845 Ultra ARU CPU FSB Ratios?

Question

The bios provides DRAM Frequencies of 200, 266 and Auto.  Given a FSB of 100, that means the ratio of CPU:FSB is 1:1 and 3:4.  (What is 'Auto')
If I run the FSB at 133, are these ratios preserved, or does some other ratio come into effect.  If I choose FSB of 133 and DRAM Frequency of 266, will I be running at 354 DDR?  If so, do you think a stick of Corsair PC2700 (333 DDR) will O/C to that level?

Answer 1

Quote
Originally posted by jdurg
If I recall correctly, once you reach a front-side-bus of 123 MHz, the ratio sticks at 1:1.  So at a fsb higher than 123, the memory ratio will ALWAYS be 1:1 no matter what you set it at.   X( You are correct on your ratio assumptions, but at 123 MHz the memory ratios become useless.  The Auto option is as it suggests.  The BIOS will automatically set all the RAM timings per what the chips are rated at.  So if you have the memory set to Auto, you won't be able to change the CAS timings and the other various memory options.
The lack of memory ratios on this particular board is what really hurts it.  I've got my 1.8A P4 overclocked to 2.52 GHz on a 140 MHz fsb.  However, the CPU is being choked to death by a memory bandwidth of only 2.0 GB/s.  If there were more memory ratios than the one 1:1 ratio that MSI gives us, I'm sure I could improve my system's performance quite a bit.  The other problem with the MSI board, that affects me at least, is that the temperature sensor seems to be out of whack.  PC Alert III and MBM5 say that my CPU is at 67-68 degrees Celsius under a full load.  With the case open and my hand right on the heatsink during that full load, I can tell you that the reported temperature is at least ten degrees off.  If it were really 68C, I would not be able to keep my hand on it without it feeling really warm.
So those are the only two things about the 845 Ultra-ARU that make me really wish I had gotten a different motherboard.   :(
Hi jdurg.
I just found a post on Usenet that was very interesting.  The poster has an 845 Ultra ARU.  Here's the quote:
All this time I used fuzzylogic 4 to overclock my 1.6a to 2.1 @ 133. now I
actually went into BIOS and adjusted my memory settings. This is what I did:
Changed....
DDR Frequency:    from 266 to AUTO
Configure DRAM Timing by:    from MANUAL to SPD
What I noticed was the CAS# LATENCY changed from 2.5 to 2 (I didn't adjust)
Now I use a program called CPU-Z to get information on the CPU, MB, and MEM.
speeds. Before the changes on the motherboard/CPU speed was normal like:
Before: (with out bios changes)
CPU Frequency: 2119.1 MHz
Clock Multiplier: x 16.0
FSB Frequency: 132.4 MHz
MEM Frequency: 351.4 MHz
before I had problems of computer freezing after a few hours.
Now: (after bios changes)
CPU Frequency: 2119.1 MHz
Clock Multiplier: x 16.0
FSB Frequency: 132.4 MHz
MEM Frequency: 264.9 MHz
also CAS# L: 2clocks, RAS# to CAS# Delay: 2clocks, RAS# Precharge: 2clocks
and Cycle time: 5clocks.
now my main question is how come the MEM Freq. has changed/decreased?
and my system is very stable now (no crashes). is this normal? I have a
no-name, cheap(only paid $60 can.) is this normal for this mem chips?
There was no reply to the message, but it looks like he was getting a 3:4 memory speed ratio with the FSB at 133.  This is good!  He had DRAM Frequency set to 266 and memory timings set to Manual.  Using AUTO and SPD brought his memory back to a 1:1 ratio.  My board won't be in until the end of the week... is there anyway you could verify this on your board?