RE: initiator questions

["Weng Tianxiang" <WTX@umem.com>]

Hi,
My practice is the following:
1. After system starts, remember nPCIBus64B_R value from nREQ64;
2. Unless specially required, always issue commands with bus width of
nPCIBus64B_R value.
3. My design will response to nREQ64 of each transaction.

Weng Tianxiang

wtx@umem.com
wengtianxiang@yahoo.com

Micro Memory Inc.
9540 Vassar Avenue
Chatsworth, CA 91311
Tel: 818-998-0070
Fax: 818-998-4459




-----Original Message-----
From: Richard Iachetta [mailto:iachetta@us.ibm.com] 
Sent: Friday, November 09, 2001 2:19 PM
To: pci-sig@znyx.com
Subject: Re: initiator questions


>Beyond that, if you are doing a long burst that is broken up into 
>smaller bus transactions, you should keep trying to do the same bus 
>width that was accepted on the first bus transaction.

I'm not sure I agree with that.  If a transaction is disconnected by the
target (or even by the master for that matter), the master doesn't
really know if the continuation address will be to the same target or
another.

>Also, remember that it doesn't hurt performance to try a 64-bit burst 
>if the burst length is 4 DWORDs or longer, and the starting address has

>AD[2:0]==0.

Right, so why not just always try 64-bit?

Rich Iachetta
IBM Microelectronics Division -- Austin
World Wide Field Design Center
Phone: 512-838-6305   Tie Line: 678-6305