Decoupled Address and Data Bus

[lifez@sinewave]

Hi,
"Decoupled address and data buses support split-bus transaction
capability for improved bandwidth"
This is the Statement in one of the Specs Given, I want to Know
1. What is Decoupled Address??
2. Wat is Split Bus Transaction??

How they Improve Bandwidth???

Regards,
RP Yadav

 

[gabor]

On Mar 10, 6:35 am, "lifez@sinewave" <ramesh.pal.ya...@gmail.com>
wrote:

Hi,
"Decoupled address and data buses support split-bus transaction
capability for improved bandwidth"
This is the Statement in one of the Specs Given, I want to Know
1. What is Decoupled Address??

I think they mean the address bus is "decoupled" from the data bus.

In other words the address on the address bus on a particular cycle
does not necessarily correspond to the data on the data bus on
that cycle.

2. Wat is Split Bus Transaction??

This usually refers to a bus transaction that starts with a
request of some sort (for example "read address 1234") and
then terminates with a completions of some sort (for example
"the data at location 1234 is 5467"). In-between the
request and completion, the transaction doe not make use of
the bus.

How they Improve Bandwidth???

Generally by allowing multiple access to the bus without
waiting for transaction completion. For example if there
were three bus masters trying to read 3 different bus locations
at the same time, and the memory was very slow, each bus
master would briefly use the bus to make its request,
followed by the memory (eventually) returning each of
the requested pieces of data. Without split transaction,
each bus master would need to wait for the memory to
complete the read cycle requested by the previous master,
possibly while the bus sat in some "busy" state.

Regards,
RP Yadav