riscy
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Re: Long ramblings about project design

To: riscy@pyramid.com
Subject: Re: Long ramblings about project design
From: caret@pyramid.com (Neil Russell)
Date: Fri, 25 Jun 93 11:39:44 PDT
In-reply-to: <199306251032.AA13175@caesar.cs.Colorado.EDU>; from "Drew Eckhardt" at Jun 25, 93 4:32 am
> From drew@caesar.cs.Colorado.EDU Fri Jun 25 03:33:16 1993
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> To: riscy@pyramid.com, Bill Broadley <broadley@neurocog.lrdc.pitt.edu>
> Subject: Re: Long ramblings about project design 
> In-Reply-To: Your message of "Fri, 25 Jun 1993 04:47:56 CDT."
>              <9306250848.AA21198@gossip.pyramid.com> 
> Date: Fri, 25 Jun 1993 04:32:37 -0600
> From: Drew Eckhardt <drew@caesar.cs.Colorado.EDU>
> 
> 
>     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?
> 
> Might not be possible - there isn't a lot of realestate available on an 
> ISA board.

Actually, I had already designed this for the most part.  There was rom
for about 16 SIMM sockets, CPU and support logic, with soom to spare.

>     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).
> 
> Another poster suggested that  TI32010 can be had for $20, add
> cost of the RAMDAC + either DRAM (about $20/meg) or VRAM (two-three times 
> DRAM price).

That's TI 34010.  If that's the way we went for video, you must use
VRAM and require a RAMDAC of some sort.  Some very rough guesses would
give $25 for the 34010, 20 for the RAMDAC and $80 for the VRAM.  This
is a little more expensive than what I wanted but still well below
the cost of a similar plug in card.

> Nasty timing problems acompany any high speed bus, and since we aren't 
> Pee-Cee compatable VESA might not be that easy.

At the moment I can't see much justification for such a bus;  doing the videooo
ourselves seems like a much easier and surer path.

>     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 
> an

Just for the record, the TI34020 is much more expensive than the TI34010.
Both are software compaible (fr the most part).  The TI34020 is also
much harder too interface with than the TI34010.  The only thing the new
chip ooffers is extra speed.

> You can allways use just a minimal amount of intelligence, ie treating
> it as a dumb frame buffer if possible, or just doing bitblts with it until 
> you get arround to doing a "propper" driver..

Yup; Also, no one says that you have to use TIGA.  There are C compilers
that can you can get t handle this chip.  BTW, there have been attempts
t port GCC too the TI340?0 without much success; the TI340?0 are bit-
adressable machines; GCC makes tooo many assumptions that its compiling
for a byte addressable machine.

>     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 
> sin
>    ce 
>     we have fast int cpu).  

I'm almst sure that ethernet will cost us about half of an ISA card.
I certainly do want ethernet, and figure that more than half of us
do also.  When we have some more concrete figures we can make better
judgements.

> I'm begining to wonder about the need for the ISA bus - 

If we don't have an extension bus of some sort then haven't we
painted ourselves into a corner?  What about the guy who needs just
that extra serial port, or has a printer that can handle 10 times
the speed using parallel (me), other small buletin board service
that needs those 16 modem contrlled, dumb serial ports?

> Pros : we can put nifty things like ROM burners in the ISA slots, and
>       parallel printer/floppy controllers.
> 
> Cons :  the ISA slots take up lots of realestate (not just 
>       for the connector - we could have clearance problems with 
>       heat sinked chipps and SIMMs)

There are few useful ISA cards that require the full length of the box.
The boards I mentioned above are all short boards.  In any case
I think we could deal with that problem, maybe by increasing the size
of the board too get that suff away from there.  How many people
think that a mini-case is a requirement?

> How hard would it be to put a floppy controller and parallel port on
> the mainboard compared to putting in a full ISA bus?

Probably not hard, but there is no cost justification, when there is
an ISA bus.

>     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?
> 
> Memory interleaving.  You use more, smaller chips so that you can 
> interleave memory accesses to them, cutting wait states by a factor 
> of two for two-way for sequential accesses on a cache miss, four 
> by four-way.  In order two take advantage of interleaving,
> you need to fill two or four banks at a time.  
> 
> Hmm - I know our chipset supports 2-way interleave, does it support 
> way?  And what about page mode?  

It nly does 2-way interleaving.  Yes it does page mode.  But the main
reason for the extra SIMM sockets is expansability.  Remember that
MIPS binaries are *large*.  Als, since this is a fast machine with reasonably
good I/O, there is a good chance that it could get used for a many
user machine.  If those users run X, then 128M becomes small.

>     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.
> 
> Wow! a volunteer to do the GNU ports of GCC and GDB to the PowerPC =8^)
> 
> We'd also need support chips (availability and cost?), and would have to
> work arround hardware bugs in the chip (ie, early 386's that didn't 
> run in protected mode, the 68040 with broken transcendental functions,
> etc).

He has a point.  At least the chips we are currently planning to use
have had good field testing.

> Since we have the tools, the SPARC might be worth looking at.

I figured that the MIPS was just that little bit cleaner than the SPARC.
It may be worth looking that though; they seem to be going for similar
markets.  On the other hand I'd prefer to deal with IDT than Sun.

>     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)
> 
> The solution we're looking at right now would be competitive with a 
> 486DX2-66 in terms of both price (I can get a 486DX2-66/64K secondary 
> cache VESA local bus mainboard for $610 (Of course, this doesn't include 
> video (say $150), SCSI (say $200), ethernet ($80), 16550's, etc)) and 
> performance (integer performance is very comparable, floating point 
> is as much as 5X as much).  

If everyone just want's anther x86 motherboard, I'll give up right now.
Apart from the purely asthetic arguments, there are cooompanies that
can do x86's at *much* better prices than we could ever hope to match.

-- 
Neil Russell            (The wizard from OZ)
Pyramid Technology                      Email:  caret@pyramid.com
3860 N. First Street                    Voice:  (408) 428-7302
San Jose, CA 95134-1702                   FAX:  (408) 428-8845

 

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