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Re: [colorforth] ForthBox and FPGA (was: Ideas)


On 2 Mar 2004, at 01:23, Samuel A. Falvo II wrote:


On Monday 01 March 2004 05:02 pm, Luis wrote:

How well documented are the 'older' PCI graphics cards? I was thinking


Not very.


Ok...




a homebrew terminal of sorts, which would need the PCI interface, psu,


That's the key -- you need a PCI interface in this case.  The PCI
interface is hopelessly expensive for a homebrewer to implement. You're 
actually much better off going with a Soekris box and using their PCI
interface.  They already have the relavent chipsets, and the board as a
whole is less than $150 last I recall, including CPU.
Now I recall borrowing a book on this, quite a hefty tome, not quite the 'handbook' I had expected! 
Promptly returned in the hope for something easier...




keyboard/mouse (I am unsure as to how you'd get it to 'boot' off the
ROM in the card, if at all possible).


You know when you boot up your computer, and it always seems to "know"
what video card you have?  That's because *the* very first thing that
happens is the video ROM is executed.  It patches the INT 10h BIOS
vector, and a few other BIOS memory settings.  Then it sets up the
default video tables and sets the default video mode, which BIOS uses
for the rest of its boot-up process.
Hooking into the video ROM is the #1 way to circumvent literally *all* of 
the remaining BIOS initialization sequence.


Well, that's _one_ plus point.




These older graphics cards can be picked up quite cheaply and would
Assuming you can still find them. None of my local computer stores carry 
them anymore.
Locally I can find a few. There's a couple of second hand PC shops not too far from me. Surely the graphics boom has left a large legacy of these lying about? There's always Ebay! 




take care of a lot of the VGA/display overheads.
There's quite a bit of memory on these things too, mostly they come in
at 32MB, but I don't know how big their flashable ROMs are.


Actually, you'll have to deal with the VGA overheads big time.  The
microprocessor cannot read/write from this memory while the video
refresh is occuring, so you'll *still* get 25% to 50% performance.

Modern video card performance is predicated on having distinct memories
for the CPU and for the video card/GPU.


Just shows how aware I am of the internals of these things!




I feel that, whatever the system, it should reflect modern
trends and still be within reach. Maybe ARM is the way. It's a case of


Those SX chips are basically PIC chips (maybe with a different
instruction set, but the same basic idea).  PIC chips can be had for $1
per, in units of 1.  PIC chips have horrid interrupt processing
capabilities though, so maybe the SX chips are better, I don't know.
Last I saw they were fairly basic, they were expounding the software side to them ('virtual hardware' I think was mentioned). 



But there again, notice that these packages are all in PQFP packages.
PIC chips can be purchased in DIP form factor, thus making them easy
(trivial even) for a homebrewer to use.  Indeed, that is largely the
reason for their *wild* success in the amateur radio community.
I ask you now: take out your computer's motherboard. Look at most of the 
chips on the motherboard.  Look at how *close* those pins are.  Would
YOU like to solder those by hand?
Oh no, I'm still recovering from the burns I got from picking up a glass casserole dish straight from the oven (the mitt was on the other hand... I was in a hurry :) Reflow ovens are far too expensive for this type of project. I have made solder filings mixed in with some thinned epoxy, dabbed onto the QFP pins. The IC then got carefully wrapped in a few layers of tin foil. Once placed I heated it up with a gas soldering iron with the hot air attachment on full blast. Ok, so it didn't work the first time, I blew the foil off with the hot air, but after that it's been ok. Even this may be too much for the absolute novice (I classify myself as a novice). Standard electric irons would be cheaper too. Surely there are modern IC's in DIL packaging?! The PIC to name one, there's sure to be more. 



These chips in these form factors are simply not homebrew friendly,
unless you are quite advanced in your knowledge of how to solder.  Most
people who expressed interest in the ForthBox so far in the #Forth
channel literally haven't even built even *one* electronics project in
their life, let alone something that requires soldering 144-pin packages 
with 25 mil pin spacing.

I simply lack the time to be able to assemble the devices myself.
Therefore, it's critical that the device be easily kit-able for those
who wish to *build* one.


Agreed.




I'm willing to donate a website to the project (www.m-i-s-c.net)
whichever form it ends up reaching (z80, 6502, PCI cards, whatever)
and email addresses at the site to discuss and publish ideas. I've got
200MB for email/webmail accounts, so I can divvy that up into 20x10MB
accounts or 40x5MB accounts.


I don't think this is really necessary, but thanks for the offer.  I
already have webspace that I pay money for, so my projects will remain
there.



NP.
The site was to be misc oriented, with the project thrown in as a practical. I see I sounded like it was specifically for the project, but my initial intention for the site was misc in a broader sense. 

Cheers,

Luis.



--
Samuel A. Falvo II


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