG
5STARTUPCODE
6db 55h,0AAh,1
7
8mov ax,cs
9mov ds,ax
10mov es,ax
11
12mov si,offset msg
13mov dx,0
14loop1:
15mov ah,0Eh
16mov al,es:[SI]
17mov bh,0
18int 10h
19inc SI
20inc dx
21cmp dx,140   
22jbe loop1
23
24mov ah,0Eh
25mov al,219     ;a visual marker to see when loop is done
26mov bh,0
27int 10h
28
29mov ah,0Eh   ; \n
30mov al,10
31mov bh,0
32int 10h
33mov ah,0Eh
34mov al,13
35mov bh,0
36int 10h
37
38RETF
39
40msg:
41db 'Hello'
42
43END

bakemono wrote:

You have org 0 before the data segment but for the option ROM to execute the bytes $55 $AA must be at 0, so it is still unclear […]
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You have org 0 before the data segment but for the option ROM to execute the bytes $55 $AA must be at 0, so it is still unclear where that data segment is really located. Why not move the string to the end of the code segment instead?

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1P8086          ;select the processor
2MODEL TINY     ;always must be TINY model
3org 0h
4CODESEG
5STARTUPCODE
6db 55h,0AAh,1
7...
8RETF
9msg:
10db 'Hello'
11END

This code should have worked, many others said so and yet.... it didn't. But I found the bug eventually, was because of this: STARTUPCODE. Everything was wrong with this, until I had the ideea to remove that STARTUPCODE and lo behold my Hello apeared for the first time in almost two months. This STARTUPCODE was a reminent left in my code from an *.com example found in Turbo Pascal. Granted it worked under DOS, I dont think the ppl who made that example think that will become part of a BIOS extension after 20 years
Now evertyhing work, no matter if msg is placed in CODESEG or at the end of the code. Even the AH=13h, AL = Write mode, BH = Page Number, BL = Color, CX = String length, DH = Row, DL = Column, ES:BP = Offset of string worked.

All is fine under the sun