diff --git a/SD-Over-USB.md b/SD-Over-USB.md
index 963ba10..7fd2567 100644
--- a/SD-Over-USB.md
+++ b/SD-Over-USB.md
@@ -10,4 +10,6 @@ While the USB Mass Storage Mode is active, a little USB icon will be displayed.
 
 ![Screenshot 2023-04-01 193341](https://user-images.githubusercontent.com/13151053/229307649-d243f926-20a4-4f12-aa40-cfdbf010d1ba.jpg)
 
-Now just use the Portapack as if it was an sd card reader.
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+Now just use the Portapack as if it was an sd card reader.
+
+Note that "SD over USB" is very slow, around 400-500 kb/s, so in some cases it may be faster to remove the SD card and plug it into your computer.  It may take up to 2 hours to copy the 2GB world_map.bin file to the SD card using "SD over USB", for example.
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