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usb flash drive as floppy disk or cd drive


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#1 florin91

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Posted 4 weeks ago

Hello,

Can I make a usb flash be detected and act like a floppy in windows?

Possibly without grub4dos and more like dd, fdisk or rmprepusb tools.

I am certain this is possible in a hardware way by manipulating controller chip and rewrite its memory, and I wanted to know if it might be possible by software.

Obviously, simply dd'ing the floppy image to usb doesn't work.

You might want to say to use a floppy disk. I know how a floppy disk looks, but given the notebook manufacturers consider it out of spec there might be some usb way, since we have usb ports.

You might ask why I need this? For flashing bios recovery under dos. There is a recovery bios key combination
( fn +b + power)
which when pressed attempts to read for a floppy or usb containing the bios to write and other dos tools.

One problem that I might be encountering is using 32 gb usb formated with a partition with 1 gb for using fat filesystem.

And I need to disassembly more the recovery part from the bios in order to find the filename...

Thanks!

#2 steve6375

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Posted 4 weeks ago

Most BIOSes will access a FAT32 USB drive just fine.

Are you encountering a problem?



#3 florin91

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Posted 4 weeks ago

Yes. While pressing the combination for bios crisis recovery, it reboots, this means something with the flash is not right. Will try further. From this the ideea if I can make the flash detected as a floppy drive because I have a recovery floppy binary image. Or as a cd because when disassembling bios code I saw a bunch of ELTORITO specifications.

So, can I plug a usb and the bios detect it as floppy?

Will recheck the stick creation.

Edit: Most bioses will access the usb just fine when running at full capacity and integrity. But IF this is a part from a bios ( from a bad bios flash), especcially the BIOS block which deals with a restrained system and offers small recovery procedure?

Edit2: The eltorito spec support floppy booting with cds...

#4 tinybit

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Posted 4 weeks ago

Basically you could not expect BIOS works for ever. The manufacturers are dropping BIOS support, using EFI instead.



#5 steve6375

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Posted 4 weeks ago

You can try using RMPrepUSB to prepare the USB drive.

Use 

Size 300

MS-DOS

FAT16

Boot as FDD

 

and place files on USB drive afterwards.

 

If that fails, try FAT32.

Also, use the smallest USB flash drive you can find !



#6 florin91

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Posted 4 weeks ago

You can try using RMPrepUSB to prepare the USB drive.
Use 
Size 300
MS-DOS
FAT16
Boot as FDD
 
and place files on USB drive afterwards.
 
If that fails, try FAT32.
Also, use the smallest USB flash drive you can find !


Ha ha smallest usb yes, I know!

It is interesting how the smallest usb you can buy these days is 4 GB when I wanted 2 GB or less ... So I will try that! One can even host a contest - the smallest usb you can buy ...

Now I tried with 4gb and the WinCrisis phoenix tool. Didn't worked.
To try next:
- Steve method: How can I flash custom boot sector.bin in RMPrepUSB? Wanted to try 300 size, FDD boot and a custom boot sector other than the ones listed? Maybe with DD too.
- create a virtual IMG file, mount as floppy, use WinCrisis app and then DD the image to usb
- using the previous image create an EL TORITO boot as FDD CD image to burn and try that instead ...
- disassembly more bios to see why it's not recognised ...
- buy a cheap eeprom programmer and use that since the BIOS chip is removable dip package yes.

Any thoughts?

#7 Wonko the Sane

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Posted 4 weeks ago

In some cases, historically a "double way" approach, i.e. something that is at the same time a super-floppy and a partitioned hd-like device worked around some BIOS issues (please read as makebootFAT), but if the issue is with the BIOS "emergency block" and somehow you need it to become "drive A:" it is entirely possible that an actual floppy (and nothing else, exception made for some - now not findable anymore - USB sticks, I seem to remember by Netac, Steve6375 used them, that had a physical switch to emulate a floppy) would do.
But, usually, a USB floppy drive works, of course it depends on specific motherboards/BIOSes.

A floppy emulation El Torito also should get drive A:.

The "easiest" (not necessarily the best) way to make such a CD from a floppy image is referenced here:
http://reboot.pro/to...brided/?p=86679
http://www.menuetos.net/cdboot.htm

:duff:
Wonko

#8 florin91

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Posted 4 weeks ago

Thank you, will try!

I was thinking it would be easier if I use mkisofs from cdrtools.

Something like this:
mkisofs -r -b boot/boot.img -c boot/boot.catalog -o bootcd.iso .
Thanks!

Edit: I am the only one this website seems to sign out? Whatever ...

https://support.micr...bootable-cd-rom

#9 cdob

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Posted 4 weeks ago

Now I tried with 4gb and the WinCrisis phoenix tool. Didn't worked.

A 2GB or less USB drive is recommended.
http://forum.noteboo...s-flash.529859/

Do you have a old MMC or SD card?
I'm using a 16 MB MMC card and a USB card reader for booting DOS.

#10 florin91

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Posted 4 weeks ago

Unfortunately not, 4 GB usb and 4 GB micro SD card as well.

I don't understand why won't support bigger ones, if the first partition is small.

And regardless of size, when executing the correct jmp of instructions, it should try continuously reading the flash.




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