update eeprom shadow info

git-svn-id: http://lm-sensors.org/svn/lm-sensors/trunk@2447 7894878c-1315-0410-8ee3-d5d059ff63e0

doc/FAQ

@@ -1044,10 +1044,11 @@ wanted.
 --------------------------------------------
 
    These are often 'shadows' of your EEPROMs on your SDRAM DIMMs at
-addresses 0x50 - 0x57. They aren't really there. If you try and do a
-`i2cdump' on them you won't get anything. This is probably caused by
-some timing problem on your motherboard or on the DIMMs.  We don't know
-the exact cause.
+addresses 0x50 - 0x57. They are the 'software write-protect' registers
+of the SDRAM Serial Presence Detect EEPROMs.  If you try and do a
+`i2cdump' on them to read the location, you won't get anything, because
+they contain a single write-only register.  This register can be used
+to permanently write-protect the contents of the eeprom.
 
 4.24 Sensors-detect doesn't work at all
 =======================================

doc/lm_sensors-FAQ.texi

@@ -1048,10 +1048,13 @@ look at some basic data in @command{sensors} or use the program
 @subsection What is at I2C addresses 0x30 - 0x37?
 
 These are often 'shadows' of your EEPROMs on your SDRAM DIMMs
-at addresses 0x50 - 0x57. They aren't really there. If you try and
-do a @command{i2cdump} on them you won't get anything. This is probably
-caused by some timing problem on your motherboard or on the DIMMs.
-We don't know the exact cause.
+at addresses 0x50 - 0x57. They are the 'software write-protect'
+registers of the SDRAM Serial Presence Detect EEPROMs.
+If you try and
+do a @command{i2cdump} on them to read the location, you won't get anything,
+because they contain a single write-only register.
+This register can be used to permanently
+write-protect the contents of the eeprom.
 
 
 @node Section 4.24, Section 4.25, Section 4.23, Problems