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most agressive memory timings for epox 8k3a+

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June 23, 2002 5:17:09 PM

just built a new system with epox 8k3a+ axp 2100+ winxp pro, corsiar pc 3000 cas 2.0 and i was wondering what the most agressive memory timings are for this board, there are a lot more options than in my asus board so i'm not sure what to use:

SDRAM cycle length: 2, 2.5, 3 this i know should be 2
Bank interleave: 2 bank, 4 bank, disabled (no clue)
precharge to active (trp): 2t, 3t
active to precharte (tras): 5t, 6t
active to cmd (trcd): 2t, 3t
dram burst length: 4, 8
dram queue depth: 4 level, 2 level, 3 level
dram drive strength: auto, manual
dram command rate: 1t, 2t
dclkI/O timing: 0ns, .5ns, 1ns, auto
fast r-w turn around: enabled, disabled
continuous dram request: enabled, disabled

that's all that listed for the memory, also i have the option of the following system performance profiles:
normal, fast, fastest, turbo..what's the difference and which should i use?
Anonymous
a b à CPUs
a b } Memory
June 24, 2002 8:52:51 AM

SDRAM CAS Latency Time
Options : 2, 3

This controls the time delay (in clock cycles - CLKs) that passes before the SDRAM starts to carry out a read command after receiving it. This also determines the number of CLKs for the completion of the first part of a burst transfer. In other words, the lower the latency, the faster the transaction.

Note that some SDRAM modules may not be able to handle the lower latency and will become unstable and lose data. Therefore, set the SDRAM CAS Latency Time to 2 for optimal performance if possible but increase it to 3 if your system becomes unstable.

Interestingly, increasing the CAS latency time does have an advantage in that it will enable the SDRAM to run at a higher clockspeed, thereby giving you an edge in overclocking your system. So, if you hit a snag while overclocking, try increasing the CAS latency time.



SDRAM Cycle Time Tras/Trc

Options : 5/6, 6/8

This feature toggles the minimum number of clock cycles required for the Tras and the Trc of the SDRAM.

Tras refers to the SDRAM's Row Active Time, which is the length of time in which the row is open for data transfers. It is also known as Minimum RAS Pulse Width.

Trc, on the other hand, refers to the SDRAM's Row Cycle Time, which determines the length of time for the entire row-open, row-refresh cycle to complete.

The default setting is 6/8 which is more stable and slower than 5/6. The 5/6 setting cycles the SDRAM faster but may not leave the row open long enough for data transactions to complete. This is especially true at SDRAM clockspeeds above 100MHz.

Therefore, you should try 5/6 for better SDRAM performance and only increase it to 6/8 if your system becomes unstable or if you are trying to get the SDRAM to run at a higher clockspeed.



SDRAM RAS-to-CAS Delay

Options : 2, 3

This option allows you to insert a delay between the RAS (Row Address Strobe) and CAS (Column Address Strobe) signals. This delay occurs when the SDRAM is written to, read from or refreshed. Naturally, reducing the delay improves the performance of the SDRAM while increasing it reduces performance.

Therefore, reduce the delay from the default value of 3 to 2 for better SDRAM performance. However, if you are facing system stability issues after reducing the delay, reset the value back to 3.



SDRAM RAS Precharge Time

Options : 2, 3

This option sets the number of cycles required for the RAS to accumulate its charge before the SDRAM refreshes. Reducing the precharge time to 2 improves SDRAM performance but if the precharge time of 2 is insufficient for the installed SDRAM, the SDRAM may not be refreshed properly and it may fail to retain data.

So, for better SDRAM performance, set the SDRAM RAS Precharge Time to 2 but increase it to 3 if you face system stability issues after reducing the precharge time.



SDRAM Cycle Length

Options : 2, 3

This feature is similar to SDRAM CAS Latency Time.

This controls the time delay (in clock cycles - CLKs) that passes before the SDRAM starts to carry out a read command after receiving it. This also determines the number of CLKs for the completion of the first part of a burst transfer. In other words, the lower the latency, the faster the transaction.

Note that some SDRAM modules may not be able to handle the lower cycle length and will become unstable and lose data. Therefore, set the SDRAM Cycle Length to 2 for optimal performance if possible but increase it to 3 if your system becomes unstable.

Interestingly, increasing the cycle length does have an advantage in that it will enable the SDRAM to run at a higher clockspeed, thereby giving you an edge in overclocking your system. So, if you hit a snag while overclocking, try increasing the SDRAM Cycle Length.



