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

["Samuel A. Falvo II" <kc5tja@xxxxxxxx>]

On Monday 01 March 2004 05:02 pm, Luis wrote:
> How well documented are the 'older' PCI graphics cards? I was thinking

Not very.

> 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.

> 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.

> 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.

> 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.

> 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.

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?

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.

> 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.

--
Samuel A. Falvo II


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