Memory timings

[grassy]

Hello,

Was is the order of importance (increased performance)of these timings, RAS, RCD, RP, CAS latency? In other words, which would increase the most performance by lowering the number? Right now I have 7-2-2-2.5 with 2x256MB Samsung PC3200 on a Shuttle A35N nforce2 with 1700 XP (plan to overclock the fsb to 200mhz).

 

[lhgpoobaa]

If i recall correctly the Cas number is pretty important, followed by the RAS with high speed modules.

For best performance see if you can run all the timings at their lowest.

Also, boosting the voltage by 0.1v or 0.2v can often lead to more stable operation at high speeds with hard timings.

MEMTEST86 is the program of choice for ram stability testing.

<b>Regards,
Mr no integrity coward.</b>

 

[grassy]

I now have the timings at 4-2-2-2.5. Is it better to have something like 8-3-3-2.0 where the CAS is 2.0? I have not increased the voltage yet.

 

[pIII_Man]

try to get all of the numbers as low as they can go!

If i put my k6 in a Ferrari it would be faster than your your pentium 4 or Athlon XP :tongue:

 

[pIII_Man]

i would consider the latter a little better...

If i put my k6 in a Ferrari it would be faster than your your pentium 4 or Athlon XP :tongue:

 

[Praesul]

I´m running my memory at 5-2-2-2, and get only a slight decrease when at 5-3-3-2!

---
The difference between theory and practise in practise is greater than the difference between theory and practise in theory.

 

[Praesul]

The 8-3-3-2.0 should perform better than 4-2-2-2.5.

---
The difference between theory and practise in practise is greater than the difference between theory and practise in theory.

 

[lwj81]

Your biggest increase will come from going to 200fsb.(sync).8-3-3-3.0 at 200fsb will outperform 5-2-2-2.0 at 166fsb.

 

[lhgpoobaa]

ard to tell. Each timing has a variable effect.
You should try varying them and doing some benchmarks.

You should really have a lookie here:
<A HREF="http://www.rojakpot.com" target="_new">http://www.rojakpot.com</A>
This guy does a very comprehensive bios guide that has more info than what i could ever give.

<b>Regards,
Mr no integrity coward.</b>

 

[bum_jcrules]

Master Poo is correct.

They are valued differently. Some that are very important you haven't even mentioned.


Just so all are on the same page...

DRAM CAS# Latency (JEDEC symbol = tCAS)

DRAM RAS# Precharge (JEDEC symbol = tRP)

DRAM RAS# to CAS# Delay (JEDEC symbol = tRCD)

DRAM Precharge Delay (JEDEC symbol = tRC or also known as "Bank Cycle Time")


Most people talk about tCAS settings until they are blue in the face. Most of the time there are only once cycle savings per read. Not a lot to write home to mother about. But hey, one cycle is one cycle.


Normally though people don't talk about tRAS violations. Okay, so what the heck is a tRAS violation. It come from this... tRAS + tRP = tRC. If you set tRC too low you will have tRAS violations. So if you have tRAS set at 3T (T being number of clock cycles) and tRP being set at 3T then you <b>NEED</b> a tRC setting of at <b>LEAST 6T</b>. You generally will need one to two more cylces more just to make sure you don't have tRAS violation errors. One should be sufficient but at higher clock speeds there are problems caused by hysteresis. (Go to <A HREF="http://hyperphysics.phy-astr.gsu.edu/hbase/solids/hyst.html" target="_new">this link</A> to understand more about the physics behind hysteretical loops and phase changes.... blah, blah, blah.) All other latency settings are based around the same problem of materials, phase changes, and the speed at which things can go back to their ground states.


Here are two other settings that you have not mentioned. Some motherboard BIOS' don't let you change these and some do. Either way you should know what they are if you want better performance. These are very important yet very much so overlooked by the "Joe Overclocker" let alone the average computer user.


The first is the <b>DRAM Idle Timer</b>. This should be set at 16T or 64T. This will be trial by error. Either should work but one will be better than the other. All of the other setting values should be disregarded.


The second is the <b>DRAM Refresh Mode</b>.
This should be set according to the maximum density that you are using. If you are going to use 1GB or more this should be set at 7.8 ƒÝsec and if it is less then 1GB set it at 15.6 u.sec. JEDEC stipulates that it should be 64 u.sec but this will depend on the stability of the system. You can set it at any one of the three. The longer the better the system will performance will be. However if you start using larger capacities (More MB/GB) then you will NEED to refresh more often.


So I hope this is a help.




Hey... you people in or near Toronto... Go to the LAN below!!!


Live near Toronto and like to game but you can't make it to Quakecon?
<A HREF="http://www.lanmash.com" target="_new"><b>LANMash2 is the same weekend 300+ gamers!</b></A>

 

[pIII_Man]

how does the dram idle timmer effect sdr sdram...i have that option in my bios...

How many bits are in a nibble?

 

[Praesul]

Who ever said to leave it at 166MHz FSB??? LOL Set it to CAS 5-3-3-2.0 and see what FSB you can make it stable at, probably better than running at CAS 3.0!

---
The difference between theory and practise in practise is greater than the difference between theory and practise in theory.

 

[bum_jcrules]

Basically what the idle timmer does is to track the number of cycles that a page is allowed to remain open if there is no access to it. In "most people's" systems you should have it set in a range between 16 and 64 cycles. Normally those are two of the setting values. (16 an 64) The reason you keep them open for specific periods of time is so if you are going back to a specific page you can do it with less latency clocks because the page is still open. If the page closes you have to wait to reopen the page. It means added latency penalties to do the same job.

If you are going to run server specific applications you would rather have this setting set really low. This is because the server is most likely not going back to the same page. You have more random reads. So shutting down the page right after it is read will allow the controller to be able to move on without being slowed down by having to shut a page and then open another. The random reads are thus done with less latency or what I should really say is better managed latency.

So depending on what kind of setup you have you will set it accordingly. Most likely you will set if for an intermediate timing like I stated above.



Live near Toronto and like to game but you can't make it to Quakecon?
<A HREF="http://www.lanmash.com" target="_new"><b>LANMash2 is the same weekend 300+ gamers!</b></A>

 

[lwj81]

He said he planned on overclocking to 200fsb.Thats all he needs to do to get the biggest increase.There is very little he will gain whatever he sets his timmings at.Sure,go as low as you can with the timmings but they have little effect compared to raising the fsb.

 

[pIII_Man]

TY


Proud owner of DOS 3.3

 

[bum_jcrules]

My pleasure... anytime.





Live near Toronto and like to game but you can't make it to Quakecon?
<A HREF="http://www.lanmash.com" target="_new"><b>LANMash2 is the same weekend 300+ gamers!</b></A>

 

[grassy]

Thank you, that helped a lot.