133-266mhz difference??

[takerm]

Ever since the 266mhz DDR ram has been released. It has been used with the 266mhz cpus from AMD. Now when the Atlon cpus first came out they used 100mhz ram and the cpu used the bandwith twice effectively making it 200mhz. Now that we have the choice of DDR 266 and SD 133. Wouldnt the 133mhz ram run at 266 which powers the 1333+ cpus. So i ow have to ask what is the reason for DDR until the cpus require a bus speed of 532mhz. Since you can run a 1400mhz athlon on pc133 ram which in australia is about 30-40 dollars cheaper than ddr ram. Can anyone help me get the idea of ddr as i really cant see a point with it until the 2.6Ghz+ cpus come out. I would be very greatful for any knowldge.

 

[Pabster]

It's true that with the current Thunderbird core, DDR only provides a 5-10% performance benefit over PC133, slightly higher in some areas but average is around 10%. However, the Palomino core makes far better use of DDR than Thunderbird. As well, with DDR being so cheap these days, and future boards being DDR-only, there's no reason to skimp by with PC133 on a new build.

 

[jpprod]

DDR SDRAM does in fact provide a significant performance advantage when you're bandwidth limited. The reasons why you don't see massive gains in majority of everyday software are

1. Bandwidth is only the other half of memory performance, and latency of DDR SDRAM isn't any better than equally clocked SDRAM's.
2. Memory is only one of the factors that determine real-world application performance, and it's impact varies from application to another. Whereas streaming tasks such as video encoding benefit noticeably from more bandwidth, computationally intensive tasks such as raytracing see little to no difference at all.

Also, since chipset's implementation of memory controller greatly affects latency, DDR SDRAM's real-world memory performance will improve as chipsets mature. Impressive benchmark results of the recently unveiled VIA KT266A are proof that we haven't seen the full potential of DDR SDRAM yet.

 

[soulm4tter]

here's a good example. Compare the KT133A which uses PC133 and the KT266A which uses DDR.

 

[Pederv]

It kinda sounds like you don't understand DDR. There are 2 speeds of DDR used as system memory PC1600 and PC2100. PC1600 is 200MHz DDR which runs on a 100MHz bus and PC2100 is 266MHz DDR which runs on a 133MHz bus, remember DDR means Double-Data-Rate. DDR memory is used in systems to try and get rid of the memory bottle-neck.

 

[Soccerman]

Now when the Atlon cpus first came out they used 100mhz ram and the cpu used the bandwith twice effectively making it 200mhz.

your CPU is connected to a chip called a NORTHBRIDGE through a bus called the FSB (front side bus). this chip also connects to the AGP port, and your system memory. the speed at which your RAM runs depends on the type. normal PC133 SDRAM runs at 133mhz. DDR SDRAM running at 133mhz (which is called PC2100) also runs at 133mhz, but provides what SDRAM would give if it was running at 266mhz.

With an Athlon running on a 100mhz fsb, the effective bandwidth that the fsb can handle is double what SDRAM running at 100mhz is capable of, so you typically aren't using the full bandwidth of the FSB (becuase the CPU normally interacts with the RAM, which is only capable of supplying the fsb with half it's full potential bandwidth, even though the SDRAM bus is running at full speed).

now, if you have DDR SDRAM running at 100mhz in the same situation, (this RAM is called PC1600) your RAM is finally capable of supplying the CPU with all the data that the fsb can handle, which means that the RAM is no longer nearly as big a bottleneck as before (the CPU would be sitting there waiting for data from the RAM alot more when not using DDR SDRAM).

that isn't to say that memory isn't a bottleneck or anything, it will always be too slow for CPU's to gain instantaneous access to it (whether the fsb is too slow, or the RAM itself is too slow), but every little bottleneck that is removed will provide a performance boost.