On Sunday 18 August 2002 17:18, you wrote: > What a difference RAM makes. > > I didn't find my specific configuration on the benchmarks page, so I am > sending in this. > > CURRENTLY on the benchmarks page: > > Athlon XP1800+, 1533 Mhz, 133 DDR, L2=256-Full, 15-17M timing: 0.091 sec
The memory access speed matters a lot, too. Most PC2100 (133/266 MHz DDRAM) is CL2.5 but premium PC2100 memory can work at CL2. PC2700 (166/333 MHz DDRAM) usually works at CL2 when run at PC2100 speeds. The difference between DDRAM @ CL2 compared with CL2.5 is about 5%. Your benchmark speed sounds about right for CL2 DDRAM; I'm getting 0.097 sec on a Athlon XP1700+ using CL2.5 PC2100 DDRAM with a very mild overclock (nominal voltages, FSB wound up to 136 MHz, i.e. CPU clock 1496 MHz). Similarly PC133 (SDRAM) can be either CL2 or CL3, with CL3 around 8% slower. > > I have a virtually identical machine, except it is using mere 133 Mhz > SDRAM. I'm CERTAIN the CPU bus speed is correct, and that the L2 is fully > enabled, yet for an exponent smack in the middle (in the 16 millions) I'm > getting only 0.116 sec out of it, on a barren (i.e fresh install, no other > apps/services running) W2K machine (v22.7 beta). > > That's a TWENTY TWO PERCENT performance hit, just for not using DDR! Sounds a lot, I'd have expected around 15% ... did you check the other performance settings in the BIOS? These can make a significant difference... (If you turn off the L2 cache the speed will drop DRAMATICALLY. Factors of 20 or more are typical!) One thing that _doesn't_ seem to make a whole lot of difference is the FSB speed. I have two Athlon T'bird 1.2GHz systems, both running in Abit KT7A mobos with the same RAM (CL2 SDRAM @ 133 MHz) and the same BIOS tuning. The difference is that one of the CPUs is 12x100 and the other is 9x133. There is less than 1% difference in speed between the two systems. This may be relevant with the new Pentium 4 "A" (quad-pumped 100 MHz) & "B" (quad-pumped 133 MHz) variants - my guess is that a "A" variant coupled with 533 MHz memory is going to outperform a "B" variant coupled with 400 MHz memory by some margin. Obviously a "B" with 533 MHz memory is going to be best. Note also that RDRAM outperforms DDRAM by a considerable margin. The problem is that 533 MHz (PC1066) RDRAM is hard to obtain and therefore expensive at present. However spending $100 extra on better memory is going to be a lot more effective in performance terms than spending $100 extra on the processor, once you're at the top end of the range. > > A word to the performance wonks out there -- use the BEST RAM that your > motherboard can take advantage of. And it gets more and more important as the clock speeds go up. > > One of these days I'll drop some DDR in there (sad to say, I don't have any > spare right now), and see if it truly does drop down to 0.091 or > thereabouts. Note that it is not often possible to use SDRAM or DDRAM in the same board. SDRAM DIMMs are 168 pin, DDRAM DIMMs are 184 pin, so the modules are not physically interchangeable. Unless you have two sets of RAM slots, you aren't going to be able to convert without swapping the mobo. Even then I doubt you will be able to use both DDR and SDR at the same time, without crippling the DDR performance to SDR levels. Regards Brian Beesley _________________________________________________________________________ Unsubscribe & list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
