Registry entries that seem to indicate that the Mio C320 supports SDIO:

[HKEY_LOCAL_MACHINE\Drivers]
"RootKey"="Drivers\\BuiltIn"

[HKEY_LOCAL_MACHINE\Drivers\Active]

[HKEY_LOCAL_MACHINE\Drivers\Active\30]
"Hnd"=dword:005405f0
"Name"="DSK2:"
"Key"="\\Drivers\\SDCARD\\ClientDrivers\\Class\\SDMemory_Class"
"BusParent"=dword:00047950
"InterfaceType"=dword:00000000
"BusName"="SDCARD_0_0_0"
"ClientInfo"=dword:0053e9d0

[HKEY_LOCAL_MACHINE\Drivers\Active\17]
"Hnd"=dword:00049e80
"Name"="SDH1:"
"Key"="Drivers\\BuiltIn\\SDHC_SMDK2443"
"BusParent"=dword:00030f60
"InterfaceType"=dword:00000000
"BusName"="BuiltInPhase1_0_14_0"

[HKEY_LOCAL_MACHINE\Drivers\Active\16]
"Hnd"=dword:00047950
"Name"="SDC1:"
"Key"="Drivers\\BuiltIn\\SDBusDriver"
"BusParent"=dword:00030f60
"InterfaceType"=dword:00000000
"BusName"="BuiltInPhase1_0_5_0"




[HKEY_LOCAL_MACHINE\Drivers\BuiltIn\SDBusDriver]
"Order"=dword:00000015
"Dll"="SDBus.dll"
"Prefix"="SDC"
"ThreadPriority"=dword:00000064
"RequestListDepth"=dword:00000030
"IClass"=hex(7):\
  7b,00,32,00,30,00,46,00,41,00,39,00,38,00,41,00,38,00,2d,00,42,00,32,00,39,\
  00,38,00,2d,00,34,00,62,00,33,00,32,00,2d,00,38,00,44,00,37,00,32,00,2d,00,\
  43,00,37,00,31,00,36,00,41,00,45,00,45,00,32,00,46,00,41,00,38,00,34,00,7d,\
  00,3d,00,25,00,62,00,00,00,7b,00,36,00,46,00,34,00,30,00,37,00,39,00,31,00,\
  44,00,2d,00,33,00,30,00,30,00,45,00,2d,00,34,00,34,00,45,00,34,00,2d,00,42,\
  00,43,00,33,00,38,00,2d,00,45,00,30,00,45,00,36,00,33,00,43,00,41,00,38,00,\
  33,00,37,00,35,00,43,00,7d,00,3d,00,25,00,62,00,00,00,00,00

[HKEY_LOCAL_MACHINE\Drivers\BuiltIn\SDHC_SMDK2443]
"Order"=dword:00000021
"Dll"="sdhc_sc2443.dll"
"Prefix"="SDH"
"DMAChannel"=dword:00000000
"DMAIrq"=dword:00000035
"DMA_IST_Priority"=dword:00000096
"SDIOIrq"=dword:00000015
"SDDetectIrq"=dword:00000020
"SDIO_IST_Priority"=dword:00000097
"PollingTimeout"=dword:00000100
"CardDetect_Thread_Priority"=dword:00000098
"CardDetectGPIO"="F"
"CardDetectMask"=dword:00000010
"CardDetectFlag"=dword:00000000
"CardDetectControlMask"=dword:fffffcff
"CardDetectControlFlag"=dword:00000000
"CardDetectPullupMask"=dword:fffffcff
"CardDetectPullupFlag"=dword:00000100
"CardReadWriteGPIO"="B"
"CardReadWriteMask"=dword:00000400
"CardReadWriteFlag"=dword:00000400
"CardReadWriteControlMask"=dword:ffcfffff
"CardReadWriteControlFlag"=dword:00000000
"CardReadWritePullupMask"=dword:ffcfffff
"CardReadWritePullupFlag"=dword:00100000
"HandleBusyFinishOnCommand38"=dword:00000001
"DmaTransferTimeoutFactor"=dword:00000008
"DmaTransferTimeoutConstant"=dword:00003000


[HKEY_LOCAL_MACHINE\Drivers\BuiltIn\PCI\Template\SDIOStandardHC]
"Dll"="SDHC.dll"
"Prefix"="SHC"
"IsrDll"="giisr.dll"
"IsrHandler"="ISRHandler"
"Class"=dword:00000008
"SubClass"=dword:00000005
"ProgIf"=dword:00000000
"DefaultWakeupSources"=dword:00000006
"AllowWakeOnSDIOInterrupts"=dword:00000001
"ObjectCreationProc"="CreateSDHCPciObject"

[HKEY_LOCAL_MACHINE\Drivers\BuiltIn\PCI\Template\SDIOStandardHCWithDMA]
"Dll"="SDHC.dll"
"Prefix"="SHC"
"IsrDll"="giisr.dll"
"IsrHandler"="ISRHandler"
"Class"=dword:00000008
"SubClass"=dword:00000005
"ProgIf"=dword:00000001
"DefaultWakeupSources"=dword:00000006
"AllowWakeOnSDIOInterrupts"=dword:00000001
"ObjectCreationProc"="CreateSDHCPciObject"


