you seems to want ide-core.nodma= kernel option
check its usage, or maybe another more useful kernel options, here:
http://www.mjmwired.net/kernel/Documentation/kernel-parameters.txt
you can check or set dma settings with the command hdparm, e.g.

root@slitaz:/home/tux# hdparm /dev/hda

/dev/hda:
 multcount      = 16 (on)
 IO_support     =  1 (32-bit)
 unmaskirq      =  1 (on)
 using_dma      =  1 (on)
 keepsettings   =  0 (off)
 readonly       =  0 (off)
 readahead      = 256 (on)
 geometry       = 19929/255/63, sectors = 320173056, start = 0

if you run hdparm with no parameters you will see all options available.
you may want to check hdparm -d:

root@slitaz:/home/tux# hdparm -d /dev/hda

/dev/hda:
 using_dma      =  1 (on)
root@slitaz:/home/tux# hdparm -d0 /dev/hda

/dev/hda:
 setting using_dma to 0 (off)
 using_dma      =  0 (off)
root@slitaz:/home/tux# hdparm -d1 /dev/hda 

/dev/hda:
 setting using_dma to 1 (on)
 using_dma      =  1 (on)

Thanks for your reply! Yes, that seems what I need, just that now I'm confused, cause:

root@slitaz:/home/slete# hdparm /dev/hda

/dev/hda:
multcount = 16 (on)
IO_support = 0 (default 16-bit)
unmaskirq = 0 (off)
using_dma = 0 (off)
keepsettings = 0 (off)
readonly = 0 (off)
readahead = 256 (on)
geometry = 65535/16/63, sectors = 90069840, start = 0

It already says deactivated, strange, does it do a check on every boot up and then only deactivate it, if that fails?
How do I make those neat yellow boxes for code? (didn't find anything about that...)
Anyway, this is a part of the boot log, maybe somebody can figure out, what it exactly does with dma and why it's shown as off :

Uniform Multi-Platform E-IDE driver
via82cxxx 0000:00:04.1: VIA vt82c686a (rev 22) IDE UDMA66
via82cxxx 0000:00:04.1: IDE controller (0x1106:0x0571 rev 0x10)
via82cxxx 0000:00:04.1: not 100% native mode: will probe irqs later
ide0: BM-DMA at 0xb800-0xb807
ide1: BM-DMA at 0xb808-0xb80f
Probing IDE interface ide0...
hda: IBM-DTLA-307045, ATA DISK drive
hdb: Maxtor 6Y120L0, ATA DISK drive
hda: host max PIO5 wanted PIO255(auto-tune) selected PIO4
hda: host side 80-wire cable detection failed, limiting max speed to UDMA33
hda: UDMA/33 mode selected
hdb: host max PIO5 wanted PIO255(auto-tune) selected PIO4
hdb: host side 80-wire cable detection failed, limiting max speed to UDMA33
hdb: UDMA/33 mode selected
Probing IDE interface ide1...
hdd: LTN526, ATAPI CD/DVD-ROM drive
hdd: host max PIO5 wanted PIO255(auto-tune) selected PIO4
hdd: UDMA/33 mode selected
ide0 at 0x1f0-0x1f7,0x3f6 on irq 14
ide1 at 0x170-0x177,0x376 on irq 15
ide_generic: please use "probe_mask=0x3f" module parameter for probing all legacy ISA IDE ports
ide-gd driver 1.18
hda: max request size: 128KiB
hda: 90069840 sectors (46115 MB) w/1916KiB Cache, CHS=65535/16/63
hda: cache flushes not supported
hda:<4>hda: ide_dma_sff_timer_expiry: DMA status (0x61)
hda: DMA timeout error
hda: dma timeout error: status=0x58 { DriveReady SeekComplete DataRequest }
hda: possibly failed opcode: 0xc8
hda: DMA disabled
hdb: DMA disabled
ide0: reset: success
hda1 hda2 hda3
hdb: max request size: 128KiB
hdb: 240121728 sectors (122942 MB) w/2048KiB Cache, CHS=65535/16/63
hdb: cache flushes supported
hdb: hdb1 < hdb5 >

if it was my pc:
1) i would use 80 wire ide cable
2) i would rebuild the kernel enabling this:
http://cateee.net/lkddb/web-lkddb/PATA_VIA.html
this is disabled in 3.0 kernel

root@slitaz:/home/tux# zcat /proc/config.gz | grep VIA 
# CONFIG_MVIAC3_2 is not set
# CONFIG_MVIAC7 is not set
# CONFIG_VIA_FIR is not set
CONFIG_BLK_DEV_VIA82CXXX=y
CONFIG_SATA_VIA=y
# CONFIG_PATA_VIA is not set
CONFIG_VIA_RHINE=y
CONFIG_VIA_RHINE_MMIO=y
CONFIG_VIA_VELOCITY=m
CONFIG_HW_RANDOM_VIA=y
# CONFIG_I2C_VIA is not set
# CONFIG_I2C_VIAPRO is not set
# CONFIG_SENSORS_VIA686A is not set
CONFIG_AGP_VIA=m
CONFIG_DRM_VIA=m
# CONFIG_FB_VIA is not set
CONFIG_SND_HDA_CODEC_VIA=y
CONFIG_SND_VIA82XX=m
CONFIG_SND_VIA82XX_MODEM=m
root@slitaz:/home/tux# 

if you rebuild the kernel you may want to check this:
http://forum.slitaz.org/index.php/discussion/931/solved-compiling-kernnel-with-initramfs-enabled-causes-error
if you can live with no dma and just don't want the pause try booting with

ide-core.nodma=0.0 ide-core.nodma=0.1 

kernel options
< pre >dont put spaces inside tags to have yellow box < /pre >

Thank you so much for your help :-)
Unfortunately I don't have the time right now to play around with it longer, but as soon as I find some time I'll try to rebuild the kernel.