Re: Second Sight....

[bazyar@netcom.com (Jawaid Bazyar)]

jlee@ics.uci.edu (Orion Pax) writes:

>Philip Stephens (philip@labtam.oz.au) wrote:
>:   * 20 Mhz Z180 processor for "blitting" (and undoubtable usable for many
>:     other tasks if programmers are clever enough)

>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.  If it say takes 20
>cycles to shove one pixel around (say 8 bytes) it could end it being
>slightly slow.  Anybody got the cpu stats? :)

  Stop saying "uh" so much, it's annoying. :-)

  With the Z180's built-in DMA controllers, you can move a byte of
data in 6 cycles (3 to read, 3 to write - it's definitely not a
65816). Since the first couple batches of production boards are
running at 18.5MHz, this ends up being approx 3MB/sec that the Z180
can move.

>: doing most of the blitting and texture maps stored directly in VRAM, I
>: believe I can have a 320x200x256 resolution screen rendering at a respectable
>: frame rate.)

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

  Yep. There's all kinds of video RAM available for that sort of thing.
And in fact, even though the Z180 is only an 8-bit processor, 
using special features of the VGA chip it can move 32 bits around
in a single operation, from video memory to video memory.
  The VGA chip also has color-expand and similar features for
fast text and pattern draw (draw 8 pixels, 8 bytes, with a single
8-bit write).

>: great colour and shading, not to mention faster graphics using sprite routines
>: downloaded onto the video board itself.  What more could you ask for?

>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. :)

  At least 64K of SRAM will be available.
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