小弟去INTEL挖了一下Datesheet
這是INTEL的說法
n Integrated DRAM controller
—8 to 512 Mbytes or 1 Gbyte (with registered DIMMs)
—Supports up to 4 double-sided DIMMs
(8 rows memory)
—64-bit data interface with ECC support
(SDRAM only)
—Unbuffered and Registered SDRAM (Synchronous)
DRAM
Support (x-1-1-1 access at 66 MHz, x-1-1-1
access at 100 MHz)
—Enhanced SDRAM Open Page Architecture Support
for 16- and 64-Mbit DRAM devices with 2-, 4- and 8-
Kbyte page sizes

小弟程度較差所以不確定ECC Reg SDRAM是不是就是INTEL提到的—Unbuffered and Registered SDRAM (Synchronous)

實際把四支256MB ECC REG SDRAM插到P3B-f使用的狀況是
每支都只抓到128MB，所以總合是512MB
（僅插單支時也只抓到128MB）

插滿四支256MB SDRAM OR插滿四支256MB ECC SDRAM都是正常的

或者這是ASUS的問題