jmcgrath at qntm.com
Thu Mar 2 13:54:36 PST 1995
Reply to: RE>SCAM
We crafted the SCAM tolerant requirements carefully so that all devices
shipping for the last 5 years should comply. Basically, people have to
respond to selection quickly, usually automated in hardware. This has
been a feature used in SCSI chips for years, mainly because some early
Macs had a short timeout problem if you did not respond to selection
quickly (similar to the AT write BIOS timeout that forced us all to
implement autowrite). This was fixed through hardware automation
and has been a standard feature ever since.
Date: 3/2/95 12:24 PM
To: Jim McGrath
From: Thomas Tewell
I've been looking over the SPI document and it would appear that it
states that legacy and SCAM devices cannot be mixed on the SCSI bus.
Is this correct? I've been to several 'plug and play' meetings where
much discussion has taken place concerning the proper actions for
mixing the device types on the bus.
Specifically B.3.1 Configuration requirements states:
"a) SCAM intolerant devices (i.e. legacy SCSI devices which are not
SCAM tolerant) are not permitted on the bus."
Does "SCAM tolerant" imply that devices that do not misbehave during
the SCAM protocol are allowed on the bus or that all legacy SCSI
devices are precluded from playing on the bus? The definition states
that "SCAM tolerant" means "An SCSI device which does not implement
the SCAM protocol but which complies with certain requirements
specified by this annex."
How likely is this? Is there anyone testing devices for SCAM
tolerance? It seems to me that there is going to be a GREAT deal of
confusion from the end-users about SCAM. I'm a bit worried that the
computer media pundits will rip SCAM to shreds if we are not very,
very specific about this issue...
Thomas "Rick" Tewell
Sequoia Advanced Technologies, Inc. TEL: (415) 459-7978
55 Shaver Street, Suite 240 FAX: (415) 459-7988
San Rafael, CA 94901 BBS: (415) 459-7977
U.S.A. EMAIL: thomas.tewell at seqadvtech.com
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