Originally Posted by Kopi
Im hoping you guys could tell me a little bit more about ram timings and what they do. Currently they are 2.5,3,3,7
This is intended to address P4 Ram Timings and should not be viewed as an AMD Athlon64 memory post.
RAM timings are the 2 - 2 - 2 - 5 --> 3 - 4 - 4 - 8 that you are speaking of when you mention your 2.5 - 3 - 3 - 7. What do these numbers really mean? They actually refer to the delay timings of DRAM. Now less delays mean faster DRAM speeds. So the lesser (tighter) the timings/delays, the faster is the RAM. Meaning 2 - 2 - 2 - 5 is faster than 3 - 4 - 4 - 8. One must keep in mind that all the above assumes that the clockspeed of the RAM remains the same with only the timings being changed.
These are the most common RAM timings for a P4 mainboard. Strobe? Remember your Quadratic Equations or Statistics? The Parabola? The time it takes for one Parabolic curve is the strobe function. Beginning to end and the time it takes to achieve this is a strobe timing.
DRAM Timing Selectable (Options - Manual, By SPD)
This refers to the settings of the 3 timings I will explain below. By SPD means that the timings are set by the BIOS automatically to the default suggested by the manufacturer. The timings in By SPD mode can be used as a reference/default. Since you want to tweak the settings, set this to Manual.
CAS Latency Time (Options - 2, 2.5, 3)
This refers to the Column Address Strobe delay time. Lower is better! However, in a P4 system, lowering this setting only improves performance minimally, so it might be better to increase this setting to gain stability or a higher overclock.
Act to Precharge Delay (Options - 5, 6, 7, 8)
This refers to the Active to Precharge delay time. Lower is better! However, same as above, lowering this setting only improves performance minimally, so it might be better to increase this setting to gain stability or a higher overclock.
DRAM RAS# to CAS# Delay (Options - 2, 3, 4)
This refers to the Row Address Strobe to Column Address Strobe delay time. Lower is better! This is the most crucial setting in a P4 system! Lowering this setting improves performance quite noticeably, so you might want to sacrifice some clockspeed to lower this timing.
DRAM RAS# Precharge (Options - 2, 3, 4)
This refers to the Row Address Strobe to Column Address Strobe delay time. Lower is better! This is the 2nd most crucial setting in a P4 system! Lowering this setting improves performance quite noticeably, so you might want to sacrifice some clockspeed to lower this timing.
When someone refers to RAM timings as 2 - 3 - 4 - 5, they usually mean, from 1st number to the last number:
- 2- CAS latency time
- 3- RAS# to CAS# delay
- 4- RAS# Precharge
- 5- Act to Precharge Delay
Keep in mind that if you lower the RAM timings too much, your system be unstable or might not boot. If this happens, turn off your computer and wait at least 30 seconds. Just press and hold the INSERT key when turning on your PC again and all should be fine.
Different RAM sticks are made for different things.
- Some RAM sticks are built for lower clockspeeds and tight timings. For example, DDR 400 with 2 - 2 - 2 - 5 timings. However, RAM like this can seldom reach high clockspeeds.
- Some are built for super-high clockspeeds and more relaxed/higher latencies. For example DDR500 with 3 - 4 - 4 - 8 timings. These RAM usually cannot run at super tight timings, but can achieve speeds of 250MHz or more.
- There is always a compromise between clockspeeds and latency. Lower latencies usually mean lower clockspeeds. Higher clockspeeds mean higher latencies.
- Timings and clockspeeds affect the performance of the RAM. So, the perfect RAM will be able to run at super high clockspeeds (DDR500+), and at super low latencies (2 - 2 - 2 - 5) in a perfect ram time world however DDR500+ and 2 - 2 - 2 - 5 do not exist, hence the need for other methds (DDR2/DDR3) to achieve faster speeds in DRAM.
Props to demol1sh3d
for his excellent DRAM Timings FAQ