Specifications

Code Definitions
115
must be filled in prior to EfiCompatibility code issuing the Compatibility16 function
Compatibility16InitializeYourself().
Compatibility16InitializeYourself() is defined in Compatability16
Functions.
LastpciBus
Maximum PCI bus number assigned.
UmaAddress
Start Address of Upper Memory Area (UMA) to be set as Read/Write. If
UmaAddress is a valid address in the shadow RAM, it also indicates that the region
from 0xC0000 to (UmaAddress – 1) can be used for Option ROM.
UmaSize
Upper Memory Area size in bytes to be set as Read/Write. If zero, no UMA region
will be set as Read/Write (i.e. all Shadow RAM is set as Read-Only).
HiPermanentMemoryAddress
Start Address of high memory that can be used for permanent allocation. If zero,
high memory is not available for permanent allocation.
HiPermanentMemorySize
Size of high memory that can be used for permanent allocation in bytes. If zero,
high memory is not available for permanent allocation.
UMA Address and Size
UmaAddress UmaSize Conclusion
0 0
• Shadow RAM 0xC0000-0xDFFFF is used for Option ROMs.
• No Shadow RAM is set as Read/Write.
0 S (<> 0)
• Shadow RAM 0xC0000-0xDFFFF is used for Option ROMs.
• No Shadow RAM is set as Read/Write.
N (<> 0) 0
• If N is a valid address in Shadow RAM 0xC0000-0xFFFFF
a. Shadow RAM 0xC0000 to (N – 1) is used for Option ROMs.
b. No Shadow RAM is set as Read/Write.
• If N is not a valid address in Shadow RAM
a. Shadow RAM 0xC0000-0xDFFFF is used for Option ROMs.
b. No Shadow RAM is set as Read/Write.
N (<> 0) S (<> 0)
• If the region from N to (N + S – 1) is a valid region in
Shadow RAM
a. Shadow RAM 0xC0000 to (N – 1) is used for Option ROMs.
b. Shadow RAM from N to (N + S – 1) is set as Read/Write.
• If the region from N to (N + S – 1) is not a valid region in
Shadow RAM
a. Shadow RAM 0xC0000-0xDFFFF is used for Option ROMs.
b. No Shadow RAM is set as Read/Write.