I, for one, thought you were clear. And Gerhard's concerns still apply. A 3 piston engine simply cannot be 'roughly equivalent' to a 5 piston engine. To make them 'roughly equivalent', the three piston engine would have to be somewhat faster than the five.
So, what kind of work would perform better on a faster 3 engine box and which would perform better on a slower 5 engine box? Given that the MSU ratings are the same, then, without any insight to the workload, one might have to call it a toss up. If the workload were very I/O intensive, then the 5 engine box might have a little edge in servicing while supporting a higher concurrent number of active tasks. I/O is CPU intensive, but concurrency might be advantageous. For a CPU intensive mix, then perhaps the faster 3 engine box might be the better choice. The very best of the season to you, yours, and theirs. -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Peter Duffy Sent: Monday, December 22, 2008 10:26 AM To: [email protected] Subject: Re: Performance Question for your collective consideration Hello, Gerhard, Perhaps I wasn't completely clear, how about substituting the word "equivalent" for "equal"? Can you consider choosing now? I used the concept of MIPS being about the same to be a short hand for the amount of measurable work done by the 3 CPU system is about the same as the 5 CPU system, MSUs, MIPS etc all are about the same number. If you had a pile of money to spend on one of two ROUGHLY equal boxes, one with 3 available CPUs and the other with 5, that being the only practical difference, which would you want, given the workload I described and the potential for some growth by adding fairly large workloads to the machine probably necessitating upgrades. Thanks, /ptd On Fri, Dec 19, 2008 at 5:47 PM, Gerhard Adam <[email protected]> wrote: > > > > If you had two machines, equal MIPS z10 BC boxes, would you want the box > > with 5 CPUs or the one with 3 CPUs? Memory, etc all equal. > > > > Well therein lies your problem. They are NOT equal machines and the reason > why this comparison is incorrect is because you're using that nonsense > metric MIPS. > > If we use your example and simply said that the total machine configuration > was 600 MIPS, then the one machine would actually be a 5 x 120 MIPS machine > and the other would be a 3 x 200 MIPS machine. They would be quite > different in the power available for any given set of instructions. > > This is only one reason why MIPS is such a bad number to use and is > generally so completely misunderstood. The most obvious point is that if > 600 MIPS were the power available, then it is clear that this is wrong since > no single unit of work could actually use it. > > Adam > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: GET IBM-MAIN INFO > Search the archives at http://bama.ua.edu/archives/ibm-main.html > ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html NOTICE: This electronic mail message and any files transmitted with it are intended exclusively for the individual or entity to which it is addressed. The message, together with any attachment, may contain confidential and/or privileged information. Any unauthorized review, use, printing, saving, copying, disclosure or distribution is strictly prohibited. If you have received this message in error, please immediately advise the sender by reply email and delete all copies. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
