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From: teener@apple.com (Michael Teener)
Newsgroups: comp.sys.mac.hardware,comp.sys.mac.programmer
Subject: Re: NuBus traffic
Message-ID: <14065@goofy.Apple.COM>
Date: 14 Jun 91 02:27:46 GMT
Sender: usenet@Apple.COM
Organization: Apple Computer, Inc.
Lines: 28

In article <1991Jun13.183543.12392@umbc3.umbc.edu> brian@umbc4.umbc.edu 
(Brian Cuthie) writes:
> Because
> the NuBus is such a pig (at best, on a good day, ~30 Mbytes/sec, block mode)
> there is a real bottleneck between the processor and the video ram.  Worse,
> the NuBus is EXPENSIVE to design interfaces for.  Even the chipset that
> TI has is $50 in quantity.

With all due respect, NuBus is not a pig. 32 Mbytes/sec is roughly four 
times faster than its earlier IBM peers ... and is still faster than all 
MicroChannel versions until very, very lately. *And* there is a new and 
completely compatible version of NuBus recently finished by the IEEE 1196 
working group that supports transfers up to 78 Mbyte/sec (along with cache 
coherency and a few other interesting upgrades).

And regarding the cost: the TI transceivers are OK for prototyping, but 
the controller is a joke.  Both parts are *too expensive*. If you look at 
the NuBus cards done by Apple, Supermac, Radius, etc ... you will find 
that all the interfaces are done using off-the-shelf transceivers and 
semicustom controllers (slave boards without burst mode can get by with a 
single PAL).  You pay for what you get ... a non-burst slave interface 
will cost less than $10, a bursting master can cost $35 and require a 
semicustom controller.

======== routine disclaimer ================= I yam what I yam ========
Michael Teener, Staff Busybody, International House of Technology
                     (*and* IEEE 1196 Chair)
==== Not flying nearly enough these days, Cheetah N9900U is lonely ====