CURRENT on Dell PE600SC panics on boot

All,

I've got one of the newer Dell PowerEdge 600SC servers with the 533MHz
planar board (I believe the P4 PE600SCs all have this board but the Celerons
have the 400MHz with a lower performance ATA setup) and I can't get -CURRENT
to boot on it. I get a kernel panic right before where the ATA drive
information would print. Right now I've got the basic config as shipped from
Dell with one 40GB IBM drive as master (CS) on the "primary" ATA channel,
nothing on the "secondary" ATA channel, and the CDROM drive on the
"tertiary" channel (per the Dell information update -- note that this is
different from the 400MHz planar boards). I can boot the generic kernel from
5.0-RELEASE just fine, but when I try and boot a generic kernel
from -CURRENT (I've tried several, cvsuping at various dates between 30-MAR
and 7-APR), I drop into the debugger here:

[...]
sc0: <System console> at flags 0x100 on isa0
sc0: VGA <16 virtual consoles, flags=0x300>
vga0: <Generic ISA VGA> at port 0x3c0-0x3df iomem 0xa0000-0xbffff on isa0
Timecounters tick every 10.000 msec

Fatal trap 12: page fault while in kernel mode
fault virtual address  = 0x20
fault code             = supervisor read, page not present
instruction pointer    = 0x8 :0xc01c5e05
stack pointer          = 0x10:0xc8655cc8
frame pointer          = 0x10:0xc8655ce0
code segment           = bsae 0x0 limit 0xfffff, type 0x1b
                       = DPL 0, pres 1, def32 1, gran 1
processor eflags       = interrupt enabled, resume, IOPL = 0
current process        = 24 (irq11: atapci0)
kernel: type 12 trap, code=0
Stopped at      ata_generic_intr+0x35:  testb   $0x1,0x20(%eax)

So far my efforts at troubleshooting have included disabling DMA via
loader.conf:

hw.ata.ata_dma="0"
hw.ata.atapi_dma="0"
hw.ata.ata_tags="0"

Here's my dmesg from a -RELEASE boot with a -CURRENT (7-APR) world:
Copyright (c) 1992-2003 The FreeBSD Project.
Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994
        The Regents of the University of California. All rights reserved.
FreeBSD 5.0-RELEASE #0: Thu Jan 16 22:16:53 GMT 2003
    root_at_hollin.btc.adaptec.com:/usr/obj/usr/src/sys/GENERIC
Preloaded elf kernel "/boot/kernel.old/kernel" at 0xc0672000.
Preloaded elf module "/boot/kernel/acpi.ko" at 0xc06720b8.
link_elf: symbol eventhandler_prune_list undefined
KLD file acpi.ko - could not finalize loading
Timecounter "i8254"  frequency 1193182 Hz
Timecounter "TSC"  frequency 2399335160 Hz
CPU: Pentium 4 (2399.34-MHz 686-class CPU)
  Origin = "GenuineIntel"  Id = 0xf27  Stepping = 7

Features=0xffffffffbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR
,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,<b31>>
real memory  = 134152192 (127 MB)
avail memory = 123404288 (117 MB)
Initializing GEOMetry subsystem
Pentium Pro MTRR support enabled
npx0: <math processor> on motherboard
npx0: INT 16 interface
Using $PIR table, 7 entries at 0xc00fc320
pcib0: <ServerWorks host to PCI bridge(unknown chipset)> at pcibus 0 on
motherboard
pci0: <PCI bus> on pcib0
em0: <Intel(R) PRO/1000 Network Connection, Version - 1.4.7> port
0xecc0-0xecff mem 0xfe100000-0xfe11ffff irq 10 at device 2.0 on pci0
em0:  Speed:100 Mbps  Duplex:Full
pci0: <display, VGA> at device 8.0 (no driver attached)
atapci0: <Generic PCI ATA controller> port
0x900-0x90f,0x36c-0x36f,0x168-0x16f,0x3ec-0x3ef,0x1e8-0x1ef irq 11 at device
14.0 on pci0
ata2: at 0x1e8 on atapci0
ata3: at 0x168 on atapci0
atapci1: <Generic PCI ATA controller> port
0x8b0-0x8bf,0x374-0x377,0x170-0x177,0x3f4-0x3f7,0x1f0-0x1f7 at device 15.1
on pci0
ata0: at 0x1f0 irq 14 on atapci1
ata1: at 0x170 irq 15 on atapci1
ohci0: <OHCI (generic) USB controller> mem 0xfe120000-0xfe120fff irq 5 at
device 15.2 on pci0
usb0: OHCI version 1.0, legacy support
usb0: SMM does not respond, resetting
usb0: <OHCI (generic) USB controller> on ohci0
usb0: USB revision 1.0
uhub0: (0x1166) OHCI root hub, class 9/0, rev 1.00/1.00, addr 1
uhub0: 2 ports with 2 removable, self powered
isab0: <PCI-ISA bridge> at device 15.3 on pci0
isa0: <ISA bus> on isab0
pcib255: <ServerWorks host to PCI bridge(unknown chipset)> at pcibus 255 on
motherboard
pci255: <PCI bus> on pcib255
orm0: <Option ROMs> at iomem 0xec000-0xeffff,0xc0000-0xc7fff on isa0
pmtimer0 on isa0
atkbdc0: <Keyboard controller (i8042)> at port 0x64,0x60 on isa0
atkbd0: <AT Keyboard> flags 0x1 irq 1 on atkbdc0
kbd0 at atkbd0
fdc0: <Enhanced floppy controller (i82077, NE72065 or clone)> at port
0x3f7,0x3f0-0x3f5 irq 6 drq 2 on isa0
fdc0: FIFO enabled, 8 bytes threshold
fd0: <1440-KB 3.5" drive> on fdc0 drive 0
ppc0: <Parallel port> at port 0x378-0x37f irq 7 on isa0
ppc0: Generic chipset (ECP/PS2/NIBBLE) in COMPATIBLE mode
ppc0: FIFO with 16/16/8 bytes threshold
plip0: <PLIP network interface> on ppbus0
lpt0: <Printer> on ppbus0
lpt0: Interrupt-driven port
ppi0: <Parallel I/O> on ppbus0
sc0: <System console> at flags 0x100 on isa0
sc0: VGA <16 virtual consoles, flags=0x300>
sio0 at port 0x3f8-0x3ff irq 4 flags 0x10 on isa0
sio0: type 16550A
vga0: <Generic ISA VGA> at port 0x3c0-0x3df iomem 0xa0000-0xbffff on isa0
unknown: <PNP0501> can't assign resources (port)
unknown: <PNP0401> can't assign resources (port)
unknown: <PNP0700> can't assign resources (port)
unknown: <PNP0303> can't assign resources (port)
unknown: <PNP0b00> can't assign resources (port)
unknown: <PNP0c01> can't assign resources (port)
Timecounters tick every 10.000 msec
ad0: 38146MB <IC35L040AVVA07-0> [77504/16/63] at ata0-master PIO4
acd0: CDROM <GCR-8481B> at ata2-master PIO4
Mounting root from ufs:/dev/ad0s2a

Can anyone give me any suggestions on what I might try to get this thing to
run CURRENT nicely? Any other output I can provide?

Josh