Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!sun-barr!ames!ncar!noao!asuvax!mcdphx!teroach.UUCP!dbk
From: dbk@teroach.UUCP (Dave Kinzer)
Newsgroups: comp.sys.amiga
Subject: Re: GVP 68030 reviewed in Sentry
Summary: More Cache warnings
Keywords: Cache
Message-ID: <11044@mcdphx.phx.mcd.mot.com>
Date: 9 Jun 89 14:38:17 GMT
References: <2461@van-bc.UUCP>
Sender: listen@mcdphx.phx.mcd.mot.com
Reply-To: dbk@teroach.UUCP (Dave Kinzer)
Followup-To: comp.sys.amiga
Distribution: na
Organization: Motorola Microcomputer Division, Tempe, Az.
Lines: 39

In article <2461@van-bc.UUCP> lphillips@lpami.wimsey.bc.ca (Larry Phillips) writes:
>There are only two choices here, one being to disable the cache (I don't know
>if you can disable data cache separately from instruction cache), and the

It is and you can.

>other is to use a 'Mask = ' entry in the mountlist to limit DMA to the 16 bit
>memory. GVP claims that it is better to do the latter, since the 68030 is fast
>enough to make the programmed IO transfer speeds go very quickly.
 
>-larry
 
>+----------------------------------------------------------------------+ 
>|   //   Larry Phillips                                                |
>| \X/    lphillips@lpami.wimsey.bc.ca or uunet!van-bc!lpami!lphillips  |
>|        COMPUSERVE: 76703,4322                                        |
>+----------------------------------------------------------------------+

   Unfortunately, I have been known to load a program or two in my usage of
my Amiga.  If the program is transfered using DMA, there is a possibility
of stale data in the instruction cache.  The 68030 cache is not exactly
a Most Recently Used cache, some stale data can exist even after thousands
of instructions have been executed (though not likely [read infrequent guru]).

   I seem to recall a flush cache system call, but I could not find it in
about 2 minutes of looking.  If it does not exist, it needs to (can you say
1.4 wish?  I knew you could.)  It perhaps should be implemented as something
external to the system (Romtags?), so as new processors become available
it can be easily changed (Also changable for aftermarket cache boards should
they become available.)

   Any task that is in control of DMA (say, the trackdisk device) would call
this routine after the DMA is finished.  The routine would flush the cache
if it exists.

   
|    // GOATS - Gladly Offering All Their Support  Dave Kinzer (602)897-3085|
|   //  >> In Hell you need 4Mb to Multitask!  <<  uunet!mcdphx!teroach!dbk |
| \X/   #define policy_maker(name) (name->salary > 3 * dave.salary)         |