diff --git a/Memory Management.md b/Memory Management.md
index dbc54bf..9f2d4e3 100644
--- a/Memory Management.md	
+++ b/Memory Management.md	
@@ -44,7 +44,7 @@ In the case of memory regions 2 and 6, if bits 4 and 5 of `PCS7` are both set, a
 
 ## Main RAM
 
-Sentinel 65X comes with 2MB of fast static RAM on the board. This memory is available in both 6502 emulation mode (in which only addresses from `0x0000` to `0xffff` are valid) and in 65816 native mode.
+Sentinel 65X comes with 2MB of fast static RAM on the board (512KB in the prototypes). This memory is available in both 6502 emulation mode (in which only addresses from `0x0000` to `0xffff` are valid) and in 65816 native mode.
 
 ## Main ROM