My motherboard, ASRock 775Dual-VSTA, uses the VT8237A southbridge chip.
The chip is not recognized by the most recent 2.6.17 series kernels.
This is a fairly new board that supports the new Intel Core 2 Duo processors.
I think the VT8237A must be a minor variation on VIA's existing VT8237 chip
which *is* supported by the kernel.

This problem is rectified by applying a really simple patch to 2 files (files are attached).

Without the patch I get errors booting the stock arch kernel or the beyond kernel:

:: Loading initramfs
:: Running Hook [udev]
:: Loading udev...input: AT Translated Set 2 keyboard as /class/input/input0
Uniform Multi-Platform E-IDE driver revision: 7.00alpha2
ide: Assuming 33 Mhz system bus speed for PIO modes; override with idebus=xx
VP_IDE: Chipset revision 7
VP_IDE: not 100% native mode: will probe irqs later
VP_IDE: Unknown VIA southbridge, disabling DMA
done
:: Running Hook [filesystems[
:: Loading root filesystem module...reiserfs
:: Initramfs completed - control passing to kinit
kinit: Cannot open root device (0,0)
kinit: init not found!
kernel panic-not syncing Attempted to kill init.

Patching the kernel solves the problem. I tested the patch on the beyond kernel,
and I'm now able to boot with DMA enabled.

Oddly, I can boot a kernel compiled from kernel.org even when it is unpatched.
I still receive the following error and DMA is disabled, but the kernel boots:
VP_IDE: Unknown VIA southbridge, disabling DMA

I'm fairly certain that anyone else that happens to be installing Arch on
a motherboard with the same VT8237A southbridge will be unable to boot without the patch
until the kernel is updated.