From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from nommos.sslcatacombnetworking.com (nommos.sslcatacombnetworking.com [67.18.224.114]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTP id E4AEB679F5 for ; Wed, 8 Mar 2006 03:03:43 +1100 (EST) In-Reply-To: <002b01c641ff$666ccc70$6405a8c0@absolut> References: <002b01c641ff$666ccc70$6405a8c0@absolut> Mime-Version: 1.0 (Apple Message framework v746.2) Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Message-Id: <7C2FA1F5-DF91-495E-A2C3-052048E34DFE@kernel.crashing.org> From: Kumar Gala Subject: Re: GNU and Freescale MPC83xx / e300 core support? Date: Tue, 7 Mar 2006 10:03:53 -0600 To: Russell McGuire Cc: linuxppc-embedded@ozlabs.org List-Id: Linux on Embedded PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mar 7, 2006, at 9:54 AM, Russell McGuire wrote: > Thanks all... > > The author of that comment humbly apologizes for his ineptitude on > the FPU. > > It would appear both cores have the same number of execution units, > i.e. 5 > So David, I guess in all this the only real difference seems to be > the bus > architecture, raw clock speed, and perhaps a few new instructions. > I checked > both manuals this morning and they do differ in some small ways. > > * 603e, up to 4 instructions in the pipeline, only 3 being complete > per > clock > * e300, up to 5 instructions in the pipeline, still only 3 being > completed > or start per clock. > * Add/compare instructions are now executed in the IU unit instead > of the > load/store unit. May be the same, but wasn't specific in earlier 603e > manuals. > * One more HID0 bit than G2, ability to interrupt based on cache > parity > error > * new icbt instruction, instruction cache initialization > > So there is a section inside the 8360E manual that outlines the > specific > enhancements. "Features specific to the e300 core not present on > the G2 > processors follow:" Page 1-5. > > So I guess my question is back up, does anyone know if an optimized > compiler > would offer any noticeable performance enhancements in regards to > these > changes? Other than the obvious instruction being added? If you are asking about relative performance between the same compiler tuned for a 603 vs e300, the there would most likely be a small improvement. However, a few things to note. The new icbt instruction is really intended for hand written assemble code and its highly unlikely that a compiler will ever generate it. Second, the other improvements from the base 603e/G2LE in 8280, like doubling of the L1 caches has a significant improvement in performance. - kumar