I am wondering I have a P4 running at 533mhz FSB and have a board that will go up to a 800mhz FSB and processor support. I just bought some 400mhz memory and I am assuming that I will not get true 400 speed from it until I put a new 800mhz processor in correct? Sandra says my memory is only at the 333mhz currently. Too things will it hurt my new PC3200 to be clocked down and run at a lower speed while I currently run a 533mhz processor? Also if it is ok to keep the faster memory in the system clocked down then if I were to put my old stick of PC2700 back in along with the PC3200 would there be an issue with frequency? Would all run at 333 speed and work fine together? I just dont want to mess up my PC3200 because I plan to get a 800mhz processor in the next few months. thanks

Let me preface this by saying I'm an AMD guy...my experience with P4 systems is extremely limited... You can run your PC3200 at a lower speed without any ill effects, but unless your RAM's throughput (bandwidth) meets or exceeds that of the CPU, you're hurting performance. From what I've read, the P4 system actually performs a little better when the RAM's throughput exceeds the CPU's bandwidth. In other words, you have to look at it in terms of bandwith. With a 533FSB (133mhz x 4) CPU, the bandwidth is approx 4266mb/sec. To match the RAM's throughput to the CPU's bandwidth, you'd need at least PC2100 RAM in dual channel mode (2100mb/sec x 2) running at 133mhz. With an 800FSB CPU, the bandwidth would be 6400mb/sec, so you'd need at least PC3200 in dual channel mode (3200mb/sec x 2) running at 200mhz. With your current 533FSB CPU, you'd want your RAM's throughput at 4200mb/sec or higher. If your PC2700 & PC3200 are capable of running together in dual channel mode (& I don't know if they are or not), you should run them as either PC2100 (133mz) or PC2700 (166mhz). Here's where it gets a bit tricky (if it isn't already). There should be a CPU:RAM ratio setting in the BIOS. If the ratio is set to 1:1, the CPU & RAM will run at the same base bus speed (133, 166, 200mhz)...but there should also be several other choices. With the CPU FSB at 533, the base speed is 133mhz, so at 1:1, the RAM would also be running at 133mhz, which would be the equivilent of PC2100 (no matter what speed RAM you actually have installed). If you wanna bump the RAM speed up to 166mhz (equivilent of PC2700), you'd have to change the CPU:RAM ratio to 5:4...that would put your RAM's throughput in dual channel mode at 5400mb/sec (2700 x 2). I know this is confusing & I'm doing my best to explain the theory...am I making any sense?

Hey thanks for the quick reply and yes it does make sense. I have figured out with the board if you don't have a 800mhz processor installed then the memory will be locked if you will by the BIOS to only provide speed at 166 (x2) even if it is PC3200. I tried to override the RAM frequency in the BIOS and force it to run at 200 (x2) and it would not boot. I am ok to run it all meaning the full 1.024 GB for now at 166 until I buy a new CPU. Thanks again.

Jam, that was a good post, and I think you are slowly coming over to Intels cpus.(joke) Just a point to make and I dont know if its revelent, my board supports 266/333/ddr400 and cpu 400/533/800 fsb . Now I have a 800fsb cpu with 3200 DDR 400 all is well but the manual graph says no no no to using pc 3200 with the 400 or 533 cpu.So bowing to your better knowledge but at the same time query that the memory would work at all. I in my ignorance allways thought that if the motherboard accepted a higher frequency memory than the cpus fsb it would allways run at the lower of the two, but not where a board excluded these combinations. The multiplier is locked isnt it? but you can pump the fsb . Tell me have I got this garbled?

Forgot this question, would altering the frequency of the ram downwards overcome this.

"Jam, that was a good post, and I think you are slowly coming over to Intels cpus" 1st of all, it's jam, not Jam! LOL 2nd, the only Intel CPUs I ever touch are the 166/200/233MMX socket 7 variety ;) 3rd, on to your question...unforunately, I can't answer why PC3200 can't be used on the slower FSB...maybe one of the Intel guys will jump on it. It's seems to me it would work, but maybe there's something built into the architecture that prevents it

Hi jam ,Thanks for replying anyway.The board that would not accept it was a MSI 848p neo for anybody that might know.