I'm on x86, yes. I compiled the kernel using the manual from the official Arch Linux Wiki, I used the old config and just changed the 2 lines the manual told me to do.
I don't know anything about the framebuffer - when starting the sample_server without module radeonfb loaded he complains there's no /dev/fb0, after modprobe radeonfb it "works" and results in the output posted 2 mails ago (see below).
Running fbset -i results in this output:
[root@server tools]# fbset -i

mode "1280x1024-60"
    # D: 108.003 MHz, H: 63.983 kHz, V: 60.021 Hz
    geometry 1280 1024 1280 1024 8
    timings 9259 248 48 38 1 112 3
    hsync high
    vsync high
    rgba 8/0,8/0,8/0,0/0
endmode

Frame buffer device information:
    Name        : ATI Radeon NH
    Address     : 0xe8000000
    Size        : 134217728
    Type        : PACKED PIXELS
    Visual      : PSEUDOCOLOR
    XPanStep    : 8
    YPanStep    : 1
    YWrapStep   : 0
    LineLength  : 1280
    MMIO Address: 0xfe9f0000
    MMIO Size   : 16384
    Accelerator : Unknown (38)



[root@server miniglx]# ./sample_server && ./miniglx
[miniglx] probed chipset 0x4e48
got MMIOAddress 0xb7e45000 offset 134217728
shared virtual width is 1024
[drm] added 8192 byte SAREA at 0xf89cc000
[drm] mapped SAREA 0xf89cc000 to 0xb7e43000, size 8192
[drm] framebuffer handle = 0xe8000000
[drm] register handle = 0xfe9f0000
[gart] AGP enabled at 1x
[gart] 8192 kB allocated with handle 0x00000001
[gart] ring handle = 0xf8000000
[gart] ring read ptr handle = 0xf8101000
[gart] vertex/indirect buffers handle = 0xf8102000
[gart] AGP texture map handle = 0xf8302000
Using 8 MB AGP aperture
Using 1 MB for the ring buffer
Using 2 MB for vertex/indirect buffers
Using 1 MB for AGP textures
Will use back buffer at offset 0x400000
Will use depth buffer at offset 0x700000
Will use 120832 kb for textures at offset 0xa00000
[drm] Added 32 65536 byte vertex/indirect buffers
[drm] dma control initialized, using IRQ 16
[drm] Initialized kernel gart heap manager, 5111808
color tiling disabled
page flipping disabled
[miniglx] Setting mode: visible 1024x768 virtual 1024x768x32
[miniglx] Readback mode: visible 1024x768 virtual 1024x768x32
RADEONEngineRestore

On Mon, May 19, 2008 at 2:44 PM, Maurizio Rottin <maurizio.rottin@gmail.com> wrote:
2008/5/18, Simon Prückl <pruexxx@gmail.com>:
> I want to add that the screen is NOT only black as I told you a few hours
> ago, it's black and there's (barely visible in dark grey) the output of
> console.
> Changing to 16bit color depth results in a violet font.
>  In any case it's a total lock-up.

are you on x86 architecture, and compiled the kernel (and framebuffer)
by yourself?

--
mr



--
Simon Prückl - Prüxxx - Krift 43 - 4550 Kremsmünster