On Tue, Jan 20, 2009 at 10:54:02PM -0800, David Ross wrote:
Random question...
In the Atari OS (TOS) for the TT030 there's a way to view/set the state
of the 68030 cache. I've been curious to find out if the CPU cache is
enabled when I'm in NetBSD. Anyone know, or know a quick way to to get
the info at runtime w/o learning 68030 assembler? =)
You can't - but it is. Details: it is selectively enabled via the
MMU for main memory during early boot time. Lines about 1013 and
following in sys/arch/atari/atari/locore.s:
... movl #CACHE_ON,%d0 ;valid for '020/'030
cmpl #MMU_68040,_C_LABEL(mmutype)
jne Lcacheon
[68040 and 68060 code here]
Lcacheon:
movc %d0,%cacr
(The cache control register is priviledged-code-only, you can't even
read it from user code, that's why you can't easily check it.)
The MMU tables are set in a way that memory regions are using the
cache. Device registers, of course, are mapped uncached.
-is