just a ping on PR 25829:
http://www.netbsd.org/cgi-bin/query-pr-single.pl?number=25829

I had this problem with NetBSD-2-0 on my alpha 1000A, and recently
updated to -current.

the workaround is to compile a custom kernel, but given that michael
hitch's patches look straightforward, I'm surprised they haven't been
committed yet.

the relevant pieces:

NetBSD 4.99.7 (GENERIC) #0: Sat Dec 30 06:27:08 PST 2006
	agrier@arwen.poofy.goof.com:/usr/obj/amd/aragorn/usr/projects/NetBSD/src/sys/arch/alpha/compile/GENERIC
AlphaServer 1000A 5/400, 400MHz, s/n 
8192 byte page size, 1 processor.
total memory = 256 MB
(2016 KB reserved for PROM, 254 MB used by NetBSD)
avail memory = 241 MB
mainbus0 (root)
cpu0 at mainbus0: ID 0 (primary), 21164A-2
cpu0: Architecture extensions: 1<BWX>
cia0 at mainbus0: DECchip 2117x Core Logic Chipset (ALCOR/ALCOR2), pass 3
cia0: extended capabilities: 21<DWEN,BWEN>
cia0: using BWX for PCI config access
pci0 at cia0 bus 0
pci0: i/o space, memory space enabled, rd/line, rd/mult, wr/inv ok
[...]
mlx0 at pci0 dev 12 function 0: Mylex RAID (v2 interface)
mlx0: interrupting at dec_1000a irq 3
mlx0: DAC960P/PD, 3 channels, firmware 2.70-0-00, 32MB RAM
ld0 at mlx0 unit 0: RAID5, online
ld0: 16380 MB, 8320 cyl, 64 head, 63 sec, 512 bytes/sect x 33546240 sectors
ld1 at mlx0 unit 1: RAID5, online
ld1: 32768 MB, 8322 cyl, 128 head, 63 sec, 512 bytes/sect x 67108864 sectors
ld2 at mlx0 unit 2: RAID5, online
ld2: 32768 MB, 8322 cyl, 128 head, 63 sec, 512 bytes/sect x 67108864 sectors
ld3 at mlx0 unit 3: RAID5, online
ld3: 4536 MB, 2304 cyl, 64 head, 63 sec, 512 bytes/sect x 9289728 sectors
[...]
WARNING: can't figure what device matches "RAID 0 12 0 0 0 0 0"
root device: ld0a
dump device (default ld0b): sd0b
[ yes, this is correct.  I have no ld0b. ]
file system (default generic): 
root on ld0a dumps on sd0b
root file system type: ffs
init path (default /sbin/init): 
init: trying /sbin/init

-- 
  Aaron J. Grier | "Not your ordinary poofy goof." | agrier@poofygoof.com
              "silly brewer, saaz are for pils!"  --  virt