0x39D0

0x39D0

0x39D0 is a hexadecimal value that appears in the documentation of several embedded‑controller families and in a number of low‑level operating‑system sources. The figure represents a memory address that is conventionally used as the starting point of a fixed function block within the device’s internal memory map. In many 8‑bit microcontrollers, for example those based on the 8051 core, 0x39D0 marks the beginning of the interrupt vector table for external interrupts. At this address the processor expects to locate a short jump instruction that forwards execution to the appropriate service routine. The table entries are located in the range 0x39D0 through 0x39DF, providing eight vectors in total.

In the Linux kernel, the same hexadecimal offset is referenced in the source of the Linux on Intel 9250 platform support. It denotes the boundary between the standard BIOS data area and the extended memory reserved for BIOS extensions. The firmware developers typically reserve this area to store configuration flags that are read by the boot loader. This use case is similar to the vector‑table usage in microcontrollers, where the offset marks the start of a region that contains first‑level control data for the system.

The value also shows up in the ACPI (Advanced Configuration and Power Interface) specification as an offset used by some motherboard firmware to locate the Root System Description Pointer (RSDP) within extended BIOS data. Because the register layout is identical across various BIOS implementations, 0x39D0 is often cross‑referenced by developers as a shorthand for the start of the ROM and BIOS data area.