I've managed to install Slackware with the default CD's and using the primary HD in the IT8212 card. I have an Asus P5GD2-Premium and the steps i've followed were:
Get the driver for the IT8212 at
www.ite.com.tw (the linux binaries and source) and
in another slack machine (with the default kernel)e us i'ved an approach i've read somewhere
1 - cd /usr/src/linux/drivers/scsi
2 - mv Makefile Makefile.original
3 - cp iteraid.* and cp Makefile (from the ITE source) into /usr/src/linux/drivers/scsi
4 - vi Makefile and changed the linux path to /usr/src/linux (line 2)
5 - run make (it gave me one warning but i got a file named iteraid.o
6 - cp that file into a vfat floppy
7 - Boot from the slack CD and run the default install lilo (bare.i)
8 - after boot and keyboard choosen i did a mount /dev/fd0 /mnt
9 - cd /mnt
10 - insmod iteraid.o (you can do a lsmod to see that the iteraid appears in the modules list)
11 - Then i did a cfdisk /dev/scd5 and i got access to the HD.
Please tell me if it worked for you. I can send you the iteraid.o file if you want (since i cannot attach it to the post)