NAME

Xqvss - X window system QVSS implementation notes

DESCRIPTION

The QVSS hardware in the DEC VS1 and VS2 is monochrome.  The usable size is 864 lines by 960 pixels/line.  (Future driver mods will default to 1024 pixels/line on the VR260 monitor of the VS2, in Ultrix 1.2; for VR260 monitors under 1.1, patch the kernel variable qv_def_scrn to 2.). 

Probably the most irritating problem with the QVSS hardware is the cursor support, which is limited to 16x16.  As only “and” and “or” operations are available in the hardware, the driver inverts the cursor depending upon the pixels below the cursor.  We will eventually get fed up and implement a software cursor. 

Under Ultrix-32 release 1.1 and 4.2BSD, the window system will be slightly unreliable due to a kernel problem.  Fixed in Ultrix32 release 1.2.  Under Ultrix-32 1.1, your best bet is to use unix domain connections (unix:0 as host spec’s) for local connections. 

Thanks must go to Dave Carver (and others) in the DEC Workstations group for implementing the bit-blit library.  Large area bit-blit code is compiled on the fly and runs at optimal speed. 

Performance is now tolerable, between 3400 and 4200 characters/second on a VS2.  Performance on a VS1 is approximately 2000 characters/second.  Some further improvement can be expected. 

SEE ALSO

X(8c), X(1)
‘Xlib - C Language X Interface’
‘ddX - Device Dependent X Interface’

AUTHOR

Copyright (c) 1984, 1985, 1986 by Massachusetts Institute of Technology. 
See X(1) for a complete Copyright notice.