Browsing a harddisk under DOS without using BIOS routines (INT13H) \ VOGONS

Browsing a harddisk under DOS without using BIOS routines (INT13H)

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First post, by Jonas-fr

Posted on 2020-07-14, 19:51

Jonas-fr Offline

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Is there any known DOS utility that doesn't use INT13H to access a disk allowing one to browse its files without said HDD to be seen/declared in the BIOS?

I know for a fact that IDEINFO doesn't depend on the BIOS since it can detect IDE drives by querying the bus directly (this in this case letting one's know about a HDD geometry) and without said HDD being declared in the BIOS. Testdisk also uses its own routines but not on the Win9x/DOS version (it is INT13H dependant). The goal of such an utility will be to be able to access files on the motherboard with a dead battery/broken CMOS circuit. This is more a thought experiment than anything else since one can move the HDD on a functioning mobo but bear with me : )

Such utility would be a nice addon for "the all in one floppy"

Reply 1 of 4, by Jo22

Posted on 2020-07-14, 23:52

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Jonas-fr wrote on 2020-07-14, 19:51:

Is there any known DOS utility that doesn't use INT13H to access a disk allowing one to browse its files without said HDD to be seen/declared in the BIOS?

Well, most DOS programs call DOS int21h to access a disk - which in turn calls int13h mainly..
Some disk utilities like DEFRAG ((MS, Symantec), COMPRESS (PC-Tools) and so on also access the disk directly (by-passing DOS), albeit via int13h..

The only "DOS program" I know of which does access a HDD directly is WfW 3.11 with FastDisk driver.
Once virtual memory (permanent swap file), the HDD driver and the drive cache are all enbabled, WfW is entirely self-reliant.
It will nolonger call DOS or BIOS to do it's work. In this state WfW also will emulate int13h for applications then.

That being said, you might also want to have a look at the attachment..
- It describes how DOS retrieves drive geometry information. 😀

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Reply 2 of 4, by Jonas-fr

Posted on 2020-07-15, 15:43

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Thanks for your insight Jo22, the readme in the zip are quite instructive as I think more and more I'll have to code my way around this particular issue.

Reply 3 of 4, by verysaving

Posted on 2020-07-16, 00:42

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take a look at DMDE

https://dmde.com/download.html

there's a version working in DOS, and you can
select a direct IDE mode when accessing the disk.
It's not properly a browser but a data recovery software,
but it can be uses to view files and supports a lot
of file systems.

To test disk directly even ignoring BIOS you can use
MHDD
https://hddguru.com/software/2005.10.02-MHDD/
or VICTORIA
https://hddguru.com/software/2005.10.03-Victoria/

both excellent programs.

Reply 4 of 4, by Jonas-fr

Posted on 2020-07-16, 12:58

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Thanks verysaving, if it works your username will be well chosen indeed !

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