SDRAM Leadoff Command

Options : 3, 4

This option allows you to adjust the leadoff time needed before the data stored in the SDRAM can be accessed. In most cases, it is the access time for the first data element in a burst. For optimal performance, set the value to 3 for faster SDRAM access times but increase it to 4 if you are facing system stability issues.



SDRAM Bank Interleave

Options : 2-Bank, 4-Bank, Disabled

This feature enables you to set the interleave mode of the SDRAM interface. Interleaving allows banks of SDRAM to alternate their refresh and access cycles. One bank will undergo its refresh cycle while another is being accessed. This improves performance of the SDRAM by masking the refresh time of each bank. A closer examination of interleaving will reveal that since the refresh cycles of all the SDRAM banks are staggered, this produces a kind of pipelining effect.

If there are 4 banks in the system, the CPU can ideally send one data request to each of the SDRAM banks in consecutive clock cycles. This means in the first clock cycle, the CPU will send an address to Bank 0 and then send the next address to Bank 1 in the second clock cycle before sending the third and fourth addresses to Banks 2 and 3 in the third and fourth clock cycles respectively. The sequence would be something like this :-

CPU sends address #0 to Bank 0
CPU sends address #1 to Bank 1 and receives data #0 from Bank 0
CPU sends address #2 to Bank 2 and receives data #1 from Bank 1
CPU sends address #3 to Bank 3 and receives data #2 from Bank 2
CPU receives data #3 from Bank 3
As a result, the data from all four requests will arrive consecutively from the SDRAM without any delay in between. But if interleaving was not enabled, the same 4-address transaction would be roughly like this :-

SDRAM refreshes
CPU sends address #0 to SDRAM
CPU receives data #0 from SDRAM
SDRAM refreshes
CPU sends address #1 to SDRAM
CPU receives data #1 from SDRAM
SDRAM refreshes
CPU sends address #2 to SDRAM
CPU receives data #2 from SDRAM
SDRAM refreshes
CPU sends address #3 to SDRAM
CPU receives data #3 from SDRAM
As you can see, with interleaving, the first bank starts transferring data to the CPU in the same cycle that the second bank receives an address from the CPU. Without interleaving, the CPU would send the address to the SDRAM, receive the data requested and then wait for the SDRAM to refresh before initiating the second data transaction. That wastes a lot of clock cycles. That's why the SDRAM's bandwidth increases with interleaving enabled.

However, bank interleaving only works if the addresses requested consecutively are not in the same bank. If they are, then the data transactions behave as if the banks were not interleaved. The CPU will have to wait till the first data transaction clears and that SDRAM bank refreshes before it can send another address to that bank.

Each SDRAM DIMM consists of either 2 banks or 4 banks. 2-bank SDRAM DIMMs use 16Mbit SDRAM chips and are usually 32MB or less in size. 4-bank SDRAM DIMMs, on the other hand, usually use 64Mbit SDRAM chips though the SDRAM density may be up to 256Mbit per chip. All SDRAM DIMMs of at least 64MB in size or greater are 4-banked in nature.

If you are using a single 2-bank SDRAM DIMM, set this feature to 2-Bank. But if you are using two 2-bank SDRAM DIMMs, you can use the 4-Bank option as well. With 4-bank SDRAM DIMMs, you can use either interleave options.

Naturally, 4-bank interleave is better than 2-bank interleave so if possible, set it to 4-Bank. Use 2-Bank only if you are using a single 2-bank SDRAM DIMM. Note, however, that Award (now part of Phoenix Technologies) recommends that SDRAM bank interleaving be disabled if 16Mbit SDRAM DIMMs are used. This is because early 16Mbit SDRAM DIMMs used to have stability problems with bank interleaving. All SDRAM modules can now use bank interleaving without stability problems.


SDRAM Precharge Control
Options : Enabled, Disabled

This feature is also labelled as SDRAM Page Closing Policy in some BIOSes. This feature determines whether the processor or the SDRAM itself controls the precharging of the SDRAM. If this option is disabled, all CPU cycles to the SDRAM will result in an All Banks Precharge Command on the SDRAM interface which improves stability but reduces performance.

If this feature is enabled, precharging is left to the SDRAM itself. This reduces the number of times the SDRAM is precharged since multiple CPU cycles to the SDRAM can occur before the SDRAM needs to be refreshed. So, enable it for optimal performance unless you are facing system stability issues with this option enabled.



