Messages in this thread | | | Date | Mon, 31 May 1999 12:57:20 +0200 | From | Gabor Lenart <> | Subject | Re: vgacon & mdacon hercules related question |
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On Mon, May 31, 1999 at 12:12:26PM +0200, Martin Mares wrote: > The problem is that the video memory size detection routines in mdacon.c > are not 100% reliable. I've already seen several bug reports on this and it > seems we'll have to add a optional parameter to override the size. I want > vgacon (being the default console driver on PC's) to work perfectly with > all cards, even if it means scrollback being unsupported on the HGC.
As far as I know there would be two ways to detect hercules :
* Detecting with different video memory size (write a byte, read back, compare) * There is a bit on a hercules port which inditcated vertical (or horizontal) retrace. This technique is used in mdacon to detect hercules.
(A nice question : what are hercules plus and hercules color ? I haven't managed to seek any information on them ...)
> Anyway, we might try adding a command-line option for specifying the > size manually or just detect HGC and assume minimum memory size possible > for a HGC. This (and setting vga_hardscroll_enable to 1) should be enough > to get a working hardware scrolling and scrollback.
I hard-wired some settings on my Linux machine with only a hercules display (instead of auto detecting) :
display_desc="*HGC"; request_region(0x3b0,16,"hgc"); vga_vram_base=0xb0000; vga_vram_address=0xb8000; vga_hardscroll_enabled=1;
The result was strange ... On screen scrolling everything messed up :( Changing VT away and back fix the problem till the next scroll event. [Temporary I created a syscall to controll my kernel changes :) and without enabling hardscroll on HGC everything worked OK with my console changes too. So the problem is with hardscroll on hgc.]
However creating kernel parameter to force using HGC (with hardscroll) is a good idea, I think.
> > The best thing would be separated mda and vga console code but it has > > got one big disadvantage : kernel compiled to VGA console won't run > > on hercules and vice versa. I think there should be a cleaning about > > mda & vga console handling ... Also interesing things about dual heading > > system (VGA/Hercules). Maybe we should have only ONE driver for mda (and > > hercules too) / VGA with capability to handle multiple output (like VGA > > and MDA) ? > > Current situation is: > > o vgacon supports MDA, HGC, EGA and VGA cards, but can be > loaded only once. > o mdacon supports MDA/HGC as a secondary display, but it can be > also configured to take over the videocard and replace vgacon. > > It would be nice to have one driver which could be loaded multiple > times, but it isn't trivial to implement. > > > Another question : is there way to reduce the effect to sound playing of > > hercules displaying (for example using XF86_MONO ...) or this is the effect > > of the famous "excellent" PC architecture ? > > It's probably because of poor shielding of the sound card :-(
I don't think so because this is not that type of noise. Playing can be skipped for even seconds when scrolling display. Less agressive screen changing casues only strange noise. I heard that it is casued by the ISA arhitecture (it does not matter when I played with PCI/ISA pair of card instead of ISA/ISA ...)
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