Subject: Re: About the QBus EIDE interface...
To: None <port-vax@netbsd.org>
From: John Maier <jmaier@midamerica.net>
List: port-vax
Date: 01/24/2002 12:31:16
> ok, ill help hack on the MSCP stuff. I dont have time for a full fledged
> project, though, but i can help.

I'm sure, if I can get rolling, I will have questions.

> from what i see, well need some Qbus glue, a cpu with MSCP code loaded in
> from rom, a meg of memory or so, an IDE controller, and appropriate logic
> so that the cpu can talk to the qbus and ide driving hardware. i dont know
> much about qbus internals, and the IDE chip will be off the shelf, so i guess
> ill be concerned with what kind of interface ill see from the qbus side?
> Also, has there been any more decision anywhere on what kind of cpu?
> as long as there's a sane C compiler for it, i'm cool with it.. though i'd
> on principle try to avoid an intel design (a strongarm, while made by intel,
> is a DEC design, so thats cool by the Chip Ideology :-)

I would like to avoid Intel stuff too, but cost is cost, time is time and support is
support.
As for C compiler, I had an ASM solution in mind, partially for performance, and the C
kits for ROM/Embedded stuff, tend to be pricey.  I don't know much about the Strongarm
chip.  The other delima is packaging.  So many CPU are comming in just QFP and I just
don't have surface mount equipment!  PLCC or PGA are much nicer to work from, from a
hobbiest position, so this is a factor too.  This doesn't mean it can't get to a surface
mount for a final step.

> and though i dig Z80 stuff i dont know anything about the later zilog
> chips. as for memory, unless the chip we use has a dram controller on it
> or comes with one, i dont even think we should bother with it. half a meg or
> a meg of cheap sram shouldnt cost much, and it keeps our component count
> down and makes the board simpler (i think the pcb might be the most
> expensive thing in it) (i assume were doing a half-sized qbus card, right?
> no need for a quad-height.
>
> so, comments about the cpu?


Per DigiKey (US)
386DX (33Mhz)(PGA) = $44
386SX (33Mhz)(QFP) = $15
Z380 (20Mhz)(QFP)  = $20
Strong Arm SA-110 (166Mhz)(QFP) = $34
MC680x0 020-060 = all over $130

From a cost/performance the 386SX seems the best..but it QFP and I can't do surface mount.

BTW, the Zx80 had built-in DRAM refresh, which make working with them nice.

All that said, if any one knows someone/someplace that will place surface mount QFP on top
of a PGA or PLCC, let me know.

jam