Getting rid of SDEXTRASLOW, SDSLOW variables.

Marlin/cardreader.cpp

   cardOK = false;
   if (root.isOpen()) root.close();
 
-  #if ENABLED(SDULTRASLOW)
-    #define SPI_SPEED SPI_SIXTEENTH_SPEED
-  #elif ENABLED(SDEXTRASLOW)
-    #define SPI_SPEED SPI_QUARTER_SPEED
-  #elif ENABLED(SDSLOW)
-    #define SPI_SPEED SPI_HALF_SPEED
-  #else
+  #ifndef SPI_SPEED
     #define SPI_SPEED SPI_FULL_SPEED
   #endif
 

Marlin/example_configurations/Felix/Configuration.h

 //#define DOGLCD  // Support for SPI LCD 128x64 (Controller ST7565R graphic Display Family)
 //#define SDSUPPORT // Enable SD Card Support in Hardware Console
 // Changed behaviour! If you need SDSUPPORT uncomment it!
-//#define SDSLOW // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDEXTRASLOW // Use even slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDULTRASLOW // Use slowest SD transfer mode (not normally needed - uncomment if you're getting volume init error)
+//#define SPI_SPEED SPI_HALF_SPEED // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
 //#define SD_CHECK_AND_RETRY // Use CRC checks and retries on the SD communication
 //#define ENCODER_PULSES_PER_STEP 1 // Increase if you have a high resolution encoder
 //#define ENCODER_STEPS_PER_MENU_ITEM 5 // Set according to ENCODER_PULSES_PER_STEP or your liking

Marlin/example_configurations/Felix/Configuration_DUAL.h

 //#define DOGLCD  // Support for SPI LCD 128x64 (Controller ST7565R graphic Display Family)
 //#define SDSUPPORT // Enable SD Card Support in Hardware Console
 // Changed behaviour! If you need SDSUPPORT uncomment it!
-//#define SDSLOW // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDEXTRASLOW // Use even slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDULTRASLOW // Use slowest SD transfer mode (not normally needed - uncomment if you're getting volume init error)
+//#define SPI_SPEED SPI_HALF_SPEED // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
 //#define SD_CHECK_AND_RETRY // Use CRC checks and retries on the SD communication
 //#define ENCODER_PULSES_PER_STEP 1 // Increase if you have a high resolution encoder
 //#define ENCODER_STEPS_PER_MENU_ITEM 5 // Set according to ENCODER_PULSES_PER_STEP or your liking

Marlin/example_configurations/Hephestos/Configuration.h

 #define ULTRA_LCD  //general LCD support, also 16x2
 //#define DOGLCD  // Support for SPI LCD 128x64 (Controller ST7565R graphic Display Family)
 #define SDSUPPORT // Enable SD Card Support in Hardware Console
-//#define SDSLOW // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDEXTRASLOW // Use even slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDULTRASLOW // Use slowest SD transfer mode (not normally needed - uncomment if you're getting volume init error)
+//#define SPI_SPEED SPI_HALF_SPEED // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
 //#define SD_CHECK_AND_RETRY // Use CRC checks and retries on the SD communication
 //#define ENCODER_PULSES_PER_STEP 1 // Increase if you have a high resolution encoder
 //#define ENCODER_STEPS_PER_MENU_ITEM 5 // Set according to ENCODER_PULSES_PER_STEP or your liking

Marlin/example_configurations/K8200/Configuration.h

 //#define DOGLCD  // Support for SPI LCD 128x64 (Controller ST7565R graphic Display Family)
 //#define SDSUPPORT // Enable SD Card Support in Hardware Console
 // Changed behaviour! If you need SDSUPPORT uncomment it!
-//#define SDSLOW // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDEXTRASLOW // Use even slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDULTRASLOW // Use slowest SD transfer mode (not normally needed - uncomment if you're getting volume init error)
+//#define SPI_SPEED SPI_HALF_SPEED // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
 //#define SD_CHECK_AND_RETRY // Use CRC checks and retries on the SD communication
 //#define ENCODER_PULSES_PER_STEP 1 // Increase if you have a high resolution encoder
 //#define ENCODER_STEPS_PER_MENU_ITEM 5 // Set according to ENCODER_PULSES_PER_STEP or your liking

Marlin/example_configurations/RepRapWorld/Megatronics/Configuration.h

 #define ULTRA_LCD  //general LCD support, also 16x2
 //#define DOGLCD  // Support for SPI LCD 128x64 (Controller ST7565R graphic Display Family)
 #define SDSUPPORT // Enable SD Card Support in Hardware Console
-//#define SDSLOW // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDEXTRASLOW // Use even slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDULTRASLOW // Use slowest SD transfer mode (not normally needed - uncomment if you're getting volume init error)
+//#define SPI_SPEED SPI_HALF_SPEED // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
 #define SD_CHECK_AND_RETRY // Use CRC checks and retries on the SD communication
 //#define ENCODER_PULSES_PER_STEP 1 // Increase if you have a high resolution encoder
 //#define ENCODER_STEPS_PER_MENU_ITEM 5 // Set according to ENCODER_PULSES_PER_STEP or your liking

