我用的是联想Y450，由于我要加内存，所以我要查查是几代内存，我拆机是PC3，也就是3代内存，但是用命令dmidecode -t memory查却是2代，是怎么回事，难道降级了？
# dmidecode 3.3
Getting SMBIOS data from sysfs.
SMBIOS 2.5 present.
Handle 0x000E, DMI type 16, 15 bytes
Physical Memory Array
Location: System Board Or Motherboard
Use: System Memory
Error Correction Type: None
Maximum Capacity: 4 GB
Error Information Handle: Not Provided
Number Of Devices: 2
Handle 0x000F, DMI type 17, 27 bytes
Memory Device
Array Handle: 0x000E
Error Information Handle: 0xFF3E
Total Width: 64 bits
Data Width: 64 bits
Size: 2 GB
Form Factor: DIMM
Set: 1
Locator: DIMM 1
Bank Locator: Bank 0, 1
Type: DDR2
Type Detail: Synchronous
Speed: 400 MT/s
Manufacturer: Not Specified
Serial Number: 00000000
Asset Tag: Not Specified
Part Number: Not Specified