[ipxe-devel] 486 with a Realtek 8139

Nikolai Zhubr n-a-zhubr at yandex.ru
Sat May 8 01:03:50 UTC 2021

Hi all,

I've finished with the subject successfully.

What I've done is using prot_to_real implementation in current iPXE, I 
tried to mimic it as much as possible in respective place in Etherboot. 
That is:

- use ljmp instead of lret (after cr0 change);
- assign ss and esp explicitely after that;
- assign all other segment registers explicitely.

Then Etherboot works fine on 486.

So iPXE's implementation is likely correct and supposedly it should work 
too, as soon as all 586 opcodes are eliminated or handled carefully as 
discussed previously. However my brain has pretty much exploded already 
so I'm not going into more testing for now.

Thank you,


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