[comp.sys.amiga.tech] Broken Sprite?

roccom@tahoe.unr.edu (RoCCo mArtIn) (05/14/89)

	I've noticed that using certain hacks such as "oing" and "friends"
   creates a character that is smeared vertically across the screen.  I'm
   assuming that these programs are using sprites of some kind.  Could
   someone please let me know what the problem could be???

					Much grass,
					 - Rocco Martin
-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Usenet:      uunet!unrvax!tahoe!roccom
Internet:    roccom@tahoe.unr.edu
Withoutanet: mousketeers@disney.land.fun (ok, so its not very punny ...)

jms@tardis.Tymnet.COM (Joe Smith) (05/15/89)

In article <2254@tahoe.unr.edu> roccom@tahoe.unr.edu (RoCCo mArtIn) writes:
>	I've noticed that using certain hacks such as "oing" and "friends"
>   creates a character that is smeared vertically across the screen.

Go into Preferences and re-center your display.  If the screen is shifted
over too far to the left, it eats into the time allocated to sprites 6
and 7.  It causes the symptoms you describe - a vertical band of random
colors, 16 dots wide and going the full length of the screen.

It's unfortunate that Preferences does not do something when this extreme
setting is selected.  It really should put up a requester saying:

	Warning: Sprites 6 and 7 have been disabled
	   [ OK ]                     [ CANCEL ]

-- 
Joe Smith (408)922-6220 | SMTP: JMS@F74.TYMNET.COM or jms@tymix.tymnet.com
McDonnell Douglas FSCO  | UUCP: ...!{ames,pyramid}!oliveb!tymix!tardis!jms
PO Box 49019, MS-D21    | PDP-10 support: My car's license plate is "POPJ P,"
San Jose, CA 95161-9019 | narrator.device: "I didn't say that, my Amiga did!"

lphillips@lpami.wimsey.bc.ca (Larry Phillips) (05/16/89)

In <2254@tahoe.unr.edu>, roccom@tahoe.unr.edu (RoCCo mArtIn) writes:
>    I've noticed that using certain hacks such as "oing" and "friends"
> creates a character that is smeared vertically across the screen.  I'm
> assuming that these programs are using sprites of some kind.  Could
> someone please let me know what the problem could be???

Run Preferences and move your screen to the right, and a little below center.
With it too far left, you eat cycles that are needed by one of the sprites.
It's a very old problem, and first showed up for me when running MindWalker.

-larry

--
  - Don't tell me what kind of a day to have! -
+----------------------------------------------------------------------+ 
|   //   Larry Phillips                                                |
| \X/    lphillips@lpami.wimsey.bc.ca or uunet!van-bc!lpami!lphillips  |
|        COMPUSERVE: 76703,4322                                        |
+----------------------------------------------------------------------+

ewhac@well.UUCP (Leo 'Bols Ewhac' Schwab) (05/17/89)

In article <2254@tahoe.unr.edu> roccom@tahoe.unr.edu (RoCCo mArtIn) writes:
>	I've noticed that using certain hacks such as "oing" and "friends"
>   creates a character that is smeared vertically across the screen.  I'm
>   assuming that these programs are using sprites of some kind.  Could
>   someone please let me know what the problem could be???
>
	Let me try and make this lucid yet terse so that those who know what
the answer is don't get bored.

	Every video line the Amiga generates is divided into a number of
slots.  In these slots, the custom hardware fetches needed information from
memory to do its thing.  Among these are DRAM refresh, floppy disk DMA,
audio DMA, sprite DMA, and display DMA.

	Now, if you use Preferences start dragging your screen to the left,
display DMA needs to happen earlier so that it can display bits earlier on
the video line.  If you pull the screen far enough left, the display DMA
will start eating up the DMA slots belonging to the other facilities.  The
first to go are the sprite channels, from sprite 7 to sprite 0.
Theoretically, you should be able to stomp the audio channels as well, but I
don't know of anyone who's done this.

	The cure for your sprite troubles is to free up the sprite slots
again by dragging your screen to the right.

	[ Note for picky people:  I have it on reasonably good authority
that the documented hardware stop that's supposed to prevent killing sprite
0 doesn't actually exist. ]

_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
Leo L. Schwab -- The Guy in The Cape	INET: well!ewhac@ucbvax.Berkeley.EDU
 \_ -_		Recumbent Bikes:	UUCP: pacbell > !{well,unicom}!ewhac
O----^o	      The Only Way To Fly.	      hplabs / (pronounced "AE-wack")
"Work FOR?  I don't work FOR anybody!  I'm just having fun."  -- The Doctor

michael@maui.cs.ucla.edu (michael gersten) (05/26/89)

In article <200@tardis.Tymnet.COM> jms@tardis.Tymnet.COM (Joe Smith) writes:
>  [talking about the screen being too far over causing sprite problems]
>	Warning: Sprites 6 and 7 have been disabled
>	   [ OK ]                     [ CANCEL ]

But does it really disable them? It seems that allocation likes to start
at sprite 6 or 7 (not sure which) and work downwards; even cube masters,
which onle uses one or two sprites, dies on an overscan screen (and 
according to the hardware manual, my screen position should only kill
one sprite.)

			Michael