How much faster is CL2 vs CL2.5 vs CL3?

[Northland]

I'm looking at setting up a new box based on the Epox 8RDA+ with 1GB of PC2700 DDR and a Barton chip (not sure of which one yet). I've been lurking around PC's for a long time but don't know the answer to this question:

In the real world (not synthetic benchmarks) how much performance difference is there between CL2, CL2.5 and CL3? I'm a hardcore 3d gamer and just wonder how the performance would differ between these different memory types.

Thanks for your input,

Northland

 

[zsouthboy]

I too used to wonder about this, so i bought a stick of CAS 2 mushkin when i was building my new system, so i could test later on.

My findings? CAS 2 vs. CAS 2.5 (which are actually a cas latency of 4 and 5, respectively[because its ddr]).... CAS 2 has ~10% performance advantage.... IMHO, noticeable in games also, at least that much in UT2k3 and such. Now, the main issue of that little extra performance vs. the extra cost..... some might think its worth it, some may not.

 

[Northland]

zsouthboy: Thanks for the feedback. I guess I will have to take the crowbar out, use it on my wallet and buy some CAS 2!

Northland

 

[UnSean]

I found with my Corsair that it was worth running a lower overclocked FSB, to ensure that I can achieve cas 2 timings, the difference is very marked.
If you can definetely go for cas 2.

 

[WalMart1564]

i think were all agreed that cas2 makes a noticable diffrence

here is my question im building a comp using the same mobo

how much real world performace gain is pc2700 over 2100 assuming im usign a 266 fsb proc.
and is pc3200 worth it or will the bottleneck be my fsb ?

 

[zsouthboy]

Originally posted by: WalMart1564
i think were all agreed that cas2 makes a noticable diffrence

here is my question im building a comp using the same mobo

how much real world performace gain is pc2700 over 2100 assuming im usign a 266 fsb proc.
and is pc3200 worth it or will the bottleneck be my fsb ?

Your FSB is going to be your problem... using PC2700 will allow you to OC though .... and the PC3200 will take your memory out of the overclocking equation all the way up to 200 mhz FSB.

Personally, i would *try* to go for the 3200, gives you headroom in the future.

 

[Shalmanese]

(which are actually a cas latency of 4 and 5, respectively[because its ddr]).

Are you sure about this?

 

[TerryMathews]

Originally posted by: Shalmanese

(which are actually a cas latency of 4 and 5, respectively[because its ddr]).

Are you sure about this?

Depends on how you define CAS. From the Northbridge's perspective, it only takes two, 2.5, or three cycles to get an item from memory. If you look at this from the RAM, however, 4, 5, or 6 cycles are passing if you define cycle as an opportunity for the RAM to do something. Of course, this isn't the standard definition of cycle, but with some electronic devices capturing the clock signal two, three, or four times a cycle...

BTW, DDR catches the rising and leading edge of the clock signal. As does the Athlon's CPU bus. The P4, as I understand it, captures those two points, plus their inverses. Basically all the available signal change points.

 

[Shalmanese]

Oh, your talking about from the perspective of the RAM. but CAS 2 166Mhz DDR will have the same latency as CAS2 166Mhz SDR more or less right? (DDR is slighlty slower IIRC).

 

[Northland]

To begin with, thanks for all the helpful advice on this! I took the plunge and bought the following:

Epox 8RDA+ from Newegg for $109 shipped (price just dropped from $122). I could have purchased it a few dollars cheaper from some other sites but I have just had such good luck with Newegg it was worth a little more to go with them.

http://www.newegg.com/app/viewproduct.asp?DEPA=&submit=Go&description=8rda

Two Geil PC2700 256mb Ultra DDR Cas2 5-2-2-1T DDR sticks for $115 shipped from Googlegear. For about $20-$25 more per stick I could have purchased PC3200 Cas2 from Geil but didn't think it was worth it. With memory prices dropping like a rock I will purchase a pair of 512mb sticks in six months and toss these sticks in a backup machine. This is the best price I could find on this quality of memory by quite a bit.

http://www.googlegear.com/jsp/ProductDetail.jsp?ProductCode=80038


Now I just have couple more questions! Until the price of the Barton CPU's drops to a more reasonable level, I will be running an Athlon XP2000 Palomino.

With the Epox 8RDA+, will I be able to run 166 FSB with a mutilplier of 10 with the memory running synchronously at 333Mhz? If this works then I assume I would be free to bump the multiplier and FSB higher until I run out of overclocking headroom.

Would I be better off just picking up a thoroughbred XP1700 from Newegg for $55 and putting my Palamino in a backup machine? Will this likely overclock higher? What is the difference between an A and a B thoroughbred and how do you know which one you will get?


Thanks for all the help on these questions.

Northland