On 29 Oct 2001, at 19:30, Henk Stokhorst wrote: > [... snip ...] However it has already been > implemented in the latest version (v21). That version contains more > improvements so I wondered if it wouldn't be a good idea to inform > users through the occasional newsletter. Particulary because it gives > a 10% improvement for Pentium I, II and III users and it skips P-1 if > it has been done.
Umm - I haven't noticed any significant improvement in v21 speed on Pentium or Pentium II - the big changes are implementing prefetch, which is only applicable to AMD Athlon family, PIII and faster Celeron processors, and exploiting the SSE2 instruction set on Pentium 4 only. Apart from (sometimes) skipping P-1, the changes between v20 and v21 are pretty well cosmetic if you're using a 486 / Cyrix / AMD K6 / Intel Pentium (Classic or MMX) / Pentium Pro / Pentium II / Celeron < 533 MHz CPU. There _are_ some other changes - including a bit of fine tuning of the exponent / FFT run length size breaks - but nothing which really makes an upgrade look inescapable. In fact, these older systems are more likely to have a memory constraint than newer systems with faster processors; due to the inclusion of the Pentium 4 specific SSE2 code, the v21 binary has a significantly bigger memory footprint, so systems which won't benefit from the prefetch code & which are feeling memory pressure might be better _not_ upgrading. The speed improvement from v20 to v21 on a PIII or Athlon system should be somewhere close to 25%, rather than 10%. On these systems an upgrade seems highly desirable. If you're still running v20 (or earlier) on a Pentium 4, then quite frankly you really SHOULD upgrade. NOW. The execution speed will approximately treble. As for "reduced participation" - whilst other reasons certainly do have an effect, I've previously mentioned two other possible reasons: (1) adverse publicity stemming from the prosecution of a sysadmin for running RC5 clients on "his" systems without the agreement of the management at the college which employed him; (2) steep rises in electricity prices and unreliability of supply in some places e.g. USA West Coast deterring people from running extended jobs. Regards Brian Beesley _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
