*BSD News Article 25553


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Newsgroups: comp.os.386bsd.development
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From: jmonroy@netcom.com (Jesus Monroy Jr)
Subject: Re: [FreeBSD 1.0R] DMA Problems?
Message-ID: <jmonroyCJ3u56.1us@netcom.com>
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References: <jmonroyCIHJA2.oy@netcom.com> <2fl24q$jn2@u.cc.utah.edu> <JTW.94Jan3234318@pmws.lcs.mit.edu>
Date: Tue, 4 Jan 1994 12:17:30 GMT
Lines: 68

John Wroclawski (jtw@lcs.mit.edu) wrote:

: In article <jmonroyCIvwpv.8F3@netcom.com> jmonroy@netcom.com (Jesus Monroy Jr) writes:

:    To clarify the issue: DMA DRAM refresh skipping would be a 
:    bad term to use.   What happens is the timer for channel 0,
:    the DRAM refresh timer, is reprogrammed so that there are 
:    less refreshes per second (ie. 2000 new vs. 3000 old refreshes
:    per second)...

:    It is possible, via software, to reprogram the refresh cycle.
:    My example program does this.  The results are had when the
:    system crashes.  That is, to make this a software *probe*
:    the program would (if it existed for *BSD) slowly turn down
:    the timer till the system crashed.  At this point, some
:    test could readily determine the *consistency* of ths system.

: This won't work very well.

: It is impossible to -probe- for a minimum DRAM refresh rate because
: the answer is not binary. If you avoid refresh for long enough, yes,
: the data will flat-out be lost. But long before that the DRAM will
: simply become much more sensitive to power supply noise, cosmic rays,
: lightning, and all of the other things that occasionally cause DRAMS
: to lose data.  Unless you can duplicate all of these external events
: during your probe operation, you cannot even begin to predict when the
: RAM will fail.
:
	I'm sorry for this reply... but

	Sagitarius (sp?) won't align with the moon for at least
	four days.... Can I give you an answer then?

	What is this "cosmic ray" stuff?
	Somebody please tell me if I should take this seriously?


: For what it's worth most DRAMS operating at room temperature will hold
: bits fairly well for at least ten times longer than the specified
: refresh interval. This value falls rapidly at higher temperatures. At
: the specified maximum operating temperature, the longest time you can
: wait safely is fairly close to the listed refresh interval.
:

	Look, here are the facts....

	There are tweleve women of asian decent with a 
	birth defect rate of about 50% that produce these
	chips.   Companies with mucho bucks pay them
	next to nothing to work like slaves.....

	Two days a week they get drunk and 7 of the 12 
	women make the chips you and I will be testing 
	next week... 

	Please quote the literature... or at least the the K&R book.

	Tell me I'm an idiot or something... but please...
	enough speculation....

: John Wroclawski
: jtw@lcs.mit.edu

-- 
Jesus Monroy Jr                                          jmonroy@netcom.com
Zebra Research
/386BSD/device-drivers /fd /qic /clock /documentation
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