riscy
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Long ramblings about project design

To: riscy@pyramid.com (Mips 3000)
Subject: Long ramblings about project design
From: Bill Broadley <broadley@neurocog.lrdc.pitt.edu>
Date: Fri, 25 Jun 1993 04:47:56 -0500 (EDT)
Just more random thoughts on the project from my hardware naive view:

The goal of the project seems to be to have fun building/designing a
new motherboard that is fast, clean, low parts count, with a nice cpu on it.

Kinda of a poor man's workstation that doesn't benefit microsoft or intel.

Since most of us can't spend $700 or so on a whim we would consider it
quite an investment. (I'd sell my maxed out 386-40+387 for one)

The minimal cost solution would a cpu+ram on a ISA slow, but this seems of 
little utility and would be quite ISA limited.  I'd guess the cost would 
be around $150-$200 above the cost of the cpu?

Despite ISA's bad reputation it handles up to 4-5 MB a second which, despite 
the advertising, is enough for most users bus needs with the possible exception
of high resolution video.  Not many people need more then 4 MB/sec for disk 
bandwidth etc.

So if you add video support on board you have greatly reduced your
load for the ISA bus at the cost of 1 MB vram + support chips ($60-$75)?

I believe that VESA support is almost free (simple bus) is this true?
Are non-surface mounted chips available?  A fairly high end VESA local
bus S3 805 can be had for less then $200 (+ cost of supporting vesa).
I see VESA as the only possibility for future expansion, because EISA
is to expensive ??  Vesa nicely  maxes out at 40 Mhz to ;-)

I'd say if we can get half the performance for less then half the price
and forget VESA bus, otherwise it's an option (somebody posted a do it 
all chip that supported vesa, haven't heard of availability yet).

Apparently the TI34020 is a fairly powerful chip (used in xterminals from 
tektronics, and high end (> $1k) video cards.  I know of no free drivers and 
I suspect that they would be quite involved to write them (I believe I've seen 
entire X11 servers running on them, which would be WAY cool.)  I am suprised 
they are cheap and would volunter to attempt an X11 driver for that chip.  
But writing a X11 server for a TMS34020 is beyond me, as oppsed to a driver 
which I think I could get to work.  Am I thinking of the correct chip here?

As an interesting side note Tektronics gave up on there xterminals with
68030's at 20 Mhz and TI 34020 chips at 40 Mhz because they were to slow
they switched to mips 3000's.  Wonder if tektronics would release there
tiga drivers ;-)

Apparently a SCSI buss is pretty cheap (Did I hear $5.00?) I'd suggest
SCSI-II 5 MB/sec as a minimum (scsi-II is supposed to be "defined" then
scsi-I so hopefully less compatibility problems).  No need for more
speed really (most drives can handle max 1.0-1.5 MB/sec real world).
It's a BIG win if it's as cheap as I thought I heard.

By this time it's probably better to go with a motherboard as opposed to
a ISA card, we have already gotten rid of the 2 biggest bus users.  

How many people who want a mips have ethernet?  I don't. Why not 
standardize on say a WD8013? It has a 32 k cache or so and ethernet is a 
MAX 10 megabit, or 1.25 MB which the ISA should handle fine (especially since 
we have fast int cpu).  Remeber disk, and video are already on a different bus.
(Either VESA or native) Is it cheaper to do it on board? 

If you don't put ethernet on ISA why bother with ISA? You really want a sound 
blaster (remeber ya got to write the drivers) almost any magic ISA video card 
will be slower then VESA/NATIVE cards.  Serial is easy, parallel isn't that 
used (by me anyways 8-) ), and floppies can run on SCSI (granted not cheaply).

I know it hurts to have a board without slots, but the ISA is limiting enough 
so anything new and hot won't be happy in a ISA slot anyways. thats why we 
are not producing a ISA card right?

So My perfect machine would be 3081 (I want fp as you probably heard ;-) )
either on board frame buffer (side note: dec has a good paper on smart frame 
buffers), or VESA slot, SCSI-II, and either ISA, or ethernet. 

Oh yeah why so many sim slots?  I have hit the limit at 8 slots
(with 8 MB) and then upgraded to 16 MB in 4 slots.  I can see 16 slots
but why more? 16 MB is around $400 anyone planning to spend more then
$1600/64 MB for a mips machine running a linux derivative without a second
level cache?

Anyone have any idea how much money/board design is saved by the "integration"
of the 3051/3052 and 3081?  I.e. how much hard would it be to put in a chip 
that lacks such integration?  I.e. say I call motorolla tomorrow any they say 
we will ship some prerelease derated 40 Mhz (from 50 Mhz) powerpc chips for $200
a piece.  What would the cost of using a standard nonintegrated chip over a 
integrated/embedded chip?  I believe the price of the powerpc is expected
to be $320 or so for 50 Mhz (to fast but would probably work at 40), and
$400 at 66 Mhz.

Hmm another bossibiliy is a cheap non fpu processor that has bus snooping,
I think the 486 sx fits the description.  This probably isn't feaible 
and besides it's a INTEL chip (yuck)

I post if detailed summary of the powerpc if anyone wants.  Okay enough
rambling from the sleep deprived....

-- 
Bill                                    1st>    Broadley@neurocog.lrdc.pitt.edu
Broadley@schneider3.lrdc.pitt.edu <2nd  3rd>                 Broadley+@pitt.edu
Linux is great.         Bike to live, live to bike.                      PGP-ok


 

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