RE: Memory Read as first transaction for lock operations

["Sudeep Dennis" <sudeep.dennis@wipro.com>]

The use of lock transaction is for the following reason: Suppose, you want to modify a particular location with a value of 50, only if the present value is 20. When you read the location you might get 20 as the value. But, how are you sure that somebody else will not write a new value into it, in the gap where you read the location(to get 20) and subsequently write(50) into it. 

A lock transaction helps you to hold that particular memory location from being accessed from anybody else from the period of your read to the time when you write. For this reason, lock transactions invariably start with a read.



-----Original Message-----
From:	Arti Gupta [mailto:arti.gupta@dcmtech.co.in]
Sent:	Thu 12/5/2002 2:05 PM
To:	pci-sig@znyx.com
Cc:	
Subject:	Memory Read as first transaction for lock operations

Hi,

Can anyone tell me why the memory read is the first transaction of the locked 
transactions?

Regards
Arti.





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