[SD/MMC] sd card write cache issue

my sd card's suddenly drops down when the block size >=1024KB
2013-6-4 19:33

i thought that may be the write cache feature has a limit of 512KB block size

anyone can help me?

computer : thinkpad x220
sd reader : ricoh pcie reader (x220 built-in)
card : toshiba exceria type 2 32GB