BIOS Information show ROM Size 0MB

[EmmettTsai]

dmicode ouput:

emmett@emmett:~/project/github/mirror/dmidecode$ sudo ./dmidecode -t 0
# dmidecode 3.6
Getting SMBIOS data from sysfs.
SMBIOS 3.3.0 present.

Handle 0x000F, DMI type 0, 26 bytes
BIOS Information
	Vendor: Microsoft Corporation
	Version: 24.203.143
	Release Date: 08/16/2024
	ROM Size: 0 MB
	Characteristics:
		PCI is supported
		BIOS is upgradeable
		BIOS shadowing is allowed
		Selectable boot is supported
		EDD is supported
		Japanese floppy for NEC 9800 1.2 MB is supported (int 13h)
		Print screen service is supported (int 5h)
		8042 keyboard services are supported (int 9h)
		ACPI is supported
		USB legacy is supported
		BIOS boot specification is supported
		Targeted content distribution is supported
		UEFI is supported

I read the raw data of rom size of BIOS Information from /dev/mem :
(09h) BIOS ROM Size: 0xFF
(18h) Extended BIOS ROM Size: 0x0000

According Specification:
BIOS Information (Type 0)
(09h) BIOS ROM Size Description:

Size (n) where 64K * (n+1) is the size of the physical device containing the BIOS, in bytes.
FFh - size is 16MB or greater, see Extended BIOS ROM Size for actual size

Since BIOS ROM Size is 0xFF, so the result is greater or equal to 16MB,
and Extended BIOS ROM Size is zero, not greater then 16MB,
hence the result should be 16MB.