1Kernel driver eeprom
4Supported chips:
5  * Any EEPROM chip in the designated address range
6    Prefix: 'eeprom'
7    Addresses scanned: I2C 0x50 - 0x57
8    Datasheets: Publicly available from:
9                Atmel (,
10                Catalyst (,
11                Fairchild (,
12                Microchip (,
13                Philips (,
14                Rohm (,
15                ST (,
16                Xicor (,
17                and others.
19        Chip Size (bits) Address
20        24C01 1K 0x50 (shadows at 0x51 - 0x57)
21        24C01A 1K 0x50 - 0x57 (Typical device on DIMMs)
22        24C02 2K 0x50 - 0x57
23        24C04 4K 0x50, 0x52, 0x54, 0x56
24                                (additional data at 0x51, 0x53, 0x55, 0x57)
25        24C08 8K 0x50, 0x54 (additional data at 0x51, 0x52,
26                                0x53, 0x55, 0x56, 0x57)
27        24C16 16K 0x50 (additional data at 0x51 - 0x57)
28        Sony 2K 0x57
30        Atmel 34C02B 2K 0x50 - 0x57, SW write protect at 0x30-37
31        Catalyst 34FC02 2K 0x50 - 0x57, SW write protect at 0x30-37
32        Catalyst 34RC02 2K 0x50 - 0x57, SW write protect at 0x30-37
33        Fairchild 34W02 2K 0x50 - 0x57, SW write protect at 0x30-37
34        Microchip 24AA52 2K 0x50 - 0x57, SW write protect at 0x30-37
35        ST M34C02 2K 0x50 - 0x57, SW write protect at 0x30-37
39        Frodo Looijaard <>,
40        Philip Edelbrock <>,
41        Jean Delvare <>,
42        Greg Kroah-Hartman <>,
43        IBM Corp.
48This is a simple EEPROM module meant to enable reading the first 256 bytes
49of an EEPROM (on a SDRAM DIMM for example). However, it will access serial
50EEPROMs on any I2C adapter. The supported devices are generically called
5124Cxx, and are listed above; however the numbering for these
52industry-standard devices may vary by manufacturer.
54This module was a programming exercise to get used to the new project
55organization laid out by Frodo, but it should be at least completely
56effective for decoding the contents of EEPROMs on DIMMs.
58DIMMS will typically contain a 24C01A or 24C02, or the 34C02 variants.
59The other devices will not be found on a DIMM because they respond to more
60than one address.
62DDC Monitors may contain any device. Often a 24C01, which responds to all 8
63addresses, is found.
65Recent Sony Vaio laptops have an EEPROM at 0x57. We couldn't get the
66specification, so it is guess work and far from being complete.
68The Microchip 24AA52/24LCS52, ST M34C02, and others support an additional
69software write protect register at 0x30 - 0x37 (0x20 less than the memory
70location). The chip responds to "write quick" detection at this address but
71does not respond to byte reads. If this register is present, the lower 128
72bytes of the memory array are not write protected. Any byte data write to
73this address will write protect the memory array permanently, and the
74device will no longer respond at the 0x30-37 address. The eeprom driver
75does not support this register.
77Lacking functionality:
79* Full support for larger devices (24C04, 24C08, 24C16). These are not
80typically found on a PC. These devices will appear as separate devices at
81multiple addresses.
83* Support for really large devices (24C32, 24C64, 24C128, 24C256, 24C512).
84These devices require two-byte address fields and are not supported.
86* Enable Writing. Again, no technical reason why not, but making it easy
87to change the contents of the EEPROMs (on DIMMs anyway) also makes it easy
88to disable the DIMMs (potentially preventing the computer from booting)
89until the values are restored somehow.
93After inserting the module (and any other required SMBus/i2c modules), you
94should have some EEPROM directories in /sys/bus/i2c/devices/* of names such
95as "0-0050". Inside each of these is a series of files, the eeprom file
96contains the binary data from EEPROM.

Archive Download this file