Note that, contrary to most EEPROMs (SPD, EDID), Vaio EEPROMs don't seem to have no checksum. Here is a summary of what I have understood so far.
Note that I am not actively maintaining this page, so the information found here may be wrong for recent Sony Vaio laptops.
| Offset | Length | Value | Meaning |
|---|---|---|---|
| 0x00 | 7 | Encoded string | System password, if set. Filled with 0x00 if the password is unset. Note that the password is not necessarily completely overwritten on change. If you change a long password for a shorter one, the end of the initial password may still be there after the new, short password and its trailing 0x00. |
| 0x07 | 7 | Encoded string | User password, if set. Same encoding as the system password. Not all systems have this second password. Systems that have not have either all 0x00 or all 0xFF. |
| 0x0E | 1 | 0x00 or 0xFF | Probably no special meaning. |
| 0x0F | 1 | Security options | 0xFF or 0x4E (Japanese model) means that you are required to enter the password at boot time. 0xFE or 0x00 means you don't have to. |
| 0x10 | 16 | Binary | The system's UUID. The last six bytes match the internal Ethernet adapter's hardware address. The first eight bytes are supposed to reflect the time at which the UUID was generated, and the two bytes in the middle are randomly generated. |
| 0x20 | 16 | String | Some OEM data. I originally thought that the first two bytes were referring to the continent the system was sold on (EU for Europe, UC for North America, JP for Japan), but since then I've seen Europeran models starting with "JP" so I'm no longer sure. The rest is unknown. This string appears as OEM String 1 in the DMI table. |
| 0x30 | 80 | 0xFF or 0x00 | Nothing. |
| 0x80 | 32 | String | The machine name, with the PCG- or VGN- prefix. Used to end with the country code in parentheses (FR for France, GB for Great Britain, DE for Germany, UC for United States of America, J for Japan), but no longer. |
| 0xA0 | 10 | String | Revision (e.g. 01) or service tag (e.g. A2224D2J). |
| 0xAA | 4 | String | First half of the asset tag. By default, this is the 4-characters model name, without the PCG- or VGN- prefix. I can't say why there is a model name that differs from the machine name. Only a digit can be found at first and third positions, while either a digit or a letter can be found at second and fourth positions. Model names in a given family (e.g. GRX) have similitudes, but I hardly can say more. |
| 0xAE | 12 | Binary | Second half of the asset tag. Depending on the model, the asset tag may appear in the DMI table as Chassis Asset Tag or as OEM String 3. The asset tag can't be changed in the BIOS, and it seems that Sony has been selling custom asset tags as a service at some point in time. |
| 0xBA | 2 | 0xFF or 0x00 | Nothing. |
| 0xBC | 1 | 0x00, 0x01 or 0x02 | Unknown. |
| 0xBD | 1 | 0x04 or 0x05 | Unknown. The value 0x04 was seen on a Japanese model, the value 0x05 was seen on European and North-American models. |
| 0xBE | 1 | 0x05, 0x65, 0x75 or 0x95 | Unknown. |
| 0xBF | 1 | Binary | Unknown. |
| 0xC0 | 32 | String | The serial number. All serial numbers seen so far are made of 7 or 8 digits, followed by an hyphen, followed by 7 digits, for a total of 15 or 16 bytes. The other 16 bytes are probably reserved for future changes in the serial numbering scheme. |
| 0xE0 | 18 | String | A timestamp, probably the production date and time of the EEPROM (and thus of the laptop) or maybe the date and time of the first run. The date is in Anglo-Saxon notation (month/day/year) but the time is in ISO-8601 notation. |
| 0xF2 | 10 | 0x00 or 0xFF | Nothing. |
| 0xFC | 4 | Binary | Unknown. Most often filled with 0x00 or 0xFF (unused) but sometimes the byte at 0xFC holds a real value (seen: 0x01, 0x03). |
Here comes a map of the EEPROM, with question marks for values that differ between the different samples I've seen. Red stands for unknown fields while green means known ones. Grey represents unused fields. The values that do not differ from model to model can be used for identification purposes.
0 1 2 3 4 5 6 7 8 9 a b c d e f 00: ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? 10: ?? ?? ?? ?0 ?? ?? 11 ?? 8? ?? 0? ?? ?? ?? ?? ?? 20: ?? ?? ?? ?? ?? 3? ?? ?? ?? ?? ?? 00 00 00 00 00 30: ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? 40: ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? 50: ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? 60: ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? 70: ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? 80: 5? 4? 4? 2d ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? 90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 a0: ?? 3? ?? ?? ?? ?? ?? ?? 00 00 3? ?? 3? ?? ?? ?? b0: ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? 0? 0? ?5 ?? c0: 3? 3? 3? 3? 3? 3? 3? ?? ?? 3? 3? 3? 3? 3? 3? ?? d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 e0: 3? 3? 2f 3? 3? 2f 30 3? 20 3? 3? 3a 3? 3? 3a 3? f0: 3? 00 ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??
I would like to thank everyone who helped me gathering this information.