寒村のメモリを使ってるけど容量制限がない、謎

ベンチしたらクッソ速かったので貼っておく
DDR3-1333の4GBx2

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CrystalDiskMark 3.0.2 x64 (C) 2007-2012 hiyohiyo
Crystal Dew World : http://crystalmark.info/
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* MB/s = 1,000,000 byte/s [SATA/300 = 300,000,000 byte/s]

Sequential Read : 3960.512 MB/s
Sequential Write : 4894.516 MB/s
Random Read 512KB : 3678.754 MB/s
Random Write 512KB : 4475.948 MB/s
Random Read 4KB (QD=1) : 311.261 MB/s [ 75991.3 IOPS]
Random Write 4KB (QD=1) : 286.168 MB/s [ 69865.2 IOPS]
Random Read 4KB (QD=32) : 304.078 MB/s [ 74237.7 IOPS]
Random Write 4KB (QD=32) : 264.998 MB/s [ 64696.9 IOPS]

Test : 100 MB [Z: 0.7% (13.6/2046.0 MB)] (x5)
Date : 2012/11/22 8:16:02
OS : Windows 7 Home Premium Edition SP1 [6.1 Build 7601] (x64)