The IDPROM address space provides system information including Machine Type, Serial Number, Ethernet Address, and Manufacturing Date. This information may be stored in an IDPROM, NVRAM, or EEPROM. The 32 Bytes of IDPROM content are shown below.
| BYTE | FIELD | SIZE |
| 1 | Format | 1 Byte |
| 2 | Machine Type | 1 Byte |
| 3 | Ethernet Address | 6 Bytes |
| 4 | Date | 4 Bytes |
| 5 | Serial Number | 3 Bytes |
| 6 | Checksum | 1 Byte |
| 7 | Reserved | 16 Bytes |
The Machine Type and Serial Number are combined to create the Hostid. Licensed software may use the Hostid.
Prior to the SPARCstation 10, the Machine Type was used by the operating system to identify the architecture and the architecture implementation.
Beginning with the SPARCstation 10, systems are not assigned a unique Machine Type. The device tree in the Open Boot PROM provides the system characteristics to the operating system. The high-order bit of the Machine Type is set to 1. The lower 7 bits of the Machine Type and Serial Number fields are used at Sun's discretion.
The alpha-numeric code on the NVRAM barcode label can be used by Sun to create a duplicate NVRAM. Provide this information when ordering a replacement NVRAM.
IDPROMs, NVRAMs, and EEPROMs are not interchangeable.
Programmed components that have a unique machine type are not interchangeable. For example, a new NVRAM is required when an SS2 (55xxxxxx) is upgraded to an SS20 (72xxxxxx).
Different component types are not interchangeable between systems. For example, a new NVRAM is required when an SS4 is upgraded (48T08) to an Ultra 1 Model 140 (48T59).
The 48T08 and 48T18 have the same pin count as the 48T59 but they are not pin compatible with the 48T59.
The NVRAM also contains a Time of Day clock. Accuracy of the clock is typically +/- 1 minute per month at 25°C. The 32,768Hz oscillator is tested not to exceed +/- 1.53 minutes per month (35PPM) error rate at 25°C.

| ARCH | SYSTEM | HOSTID | COMPONENT TYPE | PART # | SOCKET |
| Sun-4 | 4/260/280 4/110/150 4/3xx 4/3xx 4/470/490 4/470/490 |
2100xxxx 22xxxxxx 23xxxxxx None 24xxxxxx None |
IDPROM IDPROM IDPROM 48T02 NVRAM IDPROM 48T02 NVRAM |
520-1532 520-1638 523-2136 100-1628 525-1100 100-1628 |
U1901 U805 U2202 U2200 U1404 U3505 |
| Sun-4c | SS1 SS IPC SS1+ SS SLC SS ELC SS IPX SS2 4E |
51xxxxxx 52xxxxxx 53xxxxxx 54xxxxxx 56xxxxxx 57xxxxxx 55xxxxxx 61xxxxxx |
48T02 NVRAM 48T02 NVRAM 48T02 NVRAM 48T02 NVRAM 48T02 NVRAM 48T02 NVRAM 48T02 NVRAM 48T02 NVRAM |
525-1032 525-1084 525-1109 520-2749 525-1188 525-1180 525-1112 523-8151 |
U089 U0901 U089 U1011 U0813 U0512 U0512 U1101 |
| Sun-4m | SPARCclassic X SPARCclassic SS LX SPARC Xterm 1 SS4 SS5 SS10 SS10SX SS20 SS600MP SS Voyager JavaStation |
80xxxxxx 80xxxxxx 80xxxxxx 80xxxxxx 80xxxxxx 80xxxxxx 72xxxxxx 72xxxxxx 72xxxxxx 71xxxxxx 80xxxxxx 80xxxxxx |
48T08 NVRAM 48T08 NVRAM 48T08 NVRAM 48T08 NVRAM 48T08 NVRAM 48T08 NVRAM 48T08 NVRAM 48T08 NVRAM 48T18 NVRAM 48T08 NVRAM 48T08 NVRAM 48T08 NVRAM |
525-1343 525-1203 525-1203 525-1391 525-1391 525-1369 525-1184 525-1184 525-1378 525-1181 525-1373 525-1657 |
U0707 U0707 U0707 U1605 U1605 U1506 U1004 U1004 U1004 U2701 U1506 U1505 |
| Sun-4d | SS1000/1000E SS1000/1000E SS1000/1000E SC2000/2000E SC2000/2000E SC2000/2000E |
80xxxxxx 80xxxxxx 80xxxxxx 80xxxxxx 80xxxxxx 80xxxxxx |
EEPROM 48T08 NVRAM 48T08 NVRAM EEPROM 48T08 NVRAM 48T08 NVRAM |
100-2922 100-3528 100-4195 100-2922 100-2822 100-4195 |
U0209 U1007 U1007 U0203 U1205 U1205 |
| Sun-4u | A11 A12 A14 |
80xxxxxx 80xxxxxx 80xxxxxx |
48T59 NVRAM 48T59 NVRAM 48T59 NVRAM |
525-1430 525-1430 525-1417 |
U2006 U2006 U2006 |
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