Subject: Re: pthreads
To: Ty Sarna <tsarna@endicor.com>
From: Chris G Demetriou <Chris_G_Demetriou@lagavulin.pdl.cs.cmu.edu>
List: amiga
Date: 06/13/1995 18:00:32
> Yes, it is a hardware issue. TAS screws up DMA in the chip memory space.
> It is also not safe to use it outside of chip sapce as well, according
> to Dave Haynie, because a lot of memory (and CPU board) designs ignore
> the issues. ("Hey, the manuals say TAS isn't allowed, so I guess we can
> just ignore it". An understandble position). I bet GVP boards rank top
> among them :-)

... so now i wonder how page table accesses/updates work properly...

> Oh, on the '060 (and '040??) TAS/CAS/CAS2 are not implemented anyway,
> they have to be emulated, so one might as well use the syscall in those
> cases, since all that overhead is there for TAS as wel in that case.

Actually, it's reasonably likely that those instructions would be
emulated via a "fast path," probably even with motorola-supplied
code, so a syscall's overhead would be... undesirable.


chris