Re: difference in maximum color depth in Debian vs Mac OS?

[Fernan Aguero <fernan@iib.unsam.edu.ar>]

+----[ Hans Ekbrand <hans@sociologi.cjb.net> (31.Jan.2005 14:53):
|
| > The VRAM of this Macintosh is 1MB (expandable to 4MB I
| > believe). However what I fail to understand is why the Mac
| > OS is able to get a higher color depth than debian/linux on
| > the same hardware.
| 
| I have similar problems, but I do have understanding of the issues at
| hand and I think I know why the following failed for you.

Hans,

thanks for the answer. 

 
| > debian:~# fbset -fb /dev/fb0 -depth 16 "832x624-75"
| 
| The problem is the speed of the graphic chip, not lack of RAM. I have
| a Macintosh Performa 5400 with the valkyrie graphic chip and if it the
| same as yours, MacOS cannot give 16 bpp at that mode, it only
| handles 16 bpp at 800x600@60HZ.

The graphic chip of the 7200 is the platinum, and my MacOS does give me 16 bpp
at 832x624@75Hz. This is the list of available resolutions and frequencies I
see in Mac OS: 

640x480@67Hz (256 grays, 256 colors, Thousands of Colors)
832x624@75Hz (256 grays, 256 colors, Thousands of Colors) 
1024x768@74.9Hz (256 grays, 256 colors)
1152x870@75Hz (256 grays, 256 colors)

This is with a Philips 107E5 monitor (17"), connected
through a NEC Multisync cable adapter.

| 
| :~# fbset -i
| 
| mode "800x600-60"
|     # D: 40.000 MHz, H: 37.879 kHz, V: 60.317 Hz
|     geometry 800 600 800 600 16
|     timings 25000 72 56 23 1 128 4
|     hsync high
|     vsync high
|     rgba 5/10,5/5,5/0,0/0
| endmode
| 
| Frame buffer device information:
|     Name        : valkyrie
|     Address     : 0xf1001000
|     Size        : 960000
|     Type        : PACKED PIXELS
|     Visual      : DIRECTCOLOR
|     XPanStep    : 0
|     YPanStep    : 0
|     YWrapStep   : 0
|     LineLength  : 1600
|     MMIO Address: 0xf130a000
|     MMIO Size   : 64
|     Accelerator : No

This is what I get from 'fbset -i'

mode "832x624-75"
    # D: 57.597 MHz, H: 49.997 kHz, V: 74.959 Hz
    geometry 832 624 832 624 8
    timings 17362 208 48 39 1 64 3
    rgba 8/0,8/0,8/0,0/0
endmode

Frame buffer device information:
    Name        : platinum
    Address     : 0xf1000090
    Size        : 1048576
    Type        : PACKED PIXELS
    Visual      : PSEUDOCOLOR
    XPanStep    : 0
    YPanStep    : 0
    YWrapStep   : 0
    LineLength  : 864
    MMIO Address: 0xf8000000
    MMIO Size   : 4096
    Accelerator : No

| 
| It *might* be possible to get 832x624@16bpp but at a lower refresh
| rate.
|
+----]

Mmm ... yes, but how do I get the correct values for a
different refresh rate so that I can put them between in
/etc/fbset.modes. AFAIK there was no other entry for
832x624. The alternatives to check color at 16 bpp are
640x480 or 800x600.

Thanks for your answer,

Fernan