Memory errors with 64MB RAM?

[Mike "Ford" Ditto]

Forwarding this here too in case anyone thinks this is AIC-7xxx related...

From:	ford at omnicron.com (Mike "Ford" Ditto)
To:	linux-kernel at vger.rutgers.edu
Subject: Memory errors with 64MB RAM?

I recently upgraded the RAM in a 166MHz Pentium system and the new
memory doesn't seem to work (I get filesystem corruption, kernel paging
errors, and random SIGSEGVs to various programs).

Obviously, the first suspect is that the new memory is defective or
incompatible.  But I thought I would take a long shot and ask here if
there is anything to watch out for when running Linux on a PC with 64MB
or more memory.

The old configuration was 24MB (two 8MB SIMMs and two 4MB SIMMs).  The
new configurations I tried were two 32MB SIMMs alone (64MB total) and
two 32MB plus two 8MB (80MB total).  The latter required giving a
mem=80M parameter when booting to get the whole 80MB recognized.  The
same failures happened with both 64MB and 80MB.  The new RAM is rated
appropriately for my motherboard (60ns EDO, same as the old RAM).

The reason I think there might be a software/configuration/driver
problem is the fact that the system actually ran well for a few days,
booting and running on an IDE disk, and then started acting up when I
started accessing a SCSI drive which hadn't previously been accessed
since adding the new RAM (aside from just being mounted).

The filesystem on the SCSI disk was corrupted, and when I ran fsck on
the SCSI disk with the new memory installed, fsck would just dump core
(SIGSEGV).  fsck would work fine on the IDE partitions, however.  When I
got rid of the new RAM, fsck was able to run to completion on the SCSI
filesystem.

So I make the wild speculation that there is some problem with DMA from
the PCI SCSI adapter when there is a lot of RAM in the system.

What do you think?  Is there something the prevents my system from
running Linux with 64MB of RAM, or is it a simple case of defective RAM?
I will ask the vendor to replace the new RAM and try again unless
someone thinks of something that could be wrong on the Linux side of
things.

			Thanks in advance...


The hardware:
cpu		: 586
model		: Pentium 75+
vendor_id	: GenuineIntel
stepping	: 12
PCI devices found:
  Bus  0, device  20, function  0:
    SCSI storage controller: Adaptec AIC-7881U (rev 0).
      Medium devsel.  Fast back-to-back capable.  IRQ 9.  Master Capable.  Latency=32.  Min Gnt=8.Max Lat=8.
      I/O at 0xfc00.
      Non-prefetchable 32 bit memory at 0xffbdf000.
  Bus  0, device  19, function  0:
    Ethernet controller: Realtek 8029 (rev 0).
      Medium devsel.  Fast back-to-back capable.  IRQ 9.  
      I/O at 0xff40.
  Bus  0, device  18, function  0:
    VGA compatible controller: ATI 210888GX (rev 1).
      Medium devsel.  IRQ 170.  
      Non-prefetchable 32 bit memory at 0xff000000.
  Bus  0, device   7, function  1:
    IDE interface: Intel 82371 Triton PIIX (rev 2).
      Medium devsel.  Fast back-to-back capable.  Master Capable.  Latency=32.
      I/O at 0x8000.
  Bus  0, device   7, function  0:
    ISA bridge: Intel 82371 Triton PIIX (rev 2).
      Medium devsel.  Fast back-to-back capable.  Master Capable.  No bursts.
  Bus  0, device   0, function  0:
    Host bridge: Intel 82437 (rev 2).
      Medium devsel.  Master Capable.  Latency=32.
Attached devices: 
Host: scsi0 Channel: 00 Id: 00 Lun: 00
  Vendor: SEAGATE  Model: ST15230W SUN4.2G Rev: 0738
  Type:   Direct-Access                    ANSI SCSI revision: 02

The software:
Linux version 2.0.33 (ford at han) (gcc version 2.7.2) #3 Wed Apr 8 15:38:20 PDT 1998
CONFIG_MODULES=y
CONFIG_KERNELD=y
CONFIG_NET=y
CONFIG_PCI=y
CONFIG_SYSVIPC=y
CONFIG_BINFMT_ELF=y
CONFIG_KERNEL_ELF=y
CONFIG_M586=y
CONFIG_BLK_DEV_FD=y
CONFIG_BLK_DEV_IDE=y
CONFIG_BLK_DEV_IDECD=y
CONFIG_BLK_DEV_TRITON=y
CONFIG_INET=y
CONFIG_IP_FORWARD=y
CONFIG_IP_MULTICAST=y
CONFIG_INET_RARP=y
CONFIG_IP_NOSR=y
CONFIG_SKB_LARGE=y
CONFIG_SCSI=y
CONFIG_BLK_DEV_SD=y
CONFIG_CHR_DEV_ST=m
CONFIG_BLK_DEV_SR=m
CONFIG_CHR_DEV_SG=m
CONFIG_SCSI_AIC7XXX=y
CONFIG_AIC7XXX_TAGGED_QUEUEING=y
CONFIG_AIC7XXX_PROC_STATS=y
CONFIG_AIC7XXX_RESET_DELAY=2
CONFIG_NETDEVICES=y
CONFIG_DUMMY=m
CONFIG_PPP=m
CONFIG_SLIP=m
CONFIG_SLIP_COMPRESSED=y
CONFIG_NET_ETHERNET=y
CONFIG_NET_ISA=y
CONFIG_NE2000=m
CONFIG_EXT2_FS=y
CONFIG_FAT_FS=m
CONFIG_MSDOS_FS=m
CONFIG_VFAT_FS=m
CONFIG_PROC_FS=y
CONFIG_NFS_FS=m
CONFIG_SMB_FS=m
CONFIG_ISO9660_FS=m
CONFIG_SERIAL=y
CONFIG_MOUSE=y
CONFIG_PSMOUSE=y
CONFIG_APM=y
CONFIG_APM_POWER_OFF=y
CONFIG_SOUND=y

					-=] Ford [=-

"God shuffled his feet			(In Real Life:  Mike Ditto)
 and glanced around at them. 		ford at omnicron.com
 The people cleared their throats	http://www.omnicron.com/~ford/ford.html
 and stared right back at him." - Crash Test Dummies

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