DRAM Data Integrity Mode

Options : ECC, Non-ECC

This BIOS setting is used to configure your RAM's data integrity mode. ECC stands for Error Checking and Correction and it should only be used if you are using special 72-bit ECC RAM. This will enable the system to detect and correct single-bit errors. It will also detect double-bit errors though it will not correct them. This provides increased data integrity and system stability at the expense of a little speed.

If you own ECC RAM, enable it (set ECC) to benefit from the increased data integrity. After all, you have already spent so much for the expensive ECC RAM so why not use it? ;)  If you are not using ECC RAM, choose Non-ECC instead.





if you know you don't know, the way could be more easy ...
June 24, 2002 1:00:52 PM

wow, thanks, that pretty much answers all my questions, it's too bad my system won't run stable at the most agressive timings though, i'm getting an rma on my corsair ram and trying to exchange it for some samsung with newegg, there's no reason pc3000 ram rated for 185 mhz shouldn't be running agressivley at 166 mhz, what a damn shame.
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Anonymous
a b à CPUs
a b } Memory
June 24, 2002 2:05:41 PM

at worst, it was been a faulty overclocking product.
whatsoever i am astonishing about your issue.

sometimes the overclocking miscarries from some sticks but normally Corsair has validated its overclocking of 185Mhz. you said you didn't succeed at 166Mhz, that is to say 19Mhz under the specs. weird?!?

moreover i am wondering about the type of your Corsair memory?

furthermore be careful when you modify the timing settings of your memory. some memory might not appreciate all the modifications.


if you know you don't know, the way could be more easy ...
June 25, 2002 12:39:58 AM

Greetings Mr kalliman. I Have the exact same motherboard with the PC3200 corsair ram.

for maximum performance, first Flash the bios to the latest revision, 2619 i think.
then put the ram to turbo. (this changes most of the settings to their fastest and tweaks certain things you cannt manually change)

then manually check the settings so that:
cycle length = 2
bank interleave = 4
trp = 2
tras = 2
trcd = 5
burst length = 8
que depth = 4
drive strength = auto
command rate = 1
i/o timing = auto
fast r/w = enabled
and
cont. dram = enabled.

also, bear in mind that these are VERY aggressive memory timings.
with my corsair PC3200 @ 166mhz i found that these memory timings made my ram ever so slightly unstable. a small Vdimm boost to 2.60v was required for rock solid stability.
to test your ram stability, i suggest MEMTEST86.

cheers. enjoy



<font color=blue>All religions are true, for a given value of 'true' - Terry Pratchett.</font color=blue>
June 25, 2002 6:35:01 AM

already tried all of that, turbo settings cause the system to freeze as do setting everything manually and keeping it set to normal. This is simply unacceptable for a stick that i payed $195 for. It's rated to run at cas 2 at 185 mhz, and it can't even do it at 166, unacceptable. I should have gone with the recommendations and reviews pointing towards the samsung chips, if only newegg had them in stock, well now they do and they approved my RMA request and i'll be ordering a samsung dimm from them within the next few days. I just don't feel like having an RMA battle with corsair, now i know why they have their help forums, because none of their dimms work as indicated.
June 25, 2002 6:44:09 AM

Correction... its certified for Cas2,2,2... the sheer number of memory timing variables available mean that its running considerably harder than what they test at, even at a lower speed.

i assume you tried raising the voltage yes?


<font color=green>Proud member of THG's</font color=green> <font color=blue>Den Of Thieves</font color=blue> :lol: 
Anonymous
a b à CPUs
a b } Memory
June 25, 2002 8:31:15 AM

but what are the meanings of all those memory parameters?


<i>if you know you don't know, the way could be more easy ...</i>
Anonymous
a b à CPUs
a b } Memory
June 25, 2002 8:41:19 AM

can you explain why this trying with Corsiar?






<i>i am wondering if there is some van truth thrut...</i>


<i>if you know you don't know, the way could be more easy ...</i>
June 25, 2002 1:27:30 PM

actually, i was browing through the corsair forums and someone had the same problem that i did, same mobo same dimm, and when the guy set it to turbo it didn't work, a guy from corsair resonded and said it's not guaranteed to work on turbo, and that you have to manually set the timings and it should definitely work at 2-2-2-5 1T becasue that's what they test it at on that mobo, but guess what, i did just that and it still did not work. I'm not about to raise the voltage to give the dimm some help, it should be able to do it at the voltage it's running at now, and i'm willing to bet anything that the samsung stick will be able to do it.........either way, $195 is way too much for this dissapointing performance, plus i'm not about to unlock my multiplier so i won't be running it at 185 mhz even if it really can do that, which hi highly doubt.
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