From: hyc@hanauma.jpl.nasa.gov (Howard Chu)
Subject: Re: Blitter - what does it do besides bitcopy?
Organization: SAR Systems Development & Processing, JPL
Date: Thu, 24 Dec 1992 01:00:27 GMT

In article <1gvg4tINNqmm@usenet.INS.CWRU.Edu> aa399@cleveland.Freenet.Edu (Len Stys) writes:
>Hi, all...
>A Blitter is a bitmap copying and transformation chip?
>
>Is this all that it does?

Pretty much. However, "bitmap" is somewhat over-specific. I believe the
Falcon blitter is also used to perform block memory transfers to the
IDE hard drive, just as an example.
>
>Which chip is responsible for the STe's hardware scrolling?

The video shifter chip. All of the STe shifter's capabilities are also
present in the Falcon's video chip.
>
>Most other game systems use a very fast graphics chip to take care of
>the sprites, scaling, scrolling, etc.

The blitter does fine for sprite manipulation. I think it also serves for
scaling (but not certain there). Scrolling is already handled by the video
chip.
>
>My question is:  If ATARI is interested in making this system a competitor
>in the computer entertainment market, why didn't Atari include one?

The Falcon is a home computer that also can play games, not a game system
that happens to contain a computer. Different emphasis, I'd say.
>
>The SNES has a CPU speed of 3.58 MHz!  Everyone looked at this speed
>and laughed, but the graphics chip showed that the speed of the processor
>did not matter too much at all.

Well, a 6502 (er, 65816) is a pretty efficient chip, as microprocessors go.
Almost all its instructions execute in a single clock cycle. In contrast,
the fastest 68000 instructions all take 4 clock cycles, and the average
cycle time is out around 6 cycles. Given this disparity, it's plain to see
that clock speed alone isn't enough to judge anything, and anyone who looks
solely at speeds to judge systems is an outright fool.

>The Sega Genesis is based on a 68000 CPU at the speed of 7.6 MHz.
>This system pretty much relies on the programmer for rotation, etc.
>BUT I'm pretty sure it still has a graphics chip.  And I'm POSITIVE
>that the Sega CD-ROM player has an especially designed graphics chip
>for rotation.
>
>Recently, Nintendo announced to the world that it has developed a graphics
>chip that will be powerful enough for 3-D imaging.
>
>If the Falcon030 does NOT have a graphics chip that is responsible for
>these features, won't the video game systems pass this system by?

Neither the PCs nor the Macs have any hardware-assisted graphics to speak of.
I.e., no blitter, no sprite generator, no fine scrolling either vertically or
horizontally, very limited video memory constraints. Games are written for
these systems all the time. It seems to me that you're being a bit over
concerned about one minor detail (especially when there are so many other
major details to be concerned about, like, when will the Falcons actually
be for sale in the US?)

As a final note, there are already a huge number of arcade shoot-em-up
games on the plain ol' ST, which doesn't even have a blitter. Most of them
look pretty good. What's the problem?
>
>I doubt there is any way that a FUTURE 64-bit RISC graphics chip can be
>added to the Falcon030 at another time...

True enough. The Falcon's memory is only 32 bits wide, after all; what good
would a 64 bit chip be inside there anyway?
-- 
  -- Howard Chu @ Jet Propulsion Laboratory, Pasadena, CA

There's a narrow border between genius and insanity, but I'm a dual citizen.