[OpenBIOS] Beginners How-To for DTS and OpenFirmware?
atar4qemu at gmail.com
Tue Nov 22 15:22:33 CET 2016
On Mon, Nov 21, 2016 at 10:34 PM, Tarl Neustaedter <tarl-b2 at tarl.net> wrote:
> On 2016-Nov-21 15:07 , Michael wrote:
>> Thank you, I found this (and more) last week. The OLPC sites are the
>> best for me:
>> 1: http://wiki.laptop.org/go/Open_Firmware
>> 2: http://wiki.laptop.org/go/Forth_Lessons
>> 3: http://wiki.laptop.org/go/Cross_Compiling_Open_Firmware
> Some history behind that...
> Back in the dim, dark past (1980's), Mitch Bradley worked for Sun
> Microsystems on system startup. At some point, he left to create a
> startup (firmworks.com), and produced a forth kernel used for booting
> SPARCs, which sun adopted for the sun4c models and later. They worked
> together at producing an IEEE standard, IEEE 1275-1994.
> For a long time, Sun and Firmworks exchanged source code (I think
> actually mostly Firmworks to Sun, but formally listed as exchange).
> During that period, several other companies produced systems based on an
> OpenFirmware initialization (Motorola, Apple & IBM's PPC implementations
> are the ones which come to mind). As I understand it, these were
> entirely separate implementations based on the IEEE 1275 document.
> Fujitsu based their systems on a SPARC core, and I believe based their
> code on Sun's implementation.
> Decades went by, and industry interest in OpenFirmware waned (mostly
> because EFI came on the scene, and for all its faults, it did adopt most
> of OpenFirmware's important concepts [...]
That's a very interesting point. Does EFI actually have any advantages
over IEEE 1275?
For instance, Apple moved to EFI, but was their real motivation?
Did they just wanted to ditch Forth?
> Mitch got a contract to help the One-Laptop project with their BIOS work
> and eventually persuaded them to ditch the traditional PC bios and
> instead use a forth-based initialization, based on Firmwork's
> OpenFirmware implementation. There were a number of factors involved,
> primarily being that they were tremendously prom-limited, and a forth
> implementation can pack in more functionality per byte than ordinary
> executable code can.
Also the first versions of OLPC were not based on x86 CPUs, so there
was no requirements on the PC BIOS compatibility initially.
> Since Mitch is the leading prophet of the OpenFirmware cult, he's made a
> point of carefully documenting everything involving OpenFirmware on
> One-Laptop. So anything you find under laptop.org is going to be the
> most recent edition by the person who knows the most about the standard
> and implementations.
SPARC and PPC PReP under qemu blog: http://tyom.blogspot.com/search/label/qemu
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