I want to mess with the MBR (master boot record) partition table on my SD card, potentially corrupting the MBR. I am fully aware that I may end up corrupting partition content in the process if I let RPi try and boot from a random location of the card. Anyway, on to the concrete problem I have:
The problem is that I don't know of any way to directly read or write to the card in Windows 8, which my desktop computer currently run. Raspbian has the nice
dd command and direct memory access via
/dev/mmcblk0 so I can read and write specific bytes directly to the memory card. But if I mess up the boot loader so the GPU can't run the bootcode and load my kernel, then I have no way to restore the changes to the MBR partition table.
Since I only have Windows 8 available at the moment, I'd like to get access to the card to peek and poke data from Windows 8. If the operating system have no tools to directly access my SD card through my SD card reader, can you recommend any software that is capable of writing specific bytes (while keeping the rest of the memory card unchanged)? At the very least I want the replace the first 512 bytes.
I know I can make a full image clone of the drive, but I don't want to write the entire image when I don't have to.