作业:Cache Initial Considerations
*Memory Address可能对应的元件种类或属性:
1,DRAM
2,Shadow RAM
3,SMRAM
4,VGA RAM Buffer
5,IO Devices'Registers
6,BIOS ROM or RAM on PCI/LPC Bus
请问以上在Cache Initial时应该考量的因素为何?
*CPU的Instruction Fetch也是一种Memory Read Cycle
*CPU的Data Bus有64bits,一般的Memory Data Read是8-16-32bit
*Instruction Fetch一次可能连续读64Bytes,不管会不会被执行到
*BIOS ROM,不管是ISA,LPC,FWH,or SPI ROM,都是只有8-bit Data
*对CPU而言,BIOS ROM是个相当慢速的Device
*当系统开机或S3 Resume时,CPU一定是从BIOS ROM开始执行
*CPU自BIOS ROM Fetch Instruction执行的速度是非常的慢
*BIOS必须尽早将Address 0f0000-0fffffh设定成Cacheable