Browse Prior Art Database

Adaptive Simultaneous Display with Single CRTC for Notebook PC which has Non standard resolution of LCD display

IP.com Disclosure Number: IPCOM000013386D
Original Publication Date: 2000-Feb-01
Included in the Prior Art Database: 2003-Jun-18
Document File: 5 page(s) / 75K

Publishing Venue

IBM

Abstract

With Notebook PC, Graphic accelerator(hereafter video chip) is going to support so called "multi monitor" with dual CRTC in it. This means to support same desktop image on both internal LCD and external CRT with different resresh rate, e.g. XGA with 60Hz on LCD and 85Hz on CRT. Simultaneous display on internal LCD and external CRT can be supported with single CRTC as well, however, in this case, same refresh rate, e.g. 60Hz. on both displays. We have decided to pick up 1400x1050 dot TFT LCD(hereafter SXGA+ LCD) as integrated LCD for 1Q/2000 new ThinkPad. The above dual CRTC has another merit for supporting such as NON VESA standard resolution LCD.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 55% of the total text.

Page 1 of 5

  Adaptive Simultaneous Display with Single CRTC for Notebook PC which has Non standard resolution of LCD display

    With Notebook PC, Graphic accelerator(hereafter video chip) is going to
support so called "multi monitor" with dual CRTC in it.

This means to support same desktop image on both internal LCD and external CRT
with different resresh rate, e.g. XGA with 60Hz on LCD and 85Hz on CRT.
Simultaneous display on internal LCD and external CRT can be supported with
single CRTC as well, however, in this case, same refresh rate, e.g. 60Hz. on
both displays.

  We have decided to pick up 1400x1050 dot TFT LCD(hereafter SXGA+ LCD) as
integrated LCD for 1Q/2000 new ThinkPad.

The above dual CRTC has another merit for supporting such as NON VESA standard
resolution LCD.

If only single CRTC in video chip, simultaneous display can not be supported
since 1400x1050 resolution on CRT is out of VESA spec..

In case of dual CRTC video chip, one CRTC can be used for driving internal
LCD, e.g. SXGA+ and the other can be for external SXGA CRT.

The dual CRTC, however. there are several restrictions on secondary CRTC so
far since this is a quite new function.

* H/W overlay for MPEG2, DVD or any video playback can not be supported.
* DOS full screen mode can not be supported.

* Duplicate VRAM resource for LCD screen and CRT screen because of different
desktop size.

So still simultaneous display with single CRTC need to be supported for the
above applications.

  How single CRTC simultaneous display can be supported with SXGA+ panel for
1Q/2000 ThinkPad?

As it is mentioned above, in case of single CRTC, only one display timing can
be set for internal LCD and external CRT.

In case of internal SXGA+ LCD, CRTC should be set for it and it can not be
used for external CRT.

Since SXGA+ LCD has exactly same display timings as standard SXGA(1280x1024)
60Hz CRT's except for its display area, it can be displayed on CRT but some of
image area can not be seen correctly.(It will not be adjusted even if the
image position is shifted by CRT control)

In addition, since ThinkPad was annaunced, screen device swicth hot key
function(LCD->LCD+CRT->CRT) has been supported.

SXGA+ ThinkPad may not support this traditional function as well.

In order to overcome the issues, here is an idea.
1. To keep 1400x1050 full resolution, display 1400x1050 full desktop when LCD
only mode.
2. When LCD+CRT mode, to change desktop size to standard SXGA, 1280x1024 and
display 1400x1050 desktop as so called panning mode.

Panning mode: When desktop size is larger than physical display
resolution(area), some part of desktop are hidden...