[HKEY_LOCAL_MACHINE\Drivers\SDCARD]

[HKEY_LOCAL_MACHINE\Drivers\SDCARD\ClientDrivers]

[HKEY_LOCAL_MACHINE\Drivers\SDCARD\ClientDrivers\Class]

[HKEY_LOCAL_MACHINE\Drivers\SDCARD\ClientDrivers\Class\SDMemory_Class]
"Dll"="SDMemory.dll"
"Prefix"="DSK"
"BlockTransferSize"=dword:00000040
"Profile"="SDMemory"
"IClass"=hex(7):\
  7b,00,41,00,34,00,45,00,37,00,45,00,44,00,44,00,41,00,2d,00,45,00,35,00,37,\
  00,35,00,2d,00,34,00,32,00,35,00,32,00,2d,00,39,00,44,00,36,00,42,00,2d,00,\
  34,00,31,00,39,00,35,00,44,00,34,00,38,00,42,00,42,00,38,00,36,00,35,00,7d,\
  00,00,00,7b,00,41,00,33,00,32,00,39,00,34,00,32,00,42,00,37,00,2d,00,39,00,\
  32,00,30,00,43,00,2d,00,34,00,38,00,36,00,62,00,2d,00,42,00,30,00,45,00,36,\
  00,2d,00,39,00,32,00,41,00,37,00,30,00,32,00,41,00,39,00,39,00,42,00,33,00,\
  35,00,7d,00,00,00,00,00

[HKEY_LOCAL_MACHINE\Drivers\SDCARD\ClientDrivers\Class\MMC_Class]
"Dll"="SDMemory.dll"
"Prefix"="DSK"
"BlockTransferSize"=dword:00000040
"Profile"="MMC"
"IClass"=hex(7):\
  7b,00,41,00,34,00,45,00,37,00,45,00,44,00,44,00,41,00,2d,00,45,00,35,00,37,\
  00,35,00,2d,00,34,00,32,00,35,00,32,00,2d,00,39,00,44,00,36,00,42,00,2d,00,\
  34,00,31,00,39,00,35,00,44,00,34,00,38,00,42,00,42,00,38,00,36,00,35,00,7d,\
  00,00,00,7b,00,41,00,33,00,32,00,39,00,34,00,32,00,42,00,37,00,2d,00,39,00,\
  32,00,30,00,43,00,2d,00,34,00,38,00,36,00,62,00,2d,00,42,00,30,00,45,00,36,\
  00,2d,00,39,00,32,00,41,00,37,00,30,00,32,00,41,00,39,00,39,00,42,00,33,00,\
  35,00,7d,00,00,00,00,00

[HKEY_LOCAL_MACHINE\Drivers\SDCARD\ClientDrivers\Class\SDIO_Class]

[HKEY_LOCAL_MACHINE\Drivers\SDCARD\ClientDrivers\Class\SDIO_Class\2]
"DLL"="bthsdio.dll"
"Prefix"="BSD"
"WakeOnSDIOInterrupts"=dword:00000001
"IClass"=hex(7):\
  7b,00,45,00,44,00,35,00,42,00,44,00,46,00,45,00,43,00,2d,00,33,00,42,00,44,\
  00,39,00,2d,00,34,00,63,00,63,00,37,00,2d,00,42,00,45,00,30,00,33,00,2d,00,\
  35,00,45,00,39,00,45,00,33,00,42,00,32,00,35,00,30,00,43,00,36,00,39,00,7d,\
  00,00,00,7b,00,41,00,33,00,32,00,39,00,34,00,32,00,42,00,37,00,2d,00,39,00,\
  32,00,30,00,43,00,2d,00,34,00,38,00,36,00,62,00,2d,00,42,00,30,00,45,00,36,\
  00,2d,00,39,00,32,00,41,00,37,00,30,00,32,00,41,00,39,00,39,00,42,00,33,00,\
  35,00,7d,00,00,00,00,00

[HKEY_LOCAL_MACHINE\Drivers\SDCARD\ClientDrivers\Class\SDIO_Class\3]
"DLL"="bthsdio.dll"
"Prefix"="BSD"
"WakeOnSDIOInterrupts"=dword:00000001
"IClass"=hex(7):\
  7b,00,45,00,44,00,35,00,42,00,44,00,46,00,45,00,43,00,2d,00,33,00,42,00,44,\
  00,39,00,2d,00,34,00,63,00,63,00,37,00,2d,00,42,00,45,00,30,00,33,00,2d,00,\
  35,00,45,00,39,00,45,00,33,00,42,00,32,00,35,00,30,00,43,00,36,00,39,00,7d,\
  00,00,00,7b,00,41,00,33,00,32,00,39,00,34,00,32,00,42,00,37,00,2d,00,39,00,\
  32,00,30,00,43,00,2d,00,34,00,38,00,36,00,62,00,2d,00,42,00,30,00,45,00,36,\
  00,2d,00,39,00,32,00,41,00,37,00,30,00,32,00,41,00,39,00,39,00,42,00,33,00,\
  35,00,7d,00,00,00,00,00