Re: Second Sight....

[philip@labtam.oz.au (Philip Stephens)]

Orion Pax writes:

>Uh, I think that 20 mhz number is a misnomer.  What would be more accurate
>is how many pixels it can shovel around in X time.

  The specs that Jawaid posting gives the transfer of one byte at 6 clock
cycles, giving a rate of about 3.3 Mb per second.  Aparently you can also
configure the VGA controller to perform read/modify/write operations on VRAM,
which allows the Z180 code to be simpler, giving you a transfer rate of about
5 Mb per second.
  If you're trying to blit pixels onto a 320x200x256 screen (64K) then
you'd be able to acheive up to 80 fps :-)  Of course, the real rate will
be lower with all the additional processing that typically needs to be done,
but that still makes a 24 fps rate very feasible indeed.

>This sounds pretty good since 320x200x256 uses about 64k of memory.  Plenty
>of memory to store up texture maps, sprite maps, etc.

  Precisely!

>Uh, anybody know how much program code space is available for the Z180?  It
>would be silly to give it say 256 bytes of operating space. :)

  I may be barking up the wrong tree here, but I assume that Z180 code is
actually stored in VRAM; I don't think the SecondSight has a seperate memory
bank for code.

=========== Philip Stephens, Systems Programmer, Labtam Australia ============
====== Owned by Motor (Mo for short), the power-purrer from Down Under =======
== DS (B+S+O+W)t Y 2.5 X  L W C+++ I T++ A+ E H++ S+ V+ F Q++ P B PA+ PL+++ ==
"Many views yield the truth.  Therefore, be not alone." -- Viggies' Prime Song