port-i386/46792: spdmem fails to find all slots

[Bernd Ernesti <pr201202%veego.de@localhost>]

>Number:         46792
>Category:       port-i386
>Synopsis:       spdmem fails to find all slots
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    port-i386-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Aug 11 21:10:06 +0000 2012
>Originator:     Bernd Ernesti
>Release:        NetBSD 6.0_BETA2
>Organization:
>Environment:
System: NetBSD 6.0_BETA2
Architecture: i386
Machine: i386
>Description:
        A kernel 5.99.7 from around 2009-03-07 found two DIMMs:

spdmem0 at iic0 addr 0x50
spdmem0: DDR2 SDRAM, data ECC, 1GB, 800MHz (PC2-6400)
spdmem0: 14 rows, 10 cols, 2 ranks, 4 banks/chip, 2.50ns cycle time
spdmem0: tAA-tRCD-tRP-tRAS: 5-5-5-16
spdmem0: voltage SSTL 1.8V, refresh time 7.8us (self-refreshing)
spdmem1 at iic0 addr 0x51
spdmem1: DDR2 SDRAM, data ECC, 1GB, 800MHz (PC2-6400)
spdmem1: 14 rows, 10 cols, 2 ranks, 4 banks/chip, 2.50ns cycle time
spdmem1: tAA-tRCD-tRP-tRAS: 5-5-5-16
spdmem1: voltage SSTL 1.8V, refresh time 7.8us (self-refreshing) 

        Something changed between 2009-03-07 (5.99.7) and 2009-04-05 (5.99.10)
        so from now on the kernel only finds just one DIMM.
        The spdmem0 at 0x50 will no longer be found.

        This is the output from NetBSD 6.0_BETA2:

piixpm0 at pci0 dev 20 function 0: ATI Technologies SB600/SB700/SB800 SMBus 
Controller (rev. 0x3a)
piixpm0: interrupting at SMI, polling
iic0 at piixpm0: I2C bus
spdmem0 at iic0 addr 0x51
spdmem0: DDR2 SDRAM, data ECC, 1GB, 800MHz (PC2-6400)
spdmem0: 14 rows, 10 cols, 2 ranks, 4 banks/chip, 2.50ns cycle time
spdmem0: tAA-tRCD-tRP-tRAS: 5-5-5-16
spdmem0: voltage SSTL 1.8V, refresh time 7.8us (self-refreshing)

        Btw, this issue it not BIOS related because I successfully booted a
        5.1_STABLE earlier this year which showed both DIMMs.

>How-To-Repeat:
        Add the following lines to your kernel config and boot that
        kernel on a Asus m3a78 board
         spdmem* at iic? addr 0x50
         spdmem* at iic? addr 0x51

>Fix: