Memory timings for A7V133

[dmcmahon]

I've got CAS2 latency SDRAM, but I'm pretty sure the mobo is not using the extra speed, 'cause in the BIOS setup program with the speed in "Auto" mode (the default), it shows "3T" for the CAS number, as well as a bunch of other settings e.g. "RAS to CAS" etc. Does anyone know what all these numbers mean and how to set them for better performance? For example, can I go to manual and change the "3T" to a "2T" for my CAS2 DRAM? What the heck do I do with all the other numbers, though?

P.S. there is another RAM-related parameter, something that sounds like byte-combining, this seems to be "Disabled" by default. Why? The description makes it sound like it could help, and the description doesn't mention what the downside is.

 

[HellDiver]

<b>dmcmahon :</b>

Me and 2 friends of mine ordered 3 256MB 133MHz CAS2 sticks from Crucial (Micron) about a month ago. Got 'em, installed. I got Asus P3V4X (I was just upgrading the memory, they bought new boxes), they have brand new Asus A7V133 boards.

On the next boot after replacing my 256MB CAS3 with Crucials CAS2 stick, <b> my BIOS</b> correctly identified memory (through SPD) as CAS 2 memory and adjusted settings aggordingly. After plugging the stick in one of my friends rigs and booting, BIOS came up with CAS of 3 for an identical stick of memory in the auto mode. (Hint : I think that either Asus has a crappy BIOS code, or KT133A may be screwed altogehter, VIA always had problems with memory)

After manually setting the timings to 2-2-2 (CAS, RAS Precharge Delay, RAS to CAS) the rig booted just fine.

BTW, <b>NOTE:</b> My friends received A7V133 Rev 1.05, with a manual Rev 1.02, and there were things clearly different in the manual from what we encountered in the BIOS and on the board silkscreening. IIRC, Promise controller mode jumper settings, for example!

 

[dmcmahon]

Thanks, man. So 2-2-2 for all numbers. Unfortunately the mo_bo reports my ram as CAS2, either it's a bug or I got ripped off. I have BIOS 1004. Question: if I try this and it doesn't work, will I screw the system or will it come back up in a safe mode? Seems like the safe mode works for CPU and memory frequencies but doesn't say about latencies. Thanks...

 

[HellDiver]

<i>Unfortunately the mo_bo reports my ram as CAS2</i>
I think you ment to say CAS3. CAS2 is as good as it gets today. You can check whether you were ripped off by reading the sticker on the memory stick, or if none present, by reading chips models and visiting manufacturer's site for their specs.

You will not screw your system if you mannually force CAS3 into CAS2 timings, at worst your system won't boot up, or show severe instability if it does. You can always reboot and change it back.

 

[phsstpok]

Get a copy of CTSPD (sorry no link). It will report the information stored in the SPD EEPROM on any DIMM.

 

[dmcmahon]

CTSPD doesn't detect any DIMMS at all on my machine.

 

[dmcmahon]

Yeah, I meant CAS3. You say the worst that can happen is my machine won't boot, but like, if that happens, then how will I ever get back into the BIOS to change back? You see my dilemma? I know for sure if you mis-set the freqs, the A7V133 will come back in 100 MHz mode. Docs don't say what happens if you mis-set the CAS timings. Aaak!

 

[Tempus]

I wouldn't worry about it not working. Almost all brands of RAM at CAS3 can be set to CAS2 with no problems. Plus you say yours really is CAS2, so you should do it. HINT: Just set the first setting to "7ns143MHz" in the BIOs, and it will set up all of the timings correctly for CAS2 automatically.

- I don't write Tom's Hardware Guide, I just preach it"

 

[phsstpok]

That's strange. No data at all or just no manufacturer name?

 

[ejsmith2]

Can you set it for CAS -.5? Or is that to be release in revision 6?

 

[HellDiver]

<i>You say the worst that can happen is my <b>machine</b> won't boot</i>
I actually said <b>"system"</b> not "machine". By "system" I meant <i>"operating system"</i>, because booting and OS requires some memory usage, and if the memory is improperly configured (i.e. timings too short), somewhere throughout the windows boot screens it may stuck. My apologies for not being overly clear on that one. As I said, at worst you'll have to reboot. Nothing to be afraid of here.

 

[dmcmahon]

Hey, thanks. I didn't get the distinction. I guess I figured even the BIOS needs some RAM (to run that character-mode app that lets you change stuff), and I wasn't sure what it would do if it couldn't get any RAM because the CAS settings were wrong. Hmmm, I wonder, would the BIOS come up if there were no ram in the system?