th MRL and MRM bus commands r for increasing bus perfomance in case of burst cycle. the only constraint in :
MRL is : master has to start cycle with address and byte enables such that reading till cacheline shouldnt be a problem, as master wants to read till cacheline.(giving stress on the point that it is illegal to read upto between any two cacheline boundary using MRL/MRM)
for target, it shud not give disconnect before cacheline size i.e buffer pipelines shud keep pumping data till cachelinesize.
MRM is : this bus command is for reading multiple cachelines. target can give disconnects at cachesize only.
i hope i was on right track and u can work out with that...do get back if any problem...
ASIC Design Engineer
DCM Technologies INDIA
Phone : 91-11-5719967
Extn : 216/286 (O)
Email : email@example.com
Sent: Monday, April 03, 2000 7:09 PM
Subject: Memory Read Line and Memory Read Multiple
Hello PCI experts,
1. Can anybody shed some light on the usage of the PCI commands
Memory Read Line and Memory Read Multiple?
2. If a master (i.e. initiator) on a PCI expansion board
uses one of these commands to read motherboard memory in
long bursts, does it need to know something about the structure
of the cache on the other side of the bridge?
3. If the Memory Read Line
command is used, is it illegal to try to read past the cacheline
4. How about with Memory Read Multiple, what if the
master decides to terminate the transfer before the cacheline
boundary is reached? Is this illegal? If not, what is the
purpose of the distinction between these commands?
5. How does the behaviour of a master that uses one of these
commands differ from one that uses the ordinary Memory Read