I have an SS20 with twin SM71s and 512MB RAM.
I built an MP kernel (7.1_RC1). Following that and building a bunch of packages I see this error in dmesg:
NetBSD 7.1_RC1 (SYLVESTER) #0: Sun Feb 12 18:51:42 MST 2017
root@wilbur:/usr/obj/sys/arch/sparc/compile/SYLVESTER
total memory = 511 MB
avail memory = 496 MB
kern.module.path=/stand/sparc/7.1/modules
timecounter: Timecounters tick every 10.000 msec
bootpath: /iommu@f,e0000000/sbus@f,e0001000/espdma@f,400000/esp@f,800000/sd@1,0
mainbus0 (root): SUNW,SPARCstation-20: hostid 72c6d7b3
cpu0 at mainbus0: mid 8: TMS390Z50 v0 or TMS390Z55 @ 75 MHz, on-chip FPU
cpu0: physical 20K instruction (64 b/l), 16K data (32 b/l), 1024K external (32 b/l): cache enabled
cpu1 at mainbus0: mid 10: TMS390Z50 v0 or TMS390Z55 @ 75 MHz, on-chip FPU
cpu1: physical 20K instruction (64 b/l), 16K data (32 b/l), 1024K external (32 b/l): cache enabled
sx0 at mainbus0 ioaddr 0x80000000
sx0: architecture rev. 27 chip rev. 0
obio0 at mainbus0
clock0 at obio0 slot 0 offset 0x200000: mk48t08
timer0 at obio0 slot 0 offset 0x300000: delay constant 35, frequency = 2000000 Hz
timer: limit 0 shift 9 mask 3fffff
timecounter: Timecounter "timer-counter" frequency 2000000 Hz quality 100
zs0 at obio0 slot 0 offset 0x100000 level 12 softpri 6
zstty0 at zs0 channel 0 (console i/o)
zstty1 at zs0 channel 1
zs1 at obio0 slot 0 offset 0x0 level 12 softpri 6
zstty4 at zs1 channel 0
kbd0 at zstty4
zstty5 at zs1 channel 1
ms0 at zstty5
wsmouse0 at ms0 mux 0
fdc0 at obio0 slot 0 offset 0x700000 level 11: no drives attached
auxreg0 at obio0 slot 0 offset 0x800000
power0 at obio0 slot 0 offset 0xa01000 level 2
iommu0 at mainbus0 ioaddr 0xe0000000: version 0x3/0x1, page-size 4096, range 64MB
sbus0 at iommu0: clock = 25 MHz
dma0 at sbus0 slot 15 offset 0x400000: DMA rev 2
esp0 at dma0 slot 15 offset 0x800000 level 4: ESP200, 40MHz, SCSI ID 7
scsibus0 at esp0: 8 targets, 8 luns per target
ledma0 at sbus0 slot 15 offset 0x400010: DMA rev 2
le0 at ledma0 slot 15 offset 0xc00000 level 6: address 08:00:20:c6:d7:b3
le0: 8 receive buffers, 2 transmit buffers
bpp0 at sbus0 slot 15 offset 0x4800000 level 2 (ipl 3): DMA rev 2
dbri0 at sbus0 slot 14 offset 0x10000 level 9: rev e
cgsix0 at sbus0 slot 2 offset 0x0 level 9: SUNW,501-2325, 1152 x 900, rev 11
cgsix0: attached to /dev/fb0
cgsix0: framebuffer size: 1 MB
wsdisplay1 at cgsix0 kbdmux 1
wsmux1: connecting to wsdisplay1
eccmemctl0 at mainbus0 ioaddr 0x0: version 0x0/0x2
timecounter: Timecounter "clockinterrupt" frequency 100 Hz quality 0
cpu0: booting secondary processors: cpu1
scsibus0: waiting 2 seconds for devices to settle...
wskbd0 at kbd0 mux 1
sd0 at scsibus0 target 1 lun 0: <SEAGATE, ST32430W SUN2.1G, 0666> disk fixed
sd0: 2049 MB, 3992 cyl, 9 head, 116 sec, 512 bytes/sect x 4197405 sectors
sd0: sync (100.00ns offset 15), 8-bit (10.000MB/s) transfers, tagged queueing
sd1 at scsibus0 target 3 lun 0: <COMPAQ, BB018135B5, B013> disk fixed
sd1: 17365 MB, 7001 cyl, 20 head, 254 sec, 512 bytes/sect x 35565080 sectors
sd1: sync (100.00ns offset 15), 8-bit (10.000MB/s) transfers, tagged queueing
kbd0: reset failed
wskbd0: connecting to wsdisplay1
cd0 at scsibus0 target 6 lun 0: <TOSHIBA, XM-4101TASUNSLCD, 1084> cdrom removable
cd0: async, 8-bit transfers
Kernelized RAIDframe activated
dbri0: speakerbox detected
dbri0: cs4215 rev E found at offset 8
audio0 at dbri0: full duplex, playback, capture, mmap
root on sd0a dumps on sd0b
root file system type: ffs
cpu0: NMI: system interrupts: 0x10000000<VME=0x0,SBUS=0x0,M>
memory error:
EFSR: 0x8a31<CE,DW=0x3,SYNDROME=0x8a>
MBus transaction: 0x87ffcd50<VAH=0x0,TYPE=0x5,SIZE=0x5,C,VA=0xff,MID=0x8>
address: 0x01eb3ba80
module location: J0304
cpu0: NMI: system interrupts: 0x10000000<VME=0x0,SBUS=0x0,M>
memory error:
EFSR: 0x8a31<CE,DW=0x3,SYNDROME=0x8a>
MBus transaction: 0xa7ffcd50<VAH=0x0,TYPE=0x5,SIZE=0x5,C,VA=0xff,MID=0xa>
address: 0x01eb3ba80
module location: J0304
cpu0: NMI: system interrupts: 0x10000000<VME=0x0,SBUS=0x0,M>
memory error:
EFSR: 0x8a21<CE,DW=0x2,SYNDROME=0x8a>
MBus transaction: 0xa7ffcd50<VAH=0x0,TYPE=0x5,SIZE=0x5,C,VA=0xff,MID=0xa>
address: 0x01eb3ba8c
module location: J0304
I didn't see these errors while running a kernel build etc. with a single-cpu kernel (stock 7.0.1).