Re: [Qemu-devel] Support NEC PC-98x1 on QEMU

[武田 俊也]

Dear Stuart,

>There's no need to add this as a whole new architecture, although
>perhaps the use of TARGET_PC98 was only meant to be temporary...

The problem is that now TARGET_I386 is used for both 2 meanings,
cpu is i386 and the arch is PC/AT.

I used TARGET_PC98 for the meaning cpu is i386 and the arch is PC-98x1,
so I needed to change every defined(TARGET_I386) used for the meaning
the cpu is i386, to defined(TARGET_I386)||defined(TARGET_PC98).
I agree this is not good.

I suggest adding the definition TARGET_PCAT to divide theses meanings
so we can easily add none PC/AT machine with i386 cpu like PC-98x1.

For PC/AT:
        #define TARGET_I386
        #define TARGET_PCAT
For PC/AT x64:
        #define TARGET_I386
        #define TARGET_X86_64
        #define TARGET_PCAT
For PC-98x1:
        #define TARGET_I386
        #define TARGET_PC98

I will post the patch before repost PC-98x1 patch.


About A20 line gate:

In PC/AT arch, only A20 line is masked and when cpu is reseted it is not masked.
You know, In PC-98x1 arch, A20 and upper lines are masked and when cpu is 
reseted 
they are masked.

Now A20 gate is hard-corded in i386 core, but it is only PC/AT specifications
probably by external circuts, not cpu internal.
It may be possibly better to move a20 gate codes to pc.c and pc98.c,
but I think it is allowable to keep them in cpu core with #ifdef for each arch.

I want your comments.

Thanks,
TAKEDA, toshiya