Re: Second Sight board

[bazyar@netcom.com (Jawaid Bazyar)]

vmbb!pro-newton!pro-dan!danb (Dan Brown) writes:

>I just read through Jawaid's posting on c.b.a2 with questions and answers
>about the Second Sight card, and came up with a few questions and
>observations.  In no particular order:

>        Drew Vogan designed the card.  Cool!  He's been known to do some good
>stuff before...  (Prolly has something to do with why the Z180 was selected,
>too).  How long has the design been done?  Was this something that's been
>sitting on a shelf for a while, or is it a new design?

  It's a new design, done around April.  Yes, it takes a while to
get these sorts of projects in gear :-)

>        Does the shadowing slow down screen displays?  Is it compatible with
>such infamous software as the FTA demos?

  Yes and no. The shadowing is currently running at a reasonable
15 fps. Now, before you get all bent out of shape, let me note that
this does not slow down the IIGS side at all.. it's just the (_Current_!)
maximum rate we can turn 32K of SHR data into 128K of VGA data. There
are several tricks I can pull, one that would at least double or triple
the frame rate, with a few limitations.
  Since the shadowing of bytes is done by hardware, if program X
writes a byte into the IIGS Mega 2 memory, we have a copy of it.

>        The high-resolution text modes sound mondo cool.  Do they support
>attributes other than inverse (bold, underline, etc)?  This could provide the
>foundation for a great VT100 emulator.

  Yep, regular PC-style text.

>        How much would VRAM upgrades cost?  Are the parts available through
>"normal" channels, or would they need to be ordered from Sequential?  In,
>say, the 640x480x256 mode, what would the "left-over" VRAM be used for? 
>Storing other screens and being able to quickly flip between them?

  The VRAM chips are actually standard DRAMs, 256Kx4. Very cheap.

>        Would it be feasible to allow for a 640x480x16.7m mode with 1MB VRAM?

  No.. we'd have to have put a much more expensive DAC on the chip
(maybe even two DACs) and probably used real VRAMs, which are a lot
more expensive.

>        A while ago, the suggestion of an X port under GNO/ME was made, and
>dismissed due (in part) to lack of desktop real estate.  Could that be
>considered again?

  Sure.. if we're willing to wrestle with some other problems. Something
that works like X and could talk to X over Ethernet could be done.

>        Why the requirement that the SS card be in slot 3 on a ROM 01 GS?  Is
>there such a requirement in a //e?

  No, the //e just has the two banks of memory, and we follow which bank
is being used by watching soft switches. 
  The ROM 01 GS has the M2B0 signal only on slot 3, and this signal
is required for the shadowing to work.

>        Does the board require any kind of configuration, or is it "plug and
>play"?

  It's plug and play.

>        Jawaid, this sounds like a really, incredibly cool product.  Post a
>release when it's available, and I _will_ buy one.  Thanks!

  You can place and order right now, if you like.
-- 
 Jawaid Bazyar              |   Like UNIX? Like your Apple IIGS? Then ask
 Procyon, Inc.              |   me about GNO/ME for the Apple IIgs!   
 bazyar@netcom.com          |   P.O Box 620334
 --Apple II Forever!--      |   Littleton, CO 80162-0334   (303) 781-3273