I just plugged in a Promise UltraDMA/33 Controller into my Alpha PC164SX-533
system; connected are IBM 22GB and 37GB DeskStar drives on separate channels.

The system machine checks when probing (this was -current as of two weeks ago
with a patch to alloc the bus master registers if > 0x10000).

panic() at panic+0xe4
machine_check() at machine_check+0x1fc
interrupt() at interrupt+0x134
XentInt() at XentInt+0x1c
--- interrupt (from ipl 6) ---
cia_swiz_io_read_1() at cia_swiz_io_read_1+0x4c
wdcprobe() at wdcprobe+0x21c
wdcattach() at wdcattach+0x6c
pciide_mapchan() at pciide_mapchan+0x84
pdc202xx_chip_map() at pdc202xx_chip_map+0x4b8
pciide_attach() at pciide_attach+0xec
config_attach() at config_attach+0x434
config_found_sm() at config_found_sm+0x54
pci_probe_bus() at pci_probe_bus+0x2d0
pciattach() at pciattach+0x174
config_attach() at config_attach+0x434
config_found_sm() at config_found_sm+0x54
ciaattach() at ciaattach+0x1d4
config_attach() at config_attach+0x434
config_found_sm() at config_found_sm+0x54
mbattach() at mbattach+0x148
config_attach() at config_attach+0x434
config_rootfound() at config_rootfound+0x6c
cpu_configure() at cpu_configure+0x44
configure() at configure+0x4c
main() at main+0x3b4
locorestart() at locorestart+0x64
--- root of call graph ---

Here's the boot message including the machine check:

 >>>boot
(boot dqa0.0.0.108.0 -flags A)
block 0 of dqa0.0.0.108.0 is a valid boot block
reading 14 blocks from dqa0.0.0.108.0
bootstrap code read in
base = 1de000, image_start = 0, image_bytes = 1c00
initializing HWRPB at 2000
initializing page table at 1d0000
initializing machine state
setting affinity to the primary CPU
jumping to bootstrap code

NetBSD/alpha 1.4J FFS Primary Bootstrap
Jumping to entry point...

NetBSD/alpha 1.4J Secondary Bootstrap, Revision 1.10
(matt@center.home.3am-software.com, Aug 16 17:23:18 PDT 1999)

VMS PAL rev: 0x1000600010114
OSF PAL rev: 0x1000600020116
Switch to OSF PAL code succeeded.

Boot flags: A

Loading netbsd...
2193672+256016 [85+144384+78678]

Entering netbsd at 0xfffffc0000301170...
[ preserving 224048 bytes of netbsd ELF symbol table ]
Copyright (c) 1996, 1997, 1998, 1999
     The NetBSD Foundation, Inc.  All rights reserved.
Copyright (c) 1982, 1986, 1989, 1991, 1993
     The Regents of the University of California.  All rights reserved.

NetBSD 1.4K (CENTER2) #22: Tue Sep 21 14:20:41 PDT 1999
     matt@center.local:/other/src/sys/arch/alpha/compile/CENTER2
Digital AlphaPC 164SX 533 MHz
8192 byte page size, 1 processor.
total memory = 128 MB 
(1920 KB reserved for PROM, 126 MB used by NetBSD)
avail memory = 96984 KB
using 3228 buffers containing 25824 KB of memory
mainbus0 (root)
cpu0 at mainbus0: ID 0 (primary), PCA56-2 (unknown minor type 2)
cia0 at mainbus0: DECchip 2117x Core Logic Chipset (Pyxis), pass 1
cia0: extended capabilities: 1<BWEN>
cia0: using BWX for PCI config access
pci0 at cia0 bus 0
pci0: i/o enabled, memory enabled
fxp0 at pci0 dev 5 function 0: Intel i82557 Ethernet, rev 5
fxp0: interrupting at eb164 irq 9
fxp0: Ethernet address 00:a0:c9:ef:48:14, 10/100 Mb/s
inphy0 at fxp0 phy 1: i82555 10/100 media interface, rev. 0
inphy0: 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto
pciide0 at pci0 dev 6 function 0: Promise Ultra33/ATA Bus Master IDE Accelerator
pciide0: bus-master DMA support present
pciide0: primary channel configured to native-PCI mode
pciide0: using eb164 irq 11 for native-PCI interrupt

unexpected machine check:

     mces    = 0x1
     vector  = 0x660
     param   = 0xfffffc0000006068
     pc      = 0xfffffc000049666c
     ra      = 0xfffffc0000326c5c
     curproc = 0xfffffc000053d410
         pid = 0, comm = swapper

panic: machine check
Stopped in swapper at   Debugger+0x4:   ret     zero,(ra)
db> 
-- 
Matt Thomas               Internet:   matt@3am-software.com
3am Software Foundry      WWW URL:    http://www.3am-software.com/bio/matt/
Cupertino, CA             Disclaimer: I avow all knowledge of this message