You're referring to CAS latency which is the actual response time of the memory. A gamer will look for maximum bandwidth speed with the lowest latency, and adjust the settings find a balance in between. Over-aggressive settings of either will lead to instability, however these are system bios tweaks that take a computer user much deeper than the usual user wants to go. Good quality ddr2 might run default at 5-5-5-15 timings. DDR3 offers greater bandwidth speed, but comes with a higher latency (7ish), so the actual real world difference right now is minimal and not worth the extra cost. Absolutely get a processor running at 1333mhz with a motherboard that can run the fsb at the same speed! Faster, no bottleneck between chipset (that is if your motherboard does 1333). They also run cooler than the 1066mhz processors. The fastest ram you'll benefit from is quality pc6400 as well, such as this: http://www.buy.com/retail/product.asp?sku=202541818&ref=lmcd (It used to be $60AR.) This ram will run at the default speeds that your 1333mhz processor is running at with room to bump them up as well. Many people are successfully setting their CAS down to 4, and sometimes 3 with this memory as well. These settings are important to overclockers, those who are trying to maximize their current system's performance potential. If you want to learn more, read this (a few times): http://forums.anandtech.com/messageview.aspx?catid=28&threadid=2057083&enterthread=y Currently I'm running an e6850 on an Abit IP35 Pro motherboard at 3.78ghz instead of 3ghz. I have pc8500 but would have been fine with pc6400. (This is a direct 25% calculation-performance increase over stock.)
The penalty for ECC over non-ECC memory is < 3%, being closer to 0% in actual operation. In the case that it's actually corrected/detected an error do you care about a slight increase in latency? To build an extremely reliable trading platform you need to have high-reliability/quality in each part. Power supply, motherboard, memory... It's also not just "stability" we're talking about but "data integrity" as well. If your processing is cpu-intensive the memory latency isn't that important. We're not talking gamers here. They live at the extreme-speed edge not the extreme-reliability edge.
ECC is slower, period. Its slower for workstations, its slower for servers. It depends on the activity if someone will notice it, but is basically never recommended for workstations. If you want stability from your memory, get a high quality line from a name brand memory manufacturer like Corsair, Crucial, Gskill, Patriot, Kingston, Ocz, Mushkin...(all of which are capable of producing crap as well)...but ECC will not help stability for a traders workstation. This is primarily imo because memory sticks these days are not where instability generally occurs in a stock system.) And actually, its very easy to have excellent stability with middle of the road parts, like what Dell usually uses, as long as they aren't constantly stressed with high loads and high heat. Even trader workstations are generally far less than 100% cpu utilization most of the time, but of course that varies. Btw, since you only get the best and make stability the priority, what does the rest of your system look like? What OS, cpu/cpu cooler, chipset/pwm cooling, power supply, motherboard, case/fan ventilation are you using? Or did you buy it from Dell? I'm not trying to be facetious, but if someone is going to work towards optimal stability, all of these things imo are valuable to address well before thinking that ecc memory will improve stability.
To add...I totally agree stability in a trader workstation is extremely critical...but that's what a reliable motherboard with all japanese capacitors addresses, a psu that keeps very stable voltages, after-market performance cooling keeping all of temps very reasonably low, even under load, excellent memory/memory modules, and a case that ventilates incredibly well with 120mm fans (and of course winXP). Ecc imo just isn't in the same spectrum for addressing stability concerns.
My current trading computer is actually a Dell server with ECC running Windows XP. It is run 24x7 and is extremely reliable. As you allude to, ECC is only part of the reliability equation. The weak realibility-links in most computers are probably a sub-standard power-supply or sub-standard electrical power (which makes a UPS an important part of the reliability equation also).
You're motherboard might actually require ecc, so naturally that may play a significant role in your system's stability. It sounds like your configuration is working very well for you and that's what counts. Great trading to you.
I will let you in on a little secret. I used to work for one of the major computer company. We have engineer tests to show that ECC is a total waste of money. Of course the report was not published, nor should you believe what I am telling you on an anonymous public forum. If ECC gives you peace of mind, I would encourage you to go for it.
Actually no, it can use unbuffered Ecc or non-Ecc. To you as well, unless you are trading against me...