Technical Reference Guide
Compaq Deskpro 4000N and 4000S Personal Computers
First Edition - September 1997
8-13
8.4.5 DIMM SUPPORT
The BIOS includes DIMM support consisting of the following:
♦ Access control with the serial (I
2
C) EEPROM of the DIMM
♦ Runtime information on ECC-correctable single bit errors
♦ POST message if ECC-correctable errors are detectable during POST memory test
DIMMs with 128 bytes of EEPROM can be used although 256-byte EEPROM DIMMs are
recommended for full support of Compaq intelligent manageability features. The following BIOS
functions have been added to provide specific support of DIMMs:
INT 15h AX=E827h, BH=00h; Read DIMM EEPROM
ENTRY: AX = E827h
BH = 00h
BL = DIMM No. (0-3)
CX = Number of bytes to read
DX = Offset of first byte to read
DS: (E) SI = Address of data buffer to receive data
RETURN: CX = No. of bytes read
CF = 0 (Success)
AH = 0
1 (Failure)
AH = Error Code:
01h, No DIMM EEPROM or socket empty
02h, Boundary error (offset or no. of bytes to read exc. cap)
86h, Not supported
INT 15h AX=E827h, BH=01h; Write DIMM EEPROM
ENTRY: AX = E827h
BH = 01h
BL = DIMM No. (0-3)
CX = Number of bytes to be written
DX = Offset of first byte to be written
DS: (E) SI = Address of data buffer holding write data
RETURN: CX = No. of bytes written
CF = 0 (Success)
AH = 0
1 (Failure)
AH = Error Code:
01h, No DIMM EEPROM or socket empty
02h, Boundary error (offset or no. of bytes to read exc. cap)
86h, Not supported
INT 15h AX=E827h, BH=02h; Get ECC-Corrected Single Bit Error Status
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