DW aligned address

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DW aligned address

Postby Guest »

Hi,

I am not getting clearly that why first two bits of address are always zero.
Guest
 

Re: DW aligned address

Postby support »

The short, and most correct answer is: Because the standard says so.

The rationale behind this is that all bus accesses are done in DWs. If a bus entity needs to perform an operation at a smaller granularity, it is forced to use the Byte Enable bits, under pretty strict restrictions.

Think about the PCIe as an emulation for good old PCI: There were 32 physical data wires, physically connected to 32 data wires of some memory module. If the address wouldn't be DW aligned, there would be a need to route each of these data wires to four inputs of the memory module.
support
 
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