Re: [Nubus-pmac-users] Re: Re: Powerbook 1400 Media-Bay

[Tobias N. <tob...@t-...>]

Am 12.03.2006 um 00:21 schrieb Daniel Gimpelevich:

> On Sat, 11 Mar 2006 20:38:18 +0100, Tobias Netzel wrote:
>
>> I also modified your C translation to use the "in_8" and "out_8"
>> functions that should do everything necessary - "include/asm-ppc/io.h"
>> says that they include "barrier" what I think is the same thing as
>> eieio does.
>> But there is no difference in behavior to the versions without
>> "barrier" or the ones created by PortAsm.
>
> Part of the difficulty may be that the m68k architecture has no native
> support for PIO, only MMIO. Trying to figure out where the code should  
> use
> PIO and where it should use MMIO is not something for which I was  
> prepared.
>
The NuBus PMacs are not much more than 68k Macs with a PowerPC CPU.
Everything is mapped into memory and there are no I/O ports.
When one compares the developer notes of the PowerBook 190 (68k) and  
the PowerBook 5300 (PPC) one will not find many differences.
The difference ia an adapted memory controller in that case -  
everything else is the same.
So there shouldn't be a problem with PIO.

But the swim driver is far from being complete (no write support) and  
in my opinion it isn't worth the effort putting much time into getting  
it to work

>> Are you interested in the object files that gcc creates or the code
>> that PortAsm produced?
>
> I would be interested in obvious differences between them, but my
> knowledge of PowerPC assembly never progressed to the same level as for
> m68k, so details may exceed my current level of understanding.
>
>
PortAsm replaced every 68k instruction by one or more PPC instructions  
step by step. It mapped the registers into PPC registers and also  
"emulated" the 68k stack in a PPC register.
It added some "glue" code to interface with the C calls.
It took some hours to understand the manual and get the file translated  
into a usable form.
>
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