[comp.sys.mac] Mac II Video Glitches

viking@iuvax.UUCP (Jon W. Backstrom) (10/30/87)

Has anyone else noticed small horizontal bars about 2-3 pixels from the
top of the screen when using the 256 color mode on Apple's Mac II video
card?  I thought this was something specific to my system (blown memory
on the video card or something), but now I've seen it on three other
Mac II displays.

I didn't notice it until I upgraded the Mac II to 5 Mb of memory.  After
that, if I used *any* video mode with more than 2 colors, I get an
interesting video artifact...

A CLOCK!!  If I use the 4 color mode, I can see a tiny clock with full
hour:minute:second format.  As you progress to 16 and 256 colors, the display
simply looks 'gliched'.  I tried removing "Menu Clock" from the system folder,
thinking it was a bug from that program but that wasn't it.

What is it?!  Has anyone else seen this phenomenon?


-------------------------------------------------------------------------------
|  Jon W. Backstrom             "Yah sure...we gonna have fun, you bet!"      |
|  Computer Science Department                                                |
|  Indiana University           UUCP: {ihnp4,pyramid,rutgers}!iuvax!viking    |
|  Lindley Hall 101             ARPA: viking@iuvax.cs.indiana.edu             |
|  Bloomington, IN  47405                                                     |
|                               "The world has arrived at an age of cheap     |
|  (812) 335-2849 (Office)       complex devices of great reliability; and    |
|  (812) 336-3660 (Home)         something is bound to come of it."           |
|                                                 - Vannevar Bush (1945)      |
-------------------------------------------------------------------------------

lsr@apple.UUCP (Larry Rosenstein) (11/02/87)

In article <4222@iuvax.UUCP> viking@iuvax.UUCP (Jon W. Backstrom) writes:
>
>I didn't notice it until I upgraded the Mac II to 5 Mb of memory.  After
>that, if I used *any* video mode with more than 2 colors, I get an
>interesting video artifact...
>
>A CLOCK!!  If I use the 4 color mode, I can see a tiny clock with full

This indicates a program that is writing directly to the screen.  The your
monitor is set of more than 2 colors/grays, then the code which writes
directly to the screen will not work properly because the display memory is
organized differently.  

You will see this effect in other places (eg, MacPaint).  Until the
offending program is updated, there is nothing you can do but change your
screen to 2 color mode.



-- 
Larry Rosenstein

Object Specialist
Apple Computer

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

waltervj@dartvax.UUCP (walter jeffries) (11/04/87)

In article <4222@iuvax.UUCP> viking@iuvax.UUCP (Jon W. Backstrom) writes:
>:
>A CLOCK!!  If I use the 4 color mode, I can see a tiny clock with full
>hour:minute:second format.  As you progress to 16 and 256 colors, the display
>simply looks 'gliched'.  I tried removing "Menu Clock" from the system folder,
>thinking it was a bug from that program but that wasn't it.

I got that with Jclock on our MacII.  Make sure it is not in the System folder
or the System itself.
-Walter.