Re: Second Sight

["Sheldon Simms" <sheldonsimms@yahoo.com>]

On Thu, 29 May 2003 01:28:33 +0000, Bill Garber wrote:

>>> Did anyone notice that the second sight card on eBay went for $550?
>>> I wonder how many people could/would pay $100 - $200 if someone
>>> could make something similar?
> 
> I was very disappointed that I couldn't afford that much.
> I would have utilized all of that included info, substituted
> a much better video processor than the el'cheapo Oak chip
> they used and attempted to make it display most if not all
> of the IIgs modes.

I've been thinking about this and I don't see much point in
making *just* another VGA card for the Apple II. I have a
better idea...

Consider a second sight card, it's basically a small computer
with a VGA output. The Z180 processor watches the Apple II
bus and emulates writes to Apple II video memory in it's own
VGA video memory. One problem with the second sight card is
that the Z180 is barely powerful enough to do this. Another
problem is that it is difficult to correctly implement things
like scan line interrupts.

What happens if you replace the Z180 with a more powerful
processor, like an Intel 80200 XScale processor at 600Mhz for
example? Then you suddenly have a lot more than a VGA video
card, you have an accelererator card too: All you have to do
is write a 65816 emulation in assembly language, and use that
to replace the hardware 65816. I'd be willing to bet that the
effective speed would average at least the equivalent of a
50Mhz 65816.

Video emulation could be done at full XScale speed because the
Apple II bus would be removed from the video emulation process
and since there would be some extra memory, you would
effectively "cache" the entire Apple II memory space - i.e.: no
external memory would be required at all. Emulating fill modes,
scan line interrupts, and so on would be easy, since the card
would control the scan lines itself. In fact, there would be no
need for the emulated Apple II scan lines to correspond to real
hardware VGA scan lines at all, the entire raster scanning
process can be emulated. In short, one card would replace
three: Zip/Transwarp, Second Sight, Memory Expasion.

The software is fairly simple, I have already done something
similar in my Apple IIe emulator. The biggest problem is the
price. Without some kind of quantity, it would probably be too
expensive. By looking around on the net, I've found following
prices:

Intel 80200 600Mhz                     $65.91
Intel 80312 (PCI, DRAM controller)     $57.67
Asilant 65550 VGA Controller           $28.57
32 Mb PC100 SDRAM                      $5.00
                                     ---------
                                      $157.15

for the main components. Of course, these are mostly prices
for single component purchases, and there might be some cheaper
replacements for the 80312 and the 65550 but if you add glue
components, analog components, circuit board, manufacturing,
etc. It will add up quickly.

The last problem is power. I have be assuming an XScale processor
because you get a lot of computing power for very low power
requirements. Still, it is a 600Mhz processor and the card might
end up being too much of a power hog for an Apple II. For people
who are a little more knowledgeable about the electrical side of
things than I am, the 80200 at 600Mhz has a maximum current
requirement of about 600mA and dissipates 1W with a core
voltage of 1.3V and a periphery voltage of 3.3V.

-Sheldon