Marlin/example_configurations/RigidBot/Configuration.h

 //#define DOGLCD  // Support for SPI LCD 128x64 (Controller ST7565R graphic Display Family)
 #define SDSUPPORT // Enable SD Card Support in Hardware Console
 // Changed behaviour! If you need SDSUPPORT uncomment it!
-//#define SDSLOW // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDEXTRASLOW // Use even slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-#define SDULTRASLOW // Use slowest SD transfer mode (not normally needed - uncomment if you're getting volume init error)
+#define SPI_SPEED SPI_EIGHTH_SPEED // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
 //#define SD_CHECK_AND_RETRY // Use CRC checks and retries on the SD communication
 //#define ENCODER_PULSES_PER_STEP 1 // Increase if you have a high resolution encoder
 //#define ENCODER_STEPS_PER_MENU_ITEM 5 // Set according to ENCODER_PULSES_PER_STEP or your liking

Marlin/example_configurations/SCARA/Configuration.h

 //#define DOGLCD  // Support for SPI LCD 128x64 (Controller ST7565R graphic Display Family)
 //#define SDSUPPORT // Enable SD Card Support in Hardware Console
 // Changed behaviour! If you need SDSUPPORT uncomment it!
-//#define SDSLOW // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDEXTRASLOW // Use even slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDULTRASLOW // Use slowest SD transfer mode (not normally needed - uncomment if you're getting volume init error)
+//#define SPI_SPEED SPI_HALF_SPEED // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
 //#define SD_CHECK_AND_RETRY // Use CRC checks and retries on the SD communication
 //#define ENCODER_PULSES_PER_STEP 1 // Increase if you have a high resolution encoder
 //#define ENCODER_STEPS_PER_MENU_ITEM 5 // Set according to ENCODER_PULSES_PER_STEP or your liking

Marlin/example_configurations/TAZ4/Configuration.h

 //#define DOGLCD  // Support for SPI LCD 128x64 (Controller ST7565R graphic Display Family)
 //#define SDSUPPORT // Enable SD Card Support in Hardware Console
 // Changed behaviour! If you need SDSUPPORT uncomment it!
-//#define SDSLOW // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDEXTRASLOW // Use even slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDULTRASLOW // Use slowest SD transfer mode (not normally needed - uncomment if you're getting volume init error)
+//#define SPI_SPEED SPI_HALF_SPEED // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
 //#define SD_CHECK_AND_RETRY // Use CRC checks and retries on the SD communication
 #define ENCODER_PULSES_PER_STEP 2 // Increase if you have a high resolution encoder
 #define ENCODER_STEPS_PER_MENU_ITEM 1 // Set according to ENCODER_PULSES_PER_STEP or your liking

Marlin/example_configurations/WITBOX/Configuration.h

 #define ULTRA_LCD  //general LCD support, also 16x2
 //#define DOGLCD  // Support for SPI LCD 128x64 (Controller ST7565R graphic Display Family)
 #define SDSUPPORT // Enable SD Card Support in Hardware Console
-//#define SDSLOW // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDEXTRASLOW // Use even slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDULTRASLOW // Use slowest SD transfer mode (not normally needed - uncomment if you're getting volume init error)
+//#define SPI_SPEED SPI_HALF_SPEED // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
 //#define SD_CHECK_AND_RETRY // Use CRC checks and retries on the SD communication
 //#define ENCODER_PULSES_PER_STEP 1 // Increase if you have a high resolution encoder
 //#define ENCODER_STEPS_PER_MENU_ITEM 5 // Set according to ENCODER_PULSES_PER_STEP or your liking

Marlin/example_configurations/adafruit/ST7565/Configuration.h

 //#define ULTRA_LCD  //general LCD support, also 16x2
 //#define DOGLCD  // Support for SPI LCD 128x64 (Controller ST7565R graphic Display Family)
 #define SDSUPPORT // Enable SD Card Support in Hardware Console
-#define SDSLOW // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDEXTRASLOW // Use even slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDULTRASLOW // Use slowest SD transfer mode (not normally needed - uncomment if you're getting volume init error)
+#define SPI_SPEED SPI_HALF_SPEED // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
 //#define SD_CHECK_AND_RETRY // Use CRC checks and retries on the SD communication
 //#define ENCODER_PULSES_PER_STEP 1 // Increase if you have a high resolution encoder
 //#define ENCODER_STEPS_PER_MENU_ITEM 5 // Set according to ENCODER_PULSES_PER_STEP or your liking

