> 4) The chipset for P4 systems is in a state of flux at the moment. There are > several available but only two worth considering: i850e and e7205. The > differences here are substantial e.g. i850e supports 533 MHz RDRAM (PC1066) > whereare the e7205 supports dual-channel DDRAM. Actually the theoretical > memory bandwidth are the same - but DDR is much cheaper & easier to obtain. > Also the e7205 chipset, and only the e7205 chipset, supports hyperthreading. > > Systems using single-channel DDRAM memory will be considerably slower with > the same clock speed - probably 10-15%. The way I look at it, the ~$200 > required to buy a 10% faster processor is better spent on a more efficient > memory subsystem. Same applies with RDRAM - using "cheap" PC800 RDRAM in a > system which supports PC1066 is a very bad compromise.
The newest DDR systems, i845pe, run the DDR at 166/333Mhz, and SDRAM including DDR is 8 bytes wide, so this gives a memory burst speed of 333*8 = 2.6Gbyte/sec. RDRAM is only 32bits wide, so 1066*4 = ~4GB/second. However, DDR SDRAM still has lower latency than RDRAM, so this partially compensates for the slower burst rate. Btw, Intel says the i845pe supports P4 hyperthreading. Those E7xxx family chipsets are server grade, and generally quite expensive. The 7505 is for dual Xeon processors. Now, the regular P4 flat out doesn't support dual CPU operation, so if you want to build a multiprocessor, the Xeon is your only choice, and the E7505 is the entry level chipset for that. They use dual bank 266Mhz DDR ram, which requires ECC registered DDR, which costs somewhat more than regular DDR (say, $110 per 512MB). AFAIK, the Xeon offers very little advantage over the newer P4 in single CPU systems. Xeon processors require a 'wind tunnel' cooling solution, they have large passive heatsinks and rely on externally ducted airflow (and a LOT of it). The 2U dual Xeon servers I just built for work are *NOISY*. 512MB of 333Mhz DDR is around $70. 512MB of 1066 RDRAM is ~ $230. i845pe boards run in the $100-120 range unless they have a lot of extras like ieee1394 and/or SATA and/or ATA RAID onboard. i850e boards run $160 and up (same caveats as above). cheapest E7505 based board I can find is $500 (Intel SE7505VB2) regular P4 2.4Ghz for $178, 2.53 for $213, 2.66 for $266, and 2.8 for $388. Xeon 2.4 are $263, 2.6 are $338, and 2.8 are $528. some base systems (mobo, cpu, ram only)... p4B 2.66G + 1GB 333MHz DDR + i845pe = $516 p4B 2.66G + 1GB 1066 RDRAM + i850e = $886 Xeon 2.6 + 1GB registered DDR + e7505 = $1038 the Xeon will most likely require a server grade chassis with lots of cooling fans. (all prices based on a local dealer and solutions4sure.com) _________________________________________________________________________ Unsubscribe & list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
