Intel® Core™ Ultra 200H and 200U Series Processors

Datasheet, Volume 1 of 2

ID Date Version Classification
842704 05/27/2025 Public
Document Table of Contents

Boot Block Update Scheme

The Processor supports a “Top-Block Swap” mode that has the Processor swap the top block in the SPI flash (the boot block) with another location. This allows for safe update of the Boot Block (even if a power failure occurs). When the “top-swap” enable bit is set, the Processor will invert A16 for cycles going to the upper two 64-KB blocks in the appropriate address lines.

For SPI when top swap is enabled, the behavior is as described below. When the Top Swap Enable bit is 0, the Processor will not invert any address bit.

Boot Block Update Scheme

BOOT_​BLOCK_​SIZE Value

Accesses to

Being Directed to

000 (64KB)

FFFF_​0000h - FFFF_​FFFFh

FFFE_​0000h - FFFE_​FFFFh and vice versa

001 (128KB)

FFFE_​0000h - FFFF_​FFFFh

FFFC_​0000h - FFFD_​FFFFh and vice versa

010 (256KB)

FFFC_​0000h - FFFF_​FFFFh

FFF8_​0000h - FFFB_​FFFFh and vice versa

011 (512KB)

FFF8_​0000h - FFFF_​FFFFh

FFF0_​0000h - FFF7_​FFFFh and vice versa

100 (1MB)

FFF0_​0000h - FFFF_​FFFFh

FFE0_​0000h - FFEF_​FFFFh and vice versa

101 - 111

Reserved

Reserved

Note:This bit is automatically set to 0 by RTCRST#, but not by PLTRST#.

The scheme is based on the concept that the top block is reserved as the “boot” block, and the block immediately below the top block is reserved for doing boot-block updates.

The algorithm is:

  1. Software copies the top block to the block immediately below the top
  2. Software checks that the copied block is correct. This could be done by performing a checksum calculation.
  3. Software sets the “Top-Block Swap” bit. This will invert the appropriate address bits for the cycles going to the SPI.
  4. Software erases the top block
  5. Software writes the new top block
  6. Software checks the new top block
  7. Software clears the top-block swap bit
  8. Software sets the Top_​Swap Lock-Down bit

If a power failure occurs at any point after step 3, the system will be able to boot from the copy of the boot block that is stored in the block below the top. This is because the top-swap bit is backed in the RTC well.