[comp.sys.mac] Video memory and the Mac II

hunt@firqb.dec.com (Phil Hunt) (10/12/87)

Hello,
 
   I was wondering how the Mac II video memory lays out.  In other words, how
do they make old pgms compatible with the new memory map??   I know the video
display card now contains memory for the display.  But that memory is not 
counted in the system size memory!!  Is the video memory now ABOVE mem max
for the system???  How does it work....???
 
   Also, I have found some old pgms (1984-1986) that run IN COLOR. The old
Cricket Graph 1.0 (Yes, 1.0!!) runs on MY MAC II in COLOR,  so does some
card games.  The diamonds and hearts are in color!!!   Is this a maaping 
between othe old Quickdraw 8 color (IE IM II mapping) and the new CQD???
 
Phil Hunt

Mark_Peter_Cookson@cup.portal.com (10/21/87)

Yes, you are right.  The old quickdraw does have the 8 colors that the Image-
Writer II will print.  Most programs didn't use them as there was no way to
see them on a 128-SE, but I guess they were thinking ahead.  The only diffenece
between the old and new QuickDraw is that the new has access to 16 million
colors at 256 at a time.  As to your other question, I think that the memory
on the card is used by the card as I am sure that the vidio output comes out
of the CARD and not the II.  So the II has no use for the memory since it just
tells the card what to do and it does all the memory stuff that is needed.
I am rushed for time, but I hope I answered your question.

Mark Cookson

(From Portal in Cupertino!  Home of Apple!!!  Even though they lost $11 Mon
we still love them, right?)

gwe@cbdkc1.UUCP (10/22/87)

In article <1049@cup.portal.com> Mark_Peter_Cookson@cup.portal.com writes:
>see them on a 128-SE, but I guess they were thinking ahead.  The only diffenece
>between the old and new QuickDraw is that the new has access to 16 million
>colors at 256 at a time.  As to your other question, I think that the memory
           ^^^^^^^^^^^^^

Correct me if I am wrong, but I thought the new color quickdraw would work
for a full 24-bit plane system ... The 256 color-at-a-time limitation is a
limit of the current Mac II video card technology. I thought that SuperMac or
someone was working on a full 16 million color system using 3 of their 8-bit
color cards.

-- 
George Erhart at AT&T Bell Laboratories Columbus, Ohio 
614-860-4021 {ihnp4,cbosgd}!cbdkc1!gwe

lsr@apple.UUCP (Larry Rosenstein) (10/23/87)

In article <11827@decwrl.DEC.COM> hunt@firqb.dec.com (Phil Hunt) writes:
> 
>   I was wondering how the Mac II video memory lays out.  In other words, how
>do they make old pgms compatible with the new memory map??   I know the video

Most application do not deal directly with screen memory, and are
insensitive to where it is located.

Some application do write directly to screen memory, but examine the
Quickdraw data structures to see where it is located.  Such application
won't work on a Mac II unless the screen is set for 2 colors.  (The symptom
of this is seeing a bunch of tiny images at the top of the screen.)

>   Also, I have found some old pgms (1984-1986) that run IN COLOR. The old
>Cricket Graph 1.0 (Yes, 1.0!!) runs on MY MAC II in COLOR,  so does some
>card games.  The diamonds and hearts are in color!!!   Is this a maaping 
>between othe old Quickdraw 8 color (IE IM II mapping) and the new CQD???

Color Quickdraw supports the old Quickdraw color model of 8 fixed colors and
maps those colors into the closest available color..

Larry Rosenstein

-- 
Larry Rosenstein

Object Specialist
Apple Computer

AppleLink: Rosenstein1
UUCP:  {sun, voder, nsc, mtxinu, dual}!apple!lsr
CSNET: lsr@Apple.com

jww@sdcsvax.UCSD.EDU (Joel West) (10/23/87)

In article <6537@apple.UUCP>, lsr@apple.UUCP (Larry Rosenstein) writes:
> Color Quickdraw supports the old Quickdraw color model of 8 fixed colors and
> maps those colors into the closest available color..

I don't want to get picky (particularly with Larry), but
Color QuickDraw actually:

     *	maps the eight using 'clut' resource #0, which stores
	colors that approximate the ImageWriter II output
     *	then chooses the nearest available color from the 
	display's color table

With the 256-color video board, there's a noticeable difference
between these 8 colors and the fully saturated, pure eight:

	white
	red
	yellow
	green
	cyan
	blue
	magenta
	black

Of course, the IW II ribbon only supports cyan, magenta, yellow
and black, so the other colors (except white) are produced
by two-color combinations.

We put two orthogonal plots of this 8-color clut in an HSV (Hue,
Saturation, Value) cone in the Colorizer manual, and it turns
out that both the saturation and value for green are way off.
Also, magenta is reddish and cyan is bluish, so the IW II
manual calls these "purple" and "blue".
-- 
	Joel West  (c/o UCSD)
	Palomar Software, Inc., P.O. Box 2635, Vista, CA  92083
	{ucbvax,ihnp4}!sdcsvax!jww 	jww@sdcsvax.ucsd.edu

Mark_Peter_Cookson@cup.portal.com (11/10/87)

You may be right, I have never come across one that does do a 24 bit plain.
I wish I would.  That would be a sight.  At present, though, all I can see is
256 colors, but by some switching of the colors you can get more than 256 on
the screen at a time.  It is complicated, and I don't quite understand it, let
alone remember it.  If you want details I might be able to find them for you.

Gee, just think, 1 meg of memory JUST for the monitor.  And I though that 22K
was a lot!

Mark Cookson