[Memory]Timings Constraints

Memory modules are defined by their frequency. The DDR400 running at 200MHz, this value known by everyone, there is reason to talk about timings. The timings values are a bit strange for beginners : DDR400 22,210 which is in fact 2/2/2/10 or the CAS, RAS to CAS, RAS and Cycle values. Memory is a kind of large matrix .

These values are waiting time before an information is given

CAS: Column Address Strobe or delay access column
RAS to CAS delay between modes column and row
RAS: Row Address Strobe or delay access row
Cycle time: time for a new round of access.

The more the response time is low, the better the performance. While it is possible to obtain correct timings at 200MHz (2.5/3/3/8) with inexpensive modules, you should pay much more for those who bear 2/2/2/5 at 200MHz. More than 250MHz, it is generally limited to 3/4/4/8. The first thing to do to achieve a high memory bus is to add high values to these parameters. A module intended to work at 200Mhz in 2.5/3/3/8 can generally operate at 220MHz but in 3/4/4/10 for example. By increasing the voltage of memory modules, it is possible to operate at more aggressive timings or higher frequencies. By default, the DDR works 2.5V and it is possible to push the voltage by10% or 2.75v. In addition, the modules may (over) heat and should be given r dedicated ventilation. Some high-performance modules are based on a voltage of 2.75v and can withstand more than 3v ...