Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!cs.utexas.edu!uunet!iconsys!caeco!i-core!geo-works!bryan
From: bryan@geo-works.UUCP (Bryan Ford)
Newsgroups: comp.sys.amiga
Subject: Re: Software-only network protocol standards
Message-ID: <1993.AA1993@geo-works>
Date: 28 Jul 89 23:24:41 GMT
References: <1789.AA1789@geo-works> <117428@sun.Eng.Sun.COM>
Followup-To: comp.sys.amiga
Lines: 42

In article <117428@sun.Eng.Sun.COM>, cmcmanis%pepper@Sun.COM (Chuck McManis) writes:
>> I'm
>>assuming that most Unix boxes run at much higher speeds, and since they
>>inherently *require* at least a 68020 (if memory protection is supported),
>>many of the instructions will also execute in less clock cycles (the 68020
>>often uses less clock cycles per instruction).
>
>This is a bogus assumption. The Sun-1 was a 68000 and the Sun-2 was a 68010.
>The latter was running at 12Mhz I believe. But it did have memory management.

I stand corrected.  Please clarify 'memory management':  You don't include
memory protection, do you?  How could a pre-68020 provide memory protection
unless it has some special protection hardware?  (Did it?)

>This says that for any stream of bytes at 200,000 baud, we should be able
>stuff them from the serial port into a buffer. With some time to spare
>something like (my assembler for the 68K sucks, please forgive):
>
>...
>
>$10	tst.b	SERFLAGS,#DATA_AVAILABLE  ; guarunteed to be ~400 clocks
>	bz.s	$10			  ; so busy waiting is ok.

So, you're saying that interrupts are too slow to do anything but busy-wait
after the beginning of the packet has been detected?  Too bad.  I was
hoping that some needy task could get some precious CPU between the bytes,
but it looks like this was a hopeless hope.  :-)

> [lots of other good stuff]

Thanks very much for the tips and the routine!  They are going to help a
lot!

				Bryan

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