1.2.135 FLICKER SEEN WHEN USING XGA DISPLAY ADAPTER IN 1024*768 MODE
- From: Louis Ohland <ohland@xxxxxxxxxxx>
- Date: Wed, 07 Nov 2007 19:10:00 -0600
Record number: H091339
Device: D/T8550
Model: M
Tip key: 086
Date created: O91/07/10
Date last altered: A92/07/27
IF FLICKER IS EXPERIENCED WHEN RUNNING CUSTOMERS SOFTWARE, BUT
THE XGA ADVANCED DIAGNOSTICS RUN ERROR-FREE, THE DISPLAY AND
THE XGA ADAPTER ARE FUNCTIONING CORRECTLY AND NO HARDWARE SHOULD
BE REPLACED. HOWEVER, A MIS-MATCH BETWEEN THE SOFTWARE AND THE
DISPLAY VIDEO BUFFER SIZE SHOULD BE SUSPECTED.
FLICKER EXPERIENCED DURING SYSTEM OPERATION MAY BE CAUSED BY
EITHER A MIS-MATCH BETWEEN THE SOFTWARE AND THE XGA HARDWARE
CONFIGURATION, OR PROGRAMMING WHICH USE DISPLAY MODES/COLOR
PATTERNS THAT CAUSE THE FLICKER EFFECT.
SOFTWARE IS MORE LIKELY TO "FLICKER" WITH 512K BYTES OF VIDEO
MEMORY (VRAM) THAN IF THE FULL 1M BYTE OF VRAM IS INSTALLED (SEE
ADDITIONAL INFORMATION BELOW FOR DETAILS). IN THE USA, THE
XGA ADAPTER COMES WITH 512K BYTES OF DISPLAY VIDEO MEMORY
INSTALLED. AN ADDITIONAL 512K BYTE OPTION IS AVAILABLE AT EXTRA
COST.
**************************************************************
BECAUSE DISPLAY SUB-SYSTEMS ARE SOFTWARE DRIVEN OUTPUT DEVICES,
THEY ARE SUBJECT TO EXHIBITING UNEXPECTED RESULTS DUE TO
PROGRAMMING AND/OR CONFIGURATION ERRORS. FOR THIS REASON, ONLY
THE ADVANCED DIAGNOSTICS ARE VALID TO DETERMINE THE PROPER
FUNCTIONING OF ANY PS/2 DISPLAY SUB-SYSTM.
**************************************************************
DIAGNOSTICS DETAILS:
THE XGA ADVANCED DIAGNOSTICS WILL DETERMINE THE AMOUNT OF VIDEO
MEMORY INSTALLED, AND TEST IT APPROPRIATELY. IF AN ERROR IS
DETECTED ON THE FIRST 512K OF VIDEO MEMORY (VRAM). THE ENTIRE
ADAPTER MUST BE REPLACED, AS THIS BLOCK OF MEMORY IS SOLDERED
TO THE ADAPTER. IN THE SECOND 512K OF VRAM, THE DIAGNOSTIC
CAN DIAGNOSE ERRORS TO A SINGLE FAILING 128K MEMORY MODULE,
AS THEY ARE INSTALLED IN (4) PLUGGABLE CONNECTORS. ALL FOUR
PLUGGABLE CONNECTORS WILL BE POPULATED ON A 1MB VRAM XGA
ADAPTER.
THE XGA VIDEO MEMORY FRU, P/N75X5894, PROVIDES ONLY ONE 128K
MODULE.
IF AN ADDITIONAL 512K OF VRAM MEMORY CORRECTS THE "FLICKER,"
MARKETING ASSISTANCE SHOULD BE SOUGHT, AS THIS ADDITIONAL
MEMORY IS AN EXTRA CHARGE OPTIONAL FEATURE.
************** ADDITIONAL INFORMATION ***********************
IF 1 MB OF VIDEO BUFFER IS INSTALLED AND FLICKER STILL
EXISTS USING SOME COLORS OR PATTERNS, THE FOLLOWING
INFORMATION MAY BE HELPFUL.
THERE ARE TWO TYPES OF FLICKER EFFECT:
A. FULL SCREEN FLICKER
THIS TYPE OF FLICKER CAN BE OBSERVED IN NON-INTERLACED
MODES. IT IS CAUSED BY THE SCREEN REFRESH RATE BEING
SLOW ENOUGH TO BE DETECTABLE BY THE USER. INDIVIDUALS
VARY WIDELY IN THEIR ABILITY TO SEE FLICKER, YOUNG
PEOPLE BEING MOST SENSITIVE.
