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Setting the same timing for RAMs with different timings?

Last response: in Memory
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February 26, 2011 9:23:55 PM

Hi!

I had 2x1 GB of Kingmax 800 MHz (PC-6400) RAMs.
Recently I've upgraded my system with an additional 2x1 GB of also Kingmax 800 MHz (PC-6400) RAMs:

So now my system looks like this:

RAM Slot 1 and 2:
old 1 GB DDR2 Kingmax 800 MHz RAMs with timings:
3-3-3-9-12 200 MHz
4-4-4-12-16 266 MHz
5-5-5-18-23 400 MHz

RAM Slot 3 and 4
new 1 GB DDR2 Kingmax 800 MHz RAMs which unfortunately have different timings:
4-4-4-12-16 266 MHz
5-5-5-15-20 333 MHz !!!
6-6-6-18-24 400 MHz

When I let the BIOS select the timings automatically, it choosed 5-5-5-15 and 334 MHz (CPU-z).

I wanted to get back the 400 MHz, which I had, when I had 2 GB of RAM
so in BIOS, below 1st information: 5-5-5-15-3-44-5-3 I set

DRAM Frequency to 800 MHz and timings
CAS# Latency
DRAM RAS# to CAS# Delay
DRAM RAS# Precharge
DRAM RAS# Activate to Precharge
to 5-5-5-15 manually but there is no field for the 5th value, there is only a
RAS# to RAS# Delay field with values from 5 to 15 which would not be proper. So I left it Auto.

(There are these fields also, which I left Auto:
DRAM CLK Skew on Channel A1
DRAM CLK Skew on Channel A2
DRAM CLK Skew on Channel B1
DRAM CLK Skew on Channel B2

2nd Information: 8-3-5-4-6-4-7
Read to Write Delay (S/D)
Write to Read Delay (S)
Write to Read Delay (D)
Read to Read Delay (S)
Read to Read Delay (D)
Write to Write Delay (S)
Write to Write Delay (D)

3rd Information: 13-5-1-6-6
Write to PRE Delay
Read to PRE Delay
PRE to PRE Delay
All PRE to ACT Delay
All PRE to REF Delay)

So now my problem is that when I look into CPU-z, it shows:
DDR2 4096 MBytes
Dual Channel Symmetric DC Mode
DRAM Frequency 400,9 MHz
FSB: DRAM 2:3
Command Rate (CR) 2T
5-5-5-15 (CL, tRCD, tRP, tRAS) but
the 5th value (Row Refresh Cycle Time - tRFC) is 44 clocks. :??: 

Somebody please tell me, what is this 5th (Row Refresh Cycle Time - tRFC) value which is 44 at this moment, why is it so high (it should be near 20 or 23!!), and how can I manage to set it to 20 or 23?

My second concern is the following:
should I set DRAM Frequency to 800 MHz and 5-5-5-15 or 5-5-5-18 for timings or rather 6-6-6-18 because the previous timings are too high for my new RAMs?

/At this moment everything is working fine with 800MHz and 5-5-5-15-44, my system is stable./

Thank you everybody in advance!
a b } Memory
February 26, 2011 10:26:18 PM

With a lot of motherboards, when you use all four DIMM slots, you have to use the slowest of the timings as well as go to 2T command rate.
February 27, 2011 5:20:48 AM

Someone else please, a little more in details?
!