pc3200 vs pc2700 RAM question

[BBill]

I had an AMD Athlon XP 2000 processor go bad after the cpu fan failed.
So to fix it it bought an AMD Athlon XP 3000 (2.17ghz) and an AMD suggested Motherboard (Gigabyte 7VT600P-RZ).

After successfully installing I called Gigabyte tech support to make sure I had all of the motherboard settings tweaked for maximum speed because it seems to run a bit faster than the XP 2000 but not almost twice as fast.

I had everything set right. I told the tech that I still had PC2700 ram and that I was going to upgrade that to PC3200 RAM which should speed things up. The mboard supports pc2100, pc2700 and pc3200.

The Tech said that upgrading to PC3200 RAM would not increase performance here becasue the XP 3000 has a 333MHZs bus speed.

I'm not a processor or memory expert, but I find this interesting. I thought you could never have fast enough memory.

Is this tech guy right? Is pc3200 a waste of money here?

[tinhat]

The CPU bus speed to the RAM is the limiting factor (in this case). Any capability above that is unused.

If your spec is accurate your CPU fsb is 166MHz. Because it uses DDR it accesses RAM on both edges of the clock, meaning that effectively the bus runs at 333MHz. A 333MHz bus uses PC2700 to its peak capability but although PC3200 likely will still work it runs at the same data rate as a PC2700. (fsb * 2 * 8B ~= 2656MB/s, a.k.a "pc2700"; solving for 3200 gives a fsb speed of 200MHz).

If your CPU spec is correct the tech guy is right.

Mike

PS Don't confuse "capacity" with "capability". More RAM capacity is almost always better and can speed up a system suffering from too little. If you're not sufferring from too little RAM no extra amount can speed your system up.

PPS Also understand we're talking about switching cycles on the order of billionths of a second. The difference between the two RAMs you ask about honestly is entirely imperceptible to a human being even if you could make use of pc3200.

[MyMindIsGoing]

The Athlon XP 3000 (2.17ghz) uses 333mhz bus and pc2700 memory. The other version of XP 3000 (2.1ghz) uses 3200, so he was right.

http://www.amd.com/us-en/assets/cont...docs/26237.PDF

[tinhat]

[ QUOTE ]
The Athlon XP 3000 (2.17ghz) uses 333mhz bus and pc2700 memory. The other version of XP 3000 (2.1ghz) uses 3200, so he was right.

http://www.amd.com/us-en/assets/cont...docs/26237.PDF

[/ QUOTE ]

Not trying to be a dick I hope you'll understand (I just think this stuff is cool) but it doesn't actually say "333MHz" - it says "333 FSB". Notice pg 21 specifies the clock's period as 6ns - that's 166MHz. So their own spec says the fsb is cycled at 166MHz and not 333MHz ("t1" in the diagram shows a period as one pos edge and one neg edge as you'd expect).

So this is just a naming gimmick of AMD's - I wonder if Intel does the same?

[MyMindIsGoing]

They send two signals per cycle, making it "fast as 333" although only 166. Yes Intel does the same, their 800mhz bus is not 800mhz.

[BBill]

tks - appreciate all the input.
I was considering getting an Athlon 64 3000+ which was about the same price but newer technology. But the 64 3000 runs at about 1.9 ghz and the xp runs at 2.16.

The 64 has a total bus speed of 2000mhz

In any case I decided that faster (xp) must be better. Its working pretty well I was just hoping for more of a noticable performance boost.

From what I have read the athlon xp 3000 can be overclocked rather easily which can up the bus speed as well as the internal clock.