riscy
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Re: More ramblings...

To: SMACKINLA@cc.curtin.edu.au (Pat Mackinlay)
Subject: Re: More ramblings...
From: Stephen Siu-ming Wong <a080700@hp750a.csc.cuhk.hk>
Date: Sun, 27 Jun 93 22:07:00 HKT
Cc: riscy@pyramid.com
In-reply-to: <01GZVM88DN3EFUMJ82@cc.curtin.edu.au>; from "Pat Mackinlay" at Jun 27, 93 4:32 pm
Mailer: Elm [revision: 70.30]
Hi Risciers,

>* Dual or quad UART: gives us important motherboard-based serial ports for 
>mouse/terminal/modem.

I heard it once, and would like to bring it out again, will the Zilog SSC
be a better choice?  As I remember, it is a dual USART chip, and capable
to do sync and async.

>* Video controller: I'm still for a TMS34010-based solution. Here, the 
>problem is mainly software. I think using this chip would help to cut total 
>system costs quite remarkably. Steve's probably going to flame me about the 
>NSC chip, but I think I prefer this one.

Good enough, but still better to use VRAM as frame buffer for TMS and a
24-bit RAMDAC.

>* Ethernet controller: Providing it's cheap enough, it looks like the NSC 
>8390 and it's interface chip might be the right way to go here. If the 
>devices are expensive, I'm in favour of leaving this section of the board 
>unpopulated.

If we are not going to implement ISA bus, 8390 may NOT be the best choice,
some new LANCE chip should have a much better performance than 8390.
Moreover, 8390 is a rather dumb device, why not using a better chip?

One point I would like to raise, since we aim at PC board form factor,
does anyone think about how to put the ethernet connector on the mother
board and still accessible from a normal PC case?  There's a hole near
the rear right hand side for keyboard connector, but no other convenient
opening, how to deal with it, drill a hole on the case?

>* SCSI controller: I think we've pretty much settled on the 53c94? Again, I 
>don't have pricing info, but I think it's reasonable. This chip is pretty 
>vital to the whole system, and I personally think the 53c94 is the best 
>chip for the system.

Is it SCSI-2?

>* Boot EPROM: This is pretty straightforward. How much are we shooting for? 
>I'd suggest 64k or 128k - I don't think we can really use much more than 
>that. I'd like to have a complete system configuration/testing program in 
>this along with the code necessary to read a boot image from SCSI, Ethernet 
>and serial interfaces. I am willing to spend quite a lot of time on this to 
>make it right <grin>.

Do you mean boot from SCSI device (disk AND tape), Ethernet (bootp and tftp)
and some proprietry serial booting interface?

>* I/O bus: I have personally given up on the idea of an ISA bus. No one 
>seems to have come up with an easy and cheap solution to implement one. I 
>do like Steve's simple/proprietry 8 bit I/O bus, but I'd prefer not to have 
>to have the 3041. I think this interface could be stuck onto the 3730 
>relatively easily, and think it would serve all our needs as far as simple 
>expansion goes. I really can't think of an ISA-based I/O device that anyone 
>would want to add to this system that couldn't also be done with the 
>proprietry interface. Again, I'd vote for leaving the I/O connectors 
>"unpopulated" if they are a significant cost.

If no ISA bus, then we have to adjust our minimal device list on board,
such as floppy disk controller (much much cheaper than SCSI floppy),
bi-directional parallel port (almost a must), sound support (like 16-bit
stereo AD/DA, FM, PCM).

--
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