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From: Sullivan@cup.portal.com (sullivan - segall)
Newsgroups: comp.sys.amiga
Subject: Re: Whats wrong with self Modifying Code?
Message-ID: <31727@cup.portal.com>
Date: 14 Jul 90 23:28:03 GMT
References: <6180@helios.ee.lbl.gov>
Distribution: na
Organization: The Portal System (TM)
Lines: 33

>In article <14280@venera.isi.edu> rod@venera.isi.edu (Rodney Doyle Van 
>Meter III) writes:
>>  A cache
>> flush might be okay, if it takes less than 50 milliseconds or so.
>> Simply turning the caches off is unlikely to be an acceptable solution.
>
You can turn off the caches independently.  And it may be the only acceptable
solution.  Memory caches aren't likely to be all that effective if you 
are jumping to locations that have to be flushed anyway.  Your other option
is to define the memory that is going to be used for modified code as 
uncacheable.  (Which it is. But which is not supported under AmigaDOS.)

>     So this is simple calculation: the 68030 built-in caches are 256 
>bytes big (as I remember). But if you take the 68040, it's another story 
>as they are 4 Kbytes big (quote me if I'm wrong, I'm not completly sure 
>(-:)

The 68040 snoops the address bus for writes to cached memory, and updates
the cache it is sees any.  (I.e: you shouldn't ever have to flush the 
cache on any processor >= 68040.)  

 
                           -Sullivan Segall
_________________________________________________________________
 
/V\  Sullivan  was the first to learn how to jump  without moving.
 '   Is it not proper that the student should surpass the teacher?
To Quote the immortal Socrates: "I drank what?" -Sullivan
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