Memory JEDEC spec - how to understand that?

[Wody 0]

Hello,another question before I order:The configurator of my shop gives me a warning for this memory:GeIL DIMM 4 GB DDR2-1066 Kit (2 pcs.)4096 MB, CL5 5-5-15, 2, PC2 8500The Mainboard is a: Asus P5Q PRO Intel

[jordanal 70]

They are simply gaurenteeing the ability of the sticks to run at 1066 @ 5/5/5/15 if you set the timings and FSB by hand in the BIOS. They never bothered to update the JEDEC table on the chips so they're offering to do the manual BIOS settting for you. For a fee of course, I'm sure.... Not very hard to do if you've made BIOS tweaks yourself sometime in the past.Before you buy this RAM however, I suggest you find NickN's Tuning thread at the bottom of my sig and go down to the memory section to make sure the timings are proper for DDR2800/1066. Off the top of my head, I think DDR2800 timings should be lower for quality RAM for FS. He just added this 'RAM - Timings' table to his tuning thread the other day.

[Wody 0]

Al,thanks!according to NickN's list my DDR2-1066 memory with 5-5-5-15 is ok. I could not get lower latencyWhat is the more important spec the 1066 vs 800, or is the latency more important (5-5-5-15 vs 4-4-4-12).I could also get a DDR2-800 kit with 4-4-4-12.Also, how does FSB frequency and timings for memory correlate? This I did not understand yetThanksPeter

[jordanal 70]

Think of the DDR2 speed and timings as a matched set. Nick's table guides you to maximum timings for a given DDR rating. Otherwise, you're buying generic, non-performance RAM at a given FSB/DDR rating. His is the first table I've seen spec'ing timings from DDR2-800 all the way up to DDR3-2000. I think off the top of my head, I would get the 1066 (5/5/5/15) stick over the DDR2-800, but that's just me.You raise the CPU multiplier and/or the FSB to set or overclock a system. As you raise the FSB, it affects the stability and capability of the given DDR RAM. You are pretty much setting or overclocking the CPU and the RAM at the same time when changing the FSB, to a point of instability. Then, as you tighting (lower) the timings of the RAM, the performance (bandwidth) increases to a point of affecting stability again. Too tight of timings will cause a overclock to fail. This is why you pay for quality RAM, to get decent timings at a given DDR/FSB setting.Look around at some of the overclocker forums. Search for guides and little calculators that guru's sometimes put together to get an idea how one BIOS setting affects another. Overclockers.net and Xtremesystems.com are two that come to mind as good sites. Get your system built and stable with the spec'd settings. Then use tools like CPU-z, RealTemp, OCCT, Prime95, LinX, MemTest, and MemSet to begin OC'ing or even setting minor tweaks like tightening the RAM timings at the default sysetm specs.Hope this helps...

[Guest Nick_N]

Al,thanks!according to NickN's list my DDR2-1066 memory with 5-5-5-15 is ok. I could not get lower latencyWhat is the more important spec the 1066 vs 800, or is the latency more important (5-5-5-15 vs 4-4-4-12).I could also get a DDR2-800 kit with 4-4-4-12.Also, how does FSB frequency and timings for memory correlate? This I did not understand yetThanksPeter

In FSX the faster the memory speed @ the lowest timing wins, but there are some things a user must understand about clocking as well when it comes to pre-i7 systems whereby the northbridge memory controller is itself hindered by latency.Assuming your system will in fact run 1066 @ 5-5-5 you are better off on that than 800 @ 4-4-4 however the difference between those two in DDR2 when a user is not clocking the CPU correctly can be small. Its when the user applies the correct CPU STRAP/FSB that the northbridge latency drops allowing the CPU cache and physical memory to communicate much faster and with that the system/FSX can take far greater advanatge of the higher memory speed and timingFor a user to really take as much advanatge as possible of the higher memory speed a FSB of 400 (min) and a CPU STRAP of 333 (or 400 depending on the proc) must be used. Therefore the clock needs to be calculated by the user before purchase to be sure the installed CPU/HSF will run the mentioned settings stable/cool. i7 does not require such prep because the memory controller is located in the processor and therefore the 'wait state'issue does not exist at the same level on that platform.Now I will say this.. the difference with all of the above and DDR2 800/1066 is there but no where near as great a difference if a user moves to DDR3 (ex; DDR3 1333 5-5-5 or 1600 6-6-6)DDR2 is really very limited once you get up into the 800-1066 range and there is nothing a user can do with it that will ever provide the same result correctly spec'd DDR3 will (1st or 2nd generation DDR3). The industry is no longer producing the 'cherry bin" DDR2 timing chips that ran 800 @ CAS3 and 1066 @ CAS4