Redhat Advance Server 3.0(AMD)内存问题求助

zircal

我有一台AMD 2*Opteron 16G DDR的机器，运行中如果内存不够的时机器就会宕机，并提示North bridge error。这时系统就需要重新启动。
top的状态：
74 processes: 70 sleeping, 4 running, 0 zombie, 0 stopped
CPU states: cpu user nice system irq softirq iowait idle
total 77.0% 0.0% 0.4% 0.0% 0.0% 0.0% 22.5%
cpu00 54.1% 0.0% 0.8% 0.0% 0.0% 0.0% 45.0%
cpu01 100.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
Mem: 16211848k av, 12724428k used, 3487420k free, 0k shrd, 142672k buff
5171236k actv, 5669992k in_d, 199184k in_c
Swap: 17406416k av, 84k used, 17406332k free 8557892k cach
d

PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME CPU COMMAND
5867 richard 25 0 2510M 2.5G 15812 R 49.9 15.8 78:03 1 Astro
10019 richard 25 0 1102M 1.1G 13640 R 27.4 6.9 2:28 0 Astro
10024 root 15 0 1432 1432 1076 R 0.1 0.0 0:00 0 top
1 root 15 0 520 520 452 S 0.0 0.0 0:04 0 init
2 root RT 0 0 0 0 SW 0.0 0.0 0:00 0 migration/0
3 root RT 0 0 0 0 SW 0.0 0.0 0:00 1 migration/1
4 root 15 0 0 0 0 SW 0.0 0.0 0:00 0 keventd
5 root 34 19 0 0 0 SWN 0.0 0.0 0:00 0 ksoftirqd/0
6 root 34 19 0 0 0 SWN 0.0 0.0 0:00 1 ksoftirqd/1
9 root 25 0 0 0 0 SW 0.0 0.0 0:00 0 bdflush
7 root 15 0 0 0 0 SW 0.0 0.0 0:08 0 kswapd
8 root 15 0 0 0 0 SW 0.0 0.0 0:05 0 kscand
10 root 15 0 0 0 0 SW 0.0 0.0 0:01 0 kupdated
11 root 25 0 0 0 0 SW 0.0 0.0 0:00 0 mdrecoveryd

请问红色标记的in_d，in_c是什么意思。
对于死机的问题我怀疑是cache不能自动释放或者就是in_d不能释放，请那位能给个解决办法