Marlin/example_configurations/delta/biv2.5/Configuration.h

 //#define DOGLCD  // Support for SPI LCD 128x64 (Controller ST7565R graphic Display Family)
 //#define SDSUPPORT // Enable SD Card Support in Hardware Console
 // Changed behaviour! If you need SDSUPPORT uncomment it!
-//#define SDSLOW // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDEXTRASLOW // Use even slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDULTRASLOW // Use slowest SD transfer mode (not normally needed - uncomment if you're getting volume init error)
+//#define SPI_SPEED SPI_HALF_SPEED // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
 //#define SD_CHECK_AND_RETRY // Use CRC checks and retries on the SD communication
 //#define ENCODER_PULSES_PER_STEP 1 // Increase if you have a high resolution encoder
 //#define ENCODER_STEPS_PER_MENU_ITEM 5 // Set according to ENCODER_PULSES_PER_STEP or your liking

Marlin/example_configurations/delta/generic/Configuration.h

 //#define DOGLCD  // Support for SPI LCD 128x64 (Controller ST7565R graphic Display Family)
 //#define SDSUPPORT // Enable SD Card Support in Hardware Console
 // Changed behaviour! If you need SDSUPPORT uncomment it!
-//#define SDSLOW // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDEXTRASLOW // Use even slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDULTRASLOW // Use slowest SD transfer mode (not normally needed - uncomment if you're getting volume init error)
+//#define SPI_SPEED SPI_HALF_SPEED // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
 //#define SD_CHECK_AND_RETRY // Use CRC checks and retries on the SD communication
 //#define ENCODER_PULSES_PER_STEP 1 // Increase if you have a high resolution encoder
 //#define ENCODER_STEPS_PER_MENU_ITEM 5 // Set according to ENCODER_PULSES_PER_STEP or your liking

Marlin/example_configurations/delta/kossel_mini/Configuration.h

 //#define DOGLCD  // Support for SPI LCD 128x64 (Controller ST7565R graphic Display Family)
 //#define SDSUPPORT // Enable SD Card Support in Hardware Console
 // Changed behaviour! If you need SDSUPPORT uncomment it!
-//#define SDSLOW // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDEXTRASLOW // Use even slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDULTRASLOW // Use slowest SD transfer mode (not normally needed - uncomment if you're getting volume init error)
+//#define SPI_SPEED SPI_HALF_SPEED // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
 //#define SD_CHECK_AND_RETRY // Use CRC checks and retries on the SD communication
 //#define ENCODER_PULSES_PER_STEP 1 // Increase if you have a high resolution encoder
 //#define ENCODER_STEPS_PER_MENU_ITEM 5 // Set according to ENCODER_PULSES_PER_STEP or your liking

Marlin/example_configurations/delta/kossel_pro/Configuration.h

 //#define ULTRA_LCD  //general LCD support, also 16x2
 //#define DOGLCD  // Support for SPI LCD 128x64 (Controller ST7565R graphic Display Family)
 #define SDSUPPORT // Enable SD Card Support in Hardware Console
-//#define SDSLOW // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDEXTRASLOW // Use even slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDULTRASLOW // Use slowest SD transfer mode (not normally needed - uncomment if you're getting volume init error)
+//#define SPI_SPEED SPI_HALF_SPEED // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
 //#define SD_CHECK_AND_RETRY // Use CRC checks and retries on the SD communication
 //#define ENCODER_PULSES_PER_STEP 1 // Increase if you have a high resolution encoder
 //#define ENCODER_STEPS_PER_MENU_ITEM 5 // Set according to ENCODER_PULSES_PER_STEP or your liking

Marlin/example_configurations/makibox/Configuration.h

 //#define ULTRA_LCD  //general LCD support, also 16x2
 //#define DOGLCD  // Support for SPI LCD 128x64 (Controller ST7565R graphic Display Family)
 #define SDSUPPORT // Enable SD Card Support in Hardware Console
-#define SDSLOW // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDEXTRASLOW // Use even slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDULTRASLOW // Use slowest SD transfer mode (not normally needed - uncomment if you're getting volume init error)
+#define SPI_SPEED SPI_HALF_SPEED // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
 //#define SD_CHECK_AND_RETRY // Use CRC checks and retries on the SD communication
 //#define ENCODER_PULSES_PER_STEP 1 // Increase if you have a high resolution encoder
 //#define ENCODER_STEPS_PER_MENU_ITEM 5 // Set according to ENCODER_PULSES_PER_STEP or your liking

Marlin/example_configurations/tvrrug/Round2/Configuration.h

 //#define DOGLCD  // Support for SPI LCD 128x64 (Controller ST7565R graphic Display Family)
 //#define SDSUPPORT // Enable SD Card Support in Hardware Console
 // Changed behaviour! If you need SDSUPPORT uncomment it!
-//#define SDSLOW // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDEXTRASLOW // Use even slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
-//#define SDULTRASLOW // Use slowest SD transfer mode (not normally needed - uncomment if you're getting volume init error)
+//#define SPI_SPEED SPI_HALF_SPEED // Use slower SD transfer mode (not normally needed - uncomment if you're getting volume init error)
 //#define SD_CHECK_AND_RETRY // Use CRC checks and retries on the SD communication
 //#define ENCODER_PULSES_PER_STEP 1 // Increase if you have a high resolution encoder
 //#define ENCODER_STEPS_PER_MENU_ITEM 5 // Set according to ENCODER_PULSES_PER_STEP or your liking