B. INTERLACE FLICKER.
INTERLACE MEANS THAT A FULL SCREEN PICTURE (A "FRAME"
IS REFRESHED IN TWO "FIELDS", THE ODD SCAN LINE "FIELD"
AND THE EVEN SCAN LINE "FIELD." WHEN THE FRAME IS
REFRESHED, ALL THE ODD SCAN LINES (1,3,5 ETC.) ARE
DISPLAYED, THEN ON THE NEXT FIELD ALL THE EVEN SCAN
LINES (2,4,6 ETC.) ARE DISPLAYED, THIS METHOD OF
REDUCING FULL SCREEN FLICKER IS USED IN TELEVISION SETS.
XGA DETAILS:
XGA SUPPORTS SEVERAL DISPLAY MODES. THEY ARE LISTED
BELOW WITH THE APPROPRIATE SCREEN REFRESH INFORMATION:
VGA MODE ___________________________(60 OR 70 HZ NON-INTERLACED)
132 COLUMN TEXT MODE________ _______(60 HZ NON-INTERLACED)
EXTENDED GRAPHICS MODE(640*480)_____(60HZ NON-INTERLACED)
EXTENDED GRAPHICS MODE(1024*768)____(43HZ INTERLACED)
ONLY THE 1024*768 RESOLUTION IS INTERLACED AND SUBJECT TO
FLICKER. ALL OTHER MODES ARE NON-INTERLACED AND HAVE THE
SAME SCREEN REFRESH RATES AS VGA.
THE SIZE OF VRAM PROVIDES MODE COLORS AS CAN BE SEEN BELOW:
1. 512K VRAM, PROVIDES:
- 640*480 RESOLUTION WITH 256 COLORS.
- 1024* 768 RESOLUTION WITH 16 COLORS.
NOTE:
WITH 512KB OF VRAM INSTALLED, THE SMALL NUMBER OF COLORS
AVAILABLE FOR EACH PEL (16) IN 1024*768 MODE RESULTS IN A
POSSIBILITY OF FLICKER.
2. 1MB VRAM, PROVIDES:
- 640*480 RESOLUTION WITH 65536 COLORS (NOT AVAILABLE
USING THE XGA DEVICE DRIVERS, 256 COLORS STILL (AVAILABLE)
- 1024*768 RESOLUTION WITH 256 COLORS.
NOTE:
AN UPGRADE OF THE XGA TO ITS FULL 1MB OF VRAM WILL INCREASE
THE NUMBER OF COLORS AVAILABLE TO 256, GREATLY REDUCING THE
FLICKER EFFECT POSSIBILITY.
3. IF BOTH 1 AND 2 ABOVE, ARE NOT ACCEPTABLE, IT IS NOT
NECESSARY TO REVERT BACK TO VGA MODE, WHICH IS LIMITED TO 16
COLORS. THE XGA EXTENDED GRAPHICS (NON VGA) MODE HAS 640*480
RESOLUTION AND IS NON-INTERLACED. IT PROVIDES 256 COLORS PER
PEL, IS SIGNIFICANTLY FASTER THAN VGA MODE AND HAS ALL THE
OTHER XGA BENEFITS.
NOTE:
EVEN WITH THE 1MB OF VRAM INSTALLED, FLICKER MAY RESULTS
IF A USER SPECIFIES A PATTERN WHICH HAS BRIGHT PELS ON
ONE FIELD AND DIM PELS ON THE OTHER. A BLACK AND WHITE
CROSSHATCH PATTERN IN AN APPLICATION OR A BACKGROUND
BITMAP, FOR EXAMPLE, MAY HAVE THIS EFFECT.
IF THE USER HAS AN ABSOLUTE REQUIREMENT TO USE A PATTERN
WHICH CAUSES UNACCEPTABLE FLICKER, THEN THE CURRENT, BEST
XGA SOLUTION IS TO REVERT TO OPTION 3 ABOVE (NON VGA MODE).
.
- Prev by Date: Type 0 touchup
- Next by Date: 1.4.30 UNSUCCESSFUL 50 MHZ PROCESSOR INSTALLATION
- Previous by thread: Type 0 touchup
- Next by thread: 1.4.30 UNSUCCESSFUL 50 MHZ PROCESSOR INSTALLATION
- Index(es):
Relevant Pages
|
