From widmer@us.ibm.com Wed Dec 1 14:17:48 1999 Received: from ruebert.ieee.org (ruebert.ieee.org [199.172.136.3]) by gatekeeper.pdd.3com.com (8.9.1/8.9.1) with ESMTP id OAA27819; Wed, 1 Dec 1999 14:17:45 GMT Received: by ruebert.ieee.org (8.9.3/8.9.3) id IAA22437; Wed, 1 Dec 1999 08:35:29 -0500 (EST) From: widmer@us.ibm.com X-Lotus-FromDomain: IBMUS To: stds-802-3-hssg@ieee.org cc: mritter@us.ibm.com, jfewen@us.ibm.com, jenkins@lsil.com Message-ID: <8525683A.004AA09A.00@D51MTA07.pok.ibm.com> Date: Wed, 1 Dec 1999 08:35:08 -0500 Subject: Short Reply to Note by R. Taborek `Hari Byte vs. Word Striping' dated 26 Nov. 1999. Mime-Version: 1.0 Content-Disposition: inline Sender: owner-stds-802-3-hssg@ieee.org Precedence: bulk X-Resent-To: Multiple Recipients X-Listname: stds-802-3-hssg X-Info: [Un]Subscribe requests to majordomo@majordomo.ieee.org X-Moderator-Address: stds-802-3-hssg-approval@majordomo.ieee.org X-Lines: 52 Status: RO Content-Type: text/plain; charset="us-ascii" Content-Length: 3000 Thank you for sharing your views on some issues related to the Hari interface. From your referenced treatise and prior statements, I get the impression that you are utterly confused about some fundamental as well as the detailed features of our proposal and you have seriously misrepresented, probably inadvertently, some aspects of it. Also, with respect to implementation and circuit questions, your evaluation criteria, preferences and value scales appear to be in conflict with what I think experienced designers in this area would normally judge as appropriate. So it is no surprise that some of your conclusions strike me as outlandish. Far more disturbing is the fact that you seem to be unable to arrive at a fair conclusion even where the differences are trivial and simple to understand. Just as an example, I cite your handling of item 9) Running Disparity Processing: I think, I am well qualified to evaluate this function, since for over 2 decades I have been involved with various codec designs and many individuals inside and outside my company have asked me for help . Quite recently, I have designed an 8B/10B codec for 12.5 Gbaud operation. So I know for sure, there is no significant difference in the coding area for byte or word striping, but there is a slight performance advantage for a word based codec because disparity prediction can be applied more effectively. With current technologies available to anyone, just four codecs are required for either case, the only difference is how they are ganged together which is utterly trivial. As you correctly point out, at the receiving end of each lane, the bit pattern must be checked for invalid characters and disparity violations and these circuits are identical to what is needed for disparity adjustment which requires just about 50 additional gates and the whole thing is less than a decoder with checks. It is also obvious that either a byte striped or word striped Hari can be connected to a scrambled or a 64B/66B coded link with comparable ease or difficulty. An 8B/10B coded 12.5 Gbaud link is also a viable option and both Hari versions have to adjust the disparity, but the byte striped version as currently defined has a known disadvantage because its Idle structure is ill suited for byte and word alignment at high speeds (It requires more complex pattern detection circuits with added delay in a critical area.) My recommendation would be to simply translate the current Hari Idle for transmission over the 12.5 Gbaud single lane to an Idle word resembling the Fibre Channel Idle . Based on these verifiable facts, it is hard to understand how you can justify the attribution of a bonus point for the current Hari version. We will reply soon with details and attempt to present a more balanced perspective on other issues as well. Albert Widmer Phone: 914 945-2047 email: widmer@us.ibm.com IBM T.J. Watson Research Center P.O. Box 218 Yorktown Heights, New York, 10598-0218