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gPXE currently takes advantage of the feature of PCI3.0 that allows option ROMs to relocate the bulk of their code to high memory and so take up only a small amount of space in the option ROM area. Currently, the relocation can only take place if the BIOS's implementation of PMM can be made to return blocks aligned to an even megabyte, because of the A20 gate. AMI BIOSes, in particular, will not return allocations that gPXE can use. Ameliorate the situation somewhat by adding a prefix, .hrom, that works identically to .rom except in the case that PMM allocation fails. Where .rom would give up and place itself entirely in option ROM space, .hrom moves to a block (assumed free) at HIGHMEM_LOADPOINT = 4MB. This allows for the use of larger gPXE ROMs than would otherwise be possible. Because there is no way to check that the area at HIGHMEM_LOADPOINT is really free, other devices using that memory during the boot process will cause failure for gPXE, the other device, or both. In practice such conflicts will likely not occur, but this prefix should still be considered EXPERIMENTAL. Signed-off-by: Marty Connor <mdc@etherboot.org>
gPXE README File gPXE is an implementation of the PXE specification for network booting, with extensions to allow additional features such as booting via HTTP, iSCSI, and AoE. In generally, gPXE is compatible with the industry-standard PXE specification, and also supports Etherboot .nbi file loading and some additional protocols and features. For more detailed information about gPXE, please visit our project website at: http://etherboot.org/ BUILDING gPXE IMAGE FROM SOURCE If you don't want to install development tools, and have access to the Web, you can get gPXE and Etherboot ROM images made on demand from http://rom-o-matic.net/ If you would like to compile gPXE images from source, here are some tips. We normally compile gPXE images on x86, 32-bit Linux machines. It is possible to also use x86-64 machines. We use gcc compiler options to create 32-bit output. It is important to have the necessary software packages installed. A gcc-based toolchain is required. The following packages (at least) are required: - a gcc tool chain (gcc 3.x or gcc 4.x) - binutils - perl - syslinux - mtools To test your environment, cd to the "src" directory and type: make You should see a lot of output, and when it stops, the "bin" directory should be populated with gPXE images and object files. To learn more about what to build and how to use gPXE, please visit our project website at http://etherboot.org/ , particularly the "howto" section. CONTACTING US Pointers to our project mailing lists are on http://etherboot.org/ Real-time help is often available on IRC on the #etherboot channel of irc.freenode.net.