🚀 go-pugleaf

cmcmanis%pepper@Sun.COM (Chuck McManis) writes:
>Hmmm, the whole graphics capability question is really foggy so far.

Here's some really straight scoop about the TT from inside Atari:

The video palette has *4* bits per gun for color values.  That is, you
have a total of 4096 colors: 16 levels each of red, green, and blue. 
(The ST has a palette of 512 colors: 8 levels for each gun.)  Another
"color" mode provides 256 levels of grey (actually green), for really
fine reproduction of a black-and-white image.  This is independent of
the resolution: if you're in a 16-color mode, you can pick any 16
levels from the spectrum of 256.  (We call this hyper-monochrome:
one color, but a lot of it!)

There are *6* video modes: the three ST modes (totally compatible),
plus 640x480 16-color, plus 320x480 *256* color, plus 1280x960
monochrome.  ALL of these modes except the last can be shown on a
single monitor.  That monitor need not be multisync.  It can be a
slightly modified VGA monitor, or (of course) the monitor which Atari
will sell for the TT.  The last mode needs a Viking monitor or
something similar.

ST high rez (640 x 400 x 2 colors) is not limited to black and white:
you can choose any two colors.

>Does this mean it has a "DMA" port like the 520/1040/MegaX ? Does it have
>a "real" SCSI port as well? What kind of through put can be expected from
>the hard disk interfaces? Can it do DMA and access > 4Meg ?

Yes, there is a DMA port like on the ST and Mega.  Your hard disk will
plug right in.  You can connect a bootable SH204 and it will boot!
There is also an external SCSI port.  The SCSI port can access the full
32-bit address space; the ACSI port is limited to 24-bit addresses. 
The internal hard drive is connected to the SCSI bus.

>Is the
>VME slot the _only_ way to expand it, or does it have a Mega compatible
>expansion connector as well?

There are a number of ways to expand the TT: you can add 2MB of
dual-purpose (video and CPU) RAM, or 10MB when 4Mbit chips are
available.  You can add 4MB of REALLY FAST 32-bit nybble-mode RAM (not
video-capable), and there's the VME bus.

The number 2MHz that's been bandied about needs some explanation: The
CPU and memory clock speed is 16MHz.  There are four clocks in a bus
cycle.  For dual-purpose RAM, around half the bus cycles go to the 
video or refresh.  Therefore, the CPU gets around two million MEMORY
ACCESSES per second, or 2MHz.  There are other architectural details
which make it a little faster than that.  And remember, each access
gets you 32 bits, not 16 as on the ST.  Also, since the CPU is
allocated half the bus cycles, it isn't ALWAYS postponed by video or
refresh: it might try to access the bus just as its turn comes up, and
not wait at all.  Therefore dual-purpose memory accesses run at MORE
THAN 2MHz.

"Fast" RAM does not have video taking up any of the cycles, so you
don't have to wait for that.  It takes 4 or 5 clocks (I think) to set
up a fast-RAM access, but "nybble mode" means that the CPU fills its
cache in "burst mode" at one cycle per subsequent access.

The VME logic introduces one wait state, so a VMEbus access takes 5
clocks. (Your mileage may vary: VME cards vary widely in response
time.)  But, again, you won't be held off the bus by video.  VME in the
TT shown in Germany is A24/D16 (24 bits of addess, 16 bits of data).

>[programs can load in fast RAM or dual-purpose RAM]

By a "loader option" the original poster means "load program off disk"
not "load .o files into a .prg file."  This is correct: there are flags
in the PRG header which control the behavior of Pexec and Malloc.  Most
program can run in fast RAM -- programs which change the screen base
pointer and some other things can't, though.

>[RAM on the VME bus]

You *can* put memory on the VME bus.  The performance penalty is not
bad.  TOS will recognize that memory and use it for programs if you set
it up right.

>Does it have a Blitter ?

No need for one.  The reason for the Blitter is to remove instruction-
fetch overhead from memory operations, and with the 68030 on-chip
cache, the TT does just fine without it.

>>It is the cheapest workstation of that power around (about 1/2 the price
>>of comparable competitors here in Germany).

You can say that again.  Please, people, remember that when you compare
the TT with a Next machine, for instance, you're talking about roughly
4x the price!  JT's motto is Power Without the Price, and we think
we're giving you just that.

============================================
Opinions expressed above do not necessarily	-- Allan Pratt, Atari Corp.
reflect those of Atari Corp. or anyone else.	  ...ames!atari!apratt