Path: ...!weretis.net!feeder8.news.weretis.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Terje Mathisen Newsgroups: comp.arch Subject: Re: Byte Addressability And Beyond Date: Wed, 5 Jun 2024 12:21:01 +0200 Organization: A noiseless patient Spider Lines: 35 Message-ID: References: <2024May29.090435@mips.complang.tuwien.ac.at> <20240603132227.00004e0f@yahoo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Wed, 05 Jun 2024 12:21:02 +0200 (CEST) Injection-Info: dont-email.me; posting-host="f84ce4f3a433bc91a4eab9bf3aa5b9f4"; logging-data="988813"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1/Gs/1mg7ohnFsq0B7/m7L7AFccSHvD+JSTR4mZXtVACQ==" User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Firefox/91.0 SeaMonkey/2.53.18.2 Cancel-Lock: sha1:vN9BcDBXA1Ie8P144RvxKOukpPc= In-Reply-To: Bytes: 3000 MitchAlsup1 wrote: > Terje Mathisen wrote: > >> > >> That logic already exists, in the form of a single thread/core >> dedicated >> to the job. > >> With 30-100 cores on a single die, it becomes very cheap to dedicate >> one >> of them to babysit such a process, compared to the cost of making a >> custom chunk of VLSI to do the same. This is particularly true because >> the logic needed in the babysitting process is mostly straight line, >> with a very limited number of hard-to-predict branches. > >> I.e. h.264 CABAC decoding has three branches per bit decoded, at least >> one of them impossible to predict or work around with clever coding. > > How many instructions in the then-clause and in the else-clause ?? > If these are smaller than 8, My 66000 can process them without > "branching" using predication. No, the real problem is the context branching: After doing the 50% branch you pick up one of two alternative contexts and follow totally different paths, i.e. you cannot simply use the branch bit as an index. I found ways to bypass the issues with the other two branches but this one is fundamental. Terje -- - "almost all programming can be viewed as an exercise in caching"