PCMCIA card as bootloader?
category: code [glöplog]
Wikipedia sez:
What I would like to have is a PCMCIA card with just a small flash chip mapped to the ISA memory space for experimentation. Are there such cards? (The only thing I could find with some quick research was ATA cards, which is basically IDE and not directly mapped memory.) Has anyone here done anything like this? Do all BIOSes do this search, etc?
Quote:
This could be used for all sorts of fun and useful stuff. For example, surprise, bootloaders. For example to add boot options to old computers,In order to discover memory-mapped ISA option ROMs during the boot process, PC BIOS implementations scan real memory from 0xC0000 to 0xF0000 on 2 KiB boundaries, looking for a ROM signature: 0xAA55 (0x55 followed by 0xAA, since the x86 architecture is little-endian). In a valid expansion ROM, this signature is immediately followed by a single byte indicating the number of 512-byte blocks it occupies in real memory. The next byte contains an offset describing the option ROM's entry point, to which the BIOS immediately transfers control. At this point, the expansion ROM code takes over, using BIOS services to register interrupt vectors for use by post-boot applications, provide a user configuration interface, or display diagnostic information.
What I would like to have is a PCMCIA card with just a small flash chip mapped to the ISA memory space for experimentation. Are there such cards? (The only thing I could find with some quick research was ATA cards, which is basically IDE and not directly mapped memory.) Has anyone here done anything like this? Do all BIOSes do this search, etc?
