Subject: NCR 810 vs. BT946C -- Efficiency?
To: None <port-i386@sun-lamp.cs.berkeley.edu>
From: Thor Lancelot Simon <tls@panix.com>
List: port-i386
Date: 11/08/1994 20:04:21
I'm looking at buying another PCI-bus machine.  The other ones I've got have
BT946C controllers, which I'm pretty happy with, but which cost a bit more
money than I'm comfortable paying.  The vendor of the machine I'm looking to
buy says that for $100 he can toss in an ASUS SC-300 controller, which is an
810-based fast/wide SCSI controller.

Having just taken a preliminary wander through pci/ncr.c, I notice a few
things: 

A) for some reason, the driver seems to turn synchronous transfers off.

B) for some reason, the driver seems to turn wide transfers off.

C) at first glance, it looks like the 810 doesn't do busmastering DMA.

These "features" seem to be shared with the driver for the Adaptec chip on
those soundblaster-scsi cards, which I remember ultimately being only a
little, little bit faster than an IDE disk.  So I'm wondering -- am I wrong
about point C, or if I'm right, doesn't this imply that the 946 is likely to
be by far the faster of the two cards?  Also, why are synchronous and wide
transfers turned off by default, and will Bad Things happen if I turn them on?

Lastly, can anyone else give me some real numbers on an 810-based SCSI
lash-up, or should I just go buy the ASUS card and find out for myself?  At
$100, the thing is very, very appealing -- but if it doesn't perform at least
as well as a BusLogics controller, I'll be pretty disappointed.

Thor