Category : Display Utilities
Archive   : UNIVBE43.ZIP
Filename : BUGS

Log of BUGS and problems with the Universal VESA VBE
----------------------------------------------------

This file documents known problems with the Universal VESA VBE. SciTech
Software have done their best to try to fix all know problems, but some
still persist and may well be limitations in the particular video controller
hardware and may not be fixable.

Trident 8900 chipsets:

- The Trident 8900 chipset does not seem to be able to page flip
the 1024x768 16 color video mode, even though it works for all
other video modes. Probably a bug in the chipset, since it does
seem to work on the newer 8900C video cards.

Tseng Labs ET3000AX chipsets:

- The 800x600x16 color mode seems to wrap the 256k boundary, and at
this stage there is now known solution.

Weitek 5186/5286 chipsets:

- For the moment the support seems to work, however there is a small
bug that causes the card to do strange things after a mode has been
set a number of times.

Chips & Technologies 82c45x chipsets:

- These chipsets seem to not be working at all at the moment, and the
problem is being looked into.

Compaq QVision chipsets:

- The Compaq QVision cards are detected however the support is
currently not working. This is currently being looked into.

S3 chipsets:

- The S3 86c911 has some severe bugs in the extended CRT addressing
code in 1024x768 16 color modes. Page flipping works but looks
disgusting (bottom 1/8th of the screen is trashed). This bug is
fixed in the 924 and later chipsets.

- Seems to be some bugs in the B-step 801/805 chipsets that cause the
UniVBE to do strange things. Works on all the ones that I have
tested.

Video7 chipsets:

- Extended CRT addressing does not seem to be enable correctly in the
standard VGA 16 and 256 color modes.

ATI Mach32:

- Even though the ATI Mach32 chipset can have a TrueColor DAC on board,
and can support HiColor and TrueColor modes, these modes are only
available to the accelerator. It is possible to initiliase these
modes for direct framebuffer access, however they do not behave as
normal VGA modes (the usual VGA CRT controller status registers
remain idle, hence code that waits for a vertical retrace will
simply hang in an infinite loop). Thus support for these modes
is not provided (even though the ATI VVESA.COM program attempts
to support these mode - it also causes many programs to hang for
the same reason).

320x200x256 standard VGA mode:

- Many SuperVGA chipsets seems to disable the bank switching registers
in the VGA standard 320x200x256 video mode, and hence extended page
flipping techniques do not work. This may be solveable for some
chipsets, or it may well be a hardware related problem (backwards
compatability with the standard VGA). The chipsets that are known to
currently suffer from this are:

Cirrus Logic 54xx
ATI
Video7
NCR
Oak

QEMM memory manager:

- QEMM does some wierd things with the video BIOS, so you may encounter
problems when using the Universal VESA VBE with QEMM installed.
You will need to use the exclude option to get it to work at all
(see the readme file).