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Index > DOS > How to perform I/O with "use32"

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HeadCase



Joined: 08 Jul 2008
Posts: 3
Location: United Kingdom
HeadCase
Hi,

I have recently started using FASMD, and managed to develop a reasonably good prime number finder with the "use16" directive, where I use int 21h/xxh to perform I/O to the console.

I would now like to explore the use of 32-bit instructions and data by changing the prime number program to test for primes up to 4 billion.

What I would like to know is:

How do I perform simple I/O, like int 21h/xxh, when using 32-bit instructions (i.e. replacing "use16" with "use32")?

It might help you to formulate a reply if I state that I AM a former 16-bit assembler programmer but my knowledge is phenominally out of date, plus I know nothing about DPMI but the name.

Thanks in advance....

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Post 08 Jul 2008, 14:31
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17269
Location: In your JS exploiting you and your system
revolution
If you are using DOS then you have to find a way to switch the CPU into 32bit mode before you can use use32. DMPI (and similar) may be a good way to start. The DOS version of fasm can use DMPI, have a look at "modes32.inc".
Post 08 Jul 2008, 15:07
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LocoDelAssembly
Your code has a bug


Joined: 06 May 2005
Posts: 4633
Location: Argentina
LocoDelAssembly
Quote:

I would now like to explore the use of 32-bit instructions and data by changing the prime number program to test for primes up to 4 billion.


But, do you really need more memory? You could just write the 32-bit instructions straight without trouble, the penalty will be that each instruction will take extra space (for the override prefixes) and maybe a little more time to execute.
Post 08 Jul 2008, 15:37
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HeadCase



Joined: 08 Jul 2008
Posts: 3
Location: United Kingdom
HeadCase
Hi Revolution and Loco,

Thanks for your replies. Perhaps I haven't explained the situation very well. Let me try again...

I've attached the whole program that I would like to change to find primes to 4 billion.

Is it simply a case of me using DX:AX register pair to perform calculations or do I need to recode as a 32-bit program?


Description:
Download
Filename: New Text Document.txt
Filesize: 18.21 KB
Downloaded: 60 Time(s)


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Post 08 Jul 2008, 16:35
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f0dder



Joined: 19 Feb 2004
Posts: 3170
Location: Denmark
f0dder
HeadCase: you can use 32bit registers from 16bit apps, you just can't use 32bit addressing.

Anyway, I'd suggest you take a look at either japheth's HX dos extender, or the old WDOSX extender - those make it easy to write 32bit dos executable, including memory access etc.
Post 08 Jul 2008, 17:23
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LocoDelAssembly
Your code has a bug


Joined: 06 May 2005
Posts: 4633
Location: Argentina
LocoDelAssembly
Quote:

you just can't use 32bit addressing.

In fact you can but make sure you don't cross the 64KB offset limit with the final calculated address.

Code:
org $100

  mov ah, $09
  mov ebx, table
  mov ecx, -6

  .loop:
    mov dx, [ebx+ecx*2+12]
    int $21

    inc cx
    jnz .loop

  xor ax, ax
  int $16

  int $20


struc Table [string] {
common
  .:
forward
local ..entry
  dw ..entry
forward
  ..entry db string, '$'
}

table Table '1', '2', '3', '4', '5', '6'    
Post 08 Jul 2008, 17:37
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roboman



Joined: 03 Dec 2006
Posts: 122
Location: USA
roboman
jezzzzz Dex hasn't chimed in yet !! You could use DexOS Smile
Post 10 Jul 2008, 03:03
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17269
Location: In your JS exploiting you and your system
revolution
roboman wrote:
jezzzzz Dex hasn't chimed in yet !! You could use DexOS Smile
DexOS is not an extension for DOS.
Post 10 Jul 2008, 04:20
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DOS386



Joined: 08 Dec 2006
Posts: 1901
DOS386
Quote:
I have recently started using FASMD


wow ... the 2nd one Laughing

Quote:
and managed to develop a reasonably good prime number finder with the "use16" directive, where I use int 21h/xxh to perform I/O to the console


Smile

Quote:
I would now like to explore the use of 32-bit instructions and data by changing the prime number program to test for primes up to 4 billion


32-bit instructions indeed do work to some degree in 16-bit RM also ... but better to use DPMI. RTFF ! (FAQ on subforum top) Very Happy Or look at some of my examples.

http://board.flatassembler.net/topic.php?t=8670

Quote:
New Text Document.txt


I wonder whether ^^^ you use DOS at all ...

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Bug Nr.: 12345

Title: Hello World program compiles to 100 KB !!!

Status: Closed: NOT a Bug
Post 11 Jul 2008, 07:49
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HeadCase



Joined: 08 Jul 2008
Posts: 3
Location: United Kingdom
HeadCase
To all who helped with my problem:

I've managed to get my program to calculate primes to above 4 billion - Thanks.

Still have a great deal to learn though. It's obvious from the level of my question that I know very little about the x86 and the various assemblers able to be used on it. I do, however, intend to learn much more about them and you've helped me in the first steps along a very long road.

Thanks again, and keep smilin'...

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Post 11 Jul 2008, 13:11
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