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 Post subject: How to access ALL the mass storage devices through BIOS?
PostPosted: Wed Jan 16, 2019 6:29 am 
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Joined: Wed Jul 27, 2016 5:37 am
Posts: 9
Hi!
E.g. with INT 13, AH=0x42, I can read a mass storage device. The "drive number" of the boot device is provides through DL to the bootstrap code.
But is there a way I can list all the other mass storage devices attached (HDDs, SDDs, USB drives), identify them and get their drive numbers?
It seems like a standard question, but I looked for it, and maybe I was just too stupid to find the answer?
Thank you for your help.


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 Post subject: Re: How to access ALL the mass storage devices through BIOS?
PostPosted: Wed Jan 16, 2019 6:49 am 
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Joined: Mon Mar 25, 2013 7:01 pm
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You can't access all storage devices through the BIOS. You can only access the storage devices the BIOS knows how to access.

You can find out how many of those there are by reading the byte at address 0x475 (in the BDA). Drives are numbered sequentially, starting at 0x80.

After that, you can use whichever INT 0x13 calls you want to identify the drives.


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 Post subject: Re: How to access ALL the mass storage devices through BIOS?
PostPosted: Wed Jan 16, 2019 7:41 am 
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Joined: Wed Oct 18, 2006 3:45 am
Posts: 9287
Location: On the balcony, watching the Swedish Chef
Octocontrabass wrote:
You can only access the storage devices the BIOS knows how to access.
... and then only whatever it is willing to present to you. Expect having just your boot drive and one (other) harddisk.

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"Certainly avoid yourself. He is a newbie and might not realize it. You'll hate his code deeply a few years down the road." - Sortie
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