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edfed



Joined: 20 Feb 2006
Posts: 4237
Location: 2018
edfed
boot sector is on floppy or else, the rest is on USB pen at a random location.
Is it possible within 460 bytes to code a int13 equivalent for USB pen? 50 restant are for int13-based bootloader, the 2 last ones are for boot mark 0AA55h
Post 18 Dec 2007, 02:28
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Dex4u



Joined: 08 Feb 2005
Posts: 1601
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Dex4u
Yes and no, to boot from usb pen, you need to emulate floppy or hdd (so you can use int 13h for that).
But you can not boot from floppy and then load from usb pen drive, without removing the floppy and rebooting.
Post 18 Dec 2007, 18:46
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edfed



Joined: 20 Feb 2006
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edfed
Quote:

but you cannot boot from floppy and then load from usb pen drive, without removing the floppy and reboot

why?
Grub is able to load different bootloaders...
To reload a boot, simply load it at seg:7C00h and jump to this location, the problem is:
it is possible to read a usb pen with a PIO function less than 460 bytes?
if possible , where to find the documents, reading usb pen with pio.
Post 18 Dec 2007, 21:41
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f0dder



Joined: 19 Feb 2004
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f0dder
Dex4u wrote:
Yes and no, to boot from usb pen, you need to emulate floppy or hdd (so you can use int 13h for that).
But you can not boot from floppy and then load from usb pen drive, without removing the floppy and rebooting.


Sure you can, if you program the USB pendrive directly, instead of relying on BIOS floppy emulation.

What's the obsession with 512 byte bootsector anyway, there's plenty more room on a floppy than just the bootsector...

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Post 18 Dec 2007, 23:51
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Dex4u



Joined: 08 Feb 2005
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Dex4u
f0dder wrote:
Dex4u wrote:
Yes and no, to boot from usb pen, you need to emulate floppy or hdd (so you can use int 13h for that).
But you can not boot from floppy and then load from usb pen drive, without removing the floppy and rebooting.


Sure you can, if you program the USB pendrive directly, instead of relying on BIOS floppy emulation.

What's the obsession with 512 byte bootsector anyway, there's plenty more room on a floppy than just the bootsector...


No you can not, the only way is to use emulation, or code a usb stack, not likely in 460 bytes.
You must be living in dream land, Why do you need to add a USB stack to Dos, if you can read/write to it using pio or int 13h ?, The simple answer is, you can not without emulation and by booting from it (or coding a USB stack ).
Once you boot from it, you can use emulation in realmode, but it stops if you go to pmode.

Theres a small chance of it working, if maybe you have no hdd installed.
Post 19 Dec 2007, 01:46
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edfed



Joined: 20 Feb 2006
Posts: 4237
Location: 2018
edfed
in fact, i have some problems with floppies, as i don't want to buy new ones, i use some dead floppies, only the boot sector is good, the rest is bad.
i cannot boot from usb pen on my machines, but i can from floppy

why emulation? i don't see what you mean by emulation.

i just want to read the content of the memory chip on the usb drive and you speak about emulation. it's strange...

i don't want a dos dependant usb pen driver
do you understand?
i spoke about int13h and PIO as exemple, not as restrictions.

Code:
mov dx,usb_drive_IO
in eax,dx 
;that's all i want.
    
Post 19 Dec 2007, 02:16
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Dex4u



Joined: 08 Feb 2005
Posts: 1601
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Dex4u
edfed wrote:

i cannot boot from usb pen on my machines, but i can from floppy
why emulation? i don't see what you mean by emulation.
i just want to read the content of the memory chip on the usb drive and you speak about emulation. it's strange...
i don't want a dos dependant usb pen driver
do you understand?
i spoke about int13h and PIO as exemple, not as restrictions.

edfed my dear chap, because you want a easy way, does not mean there is one.
USB are one of the hardest device to code for, why do you think LINUX had a problem.
You can write a USB stack (alot of work), but in your case you can not use any other way (as you can not boot usb )
Emulation is away to use usb, by tricking the boot loader into thinking its loading from a floppy or hdd using int 13h, but your BIOS need to be able to do that, yours can not.

Your best loading from a normal hdd.

Note: I have done a lot of work with USB, i am working on a USB stack for DexOS right now, 5 months and i only have the basic's done.


Last edited by Dex4u on 19 Dec 2007, 02:39; edited 1 time in total
Post 19 Dec 2007, 02:38
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LocoDelAssembly
Your code has a bug


Joined: 06 May 2005
Posts: 4633
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LocoDelAssembly
edfed, by emulation they mean BIOS emulation, like "El Torito" does. When you use the INT13, the BIOS will fool your boot code making it beleave that the pen is either a HDD, a Floppy or a CDROM (and maybe some other types of emulation exists).

http://www.ctyme.com/intr/int-13.htm <- Check from Int 13/AH=4Ah to see somewhat related stuff
Post 19 Dec 2007, 02:39
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sinsi



Joined: 10 Aug 2007
Posts: 693
Location: Adelaide
sinsi
edfed wrote:

Code:
mov dx,usb_drive_IO
in eax,dx 
;that's all i want.
    

Heh, if only it was that easy.

Look here for a DOS USB driver http://www.dosusb.net/
Post 19 Dec 2007, 02:40
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edfed



Joined: 20 Feb 2006
Posts: 4237
Location: 2018
edfed
i understand now.
i'll use the first 4kbyte of my hdd ( unsused by FAT32 )
it's sufficient for the moment.
thanks
i'll wait your code as exemple.
Post 19 Dec 2007, 02:41
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edfed



Joined: 20 Feb 2006
Posts: 4237
Location: 2018
edfed
so if i well understand, usb drive need a lot of routines to works. ok.

aïe aïe äïe
headacke
Post 19 Dec 2007, 02:44
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f0dder



Joined: 19 Feb 2004
Posts: 3170
Location: Denmark
f0dder
Dex4u wrote:
f0dder wrote:
Dex4u wrote:
Yes and no, to boot from usb pen, you need to emulate floppy or hdd (so you can use int 13h for that).
But you can not boot from floppy and then load from usb pen drive, without removing the floppy and rebooting.


Sure you can, if you program the USB pendrive directly, instead of relying on BIOS floppy emulation.

What's the obsession with 512 byte bootsector anyway, there's plenty more room on a floppy than just the bootsector...


No you can not, the only way is to use emulation, or code a usb stack, not likely in 460 bytes.
You must be living in dream land, Why do you need to add a USB stack to Dos, if you can read/write to it using pio or int 13h ?, The simple answer is, you can not without emulation and by booting from it (or coding a USB stack ).
Once you boot from it, you can use emulation in realmode, but it stops if you go to pmode.

Theres a small chance of it working, if maybe you have no hdd installed.


Re-read my post?

Writing a USB stack is what I meant, and hence also why I asked about the bootsector-size obsession, because obviously you can't fit an USB stack in 460 bytes.

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Post 19 Dec 2007, 12:09
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moile



Joined: 04 Feb 2005
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moile
and is it possible to write it within 8 sectors?
this is the maximum of contiguous good sectors i have on my floppies!
Post 19 Dec 2007, 21:00
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