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Re: Should we have SCSI? And other ramblings...

To: riscy@pyramid.com
Subject: Re: Should we have SCSI? And other ramblings...
From: jcn@jcnpc.cmhnet.org (James C. Nugen)
Date: Sun, 4 Jul 93 10:15:27 EDT
In-reply-to: <9307040427.AA17852@sword.eng.pyramid.com>; from "Neil Russell" at Jul 3, 93 9:27 pm
Reply-to: riscy@pyramid.com
Sender: riscy-request@pyramid.com
> If we intend to provide SCSI on ISA rather than the mother board,
> we need to provide bus mastering capability to the ISA bus.

Why? We don't need bus mastering because there is no 16Mb limitation. And
having the SCSI controller on the motherboard won't buy you much of a speed
improvement. The main reason that PC's have these problems is due to the
use of 8237-like DMA controllers. We won't be using them. If the ISA bus
interface connects the DMA request from the bus to the 3730, then it will be
effectively the same as having the SCSI controller on the motherboard. This
would allow people to add SCSI if they want it by adding one of the cheaper
non-bus mastering controllers like the Future Domain's,etc.

Same thing as above goes for the ethernet port.

I believe that the motherboard should have nothing on it except the CPU,
3730, keyboard controller, RTC & NVRAM, glue, and memory. Everything else
should be on the ISA bus, with the exception of video.

If the user wants to get going cheap, they should be able to put a cheap VGA
card in the ISA bus. But if they want to have faster video, we should have a
special video slot. We could use a VESA slot if it is not to hard to implement,
or have our own custom video slot. This way we can have different video card
designs. If some one wants to make a 34010 card or a dumb frame buffer card,
they can just design it to plug into the video slot. Others will have the
choice of using which ever video card they want and can afford.

James C. Nugen


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