Why can't I mix DDR333 with DDR400?

[Guest]

My old computer running XP SP2 had a DDR333 memory module (256MB) installed.
I purchased a new 512MB memory module yesterday (DDR333 isn't available any more).
The new memory module has a frequency of 400MHz.
I thought if I use both the modules together, the 400MHz module would downclock itself to 333MHz and the system would work fine. However, this isn't the case. If I start the computer with the 333MHz module, it boots up fine. If I start the computer with the 400MHz module, it boots up fine again. But then if I start the computer with both the memory modules installed, it completes POST fine, but windows won't boot, the system "hangs" on the windows XP boot screen. What's up?

 

[Unolocogringo]

Incompatable memory.
Install one stick.
Download CPUZ. install and run it.
Ckeck the SPD tab for memory timings.
Remove first stick and replace with second stick.
Boot up and run CPUZ again. Ckeck the SPD tab.
On the SPD tab you will find JEDEC specs for each module. Write these down for both sticks.

Is there a common setting for both sticks?
If so ,reboot and go into bios and manually set timings and voltages specified on the SPD tab.
Save and exit.
Let it reboot to windows. to ckeck settings.
Shut down and install second stick in different colored memory slot. Color matched pairs are for running dual channel matched sticks.
Boot computer. Hopefully you found a set of timings that work for both sticks.
If you can post the CPUID SPD tab setting we might be able to find a working set of timings.

 

[geekapproved]

Why would you even buy a 512mb stick??

I mean you could have bought a 1 or 2gb stick and sold (or tossed) the 256mb stick because it's pretty much useless anyways.

 

[Toxxyc]

What do you want to do with 768MB of RAM...? And at 333MHz? Yoh, time for an upgrayyd...

 

[mavroxur]

Rick_Criswell hit the nail on the head. You probably need to go into BIOS and force timings to the slower of the two sticks.

 

[Guest]

What do you want to do with 768MB of RAM...? And at 333MHz? Yoh, time for an upgrayyd...

Well, my requirements from a computer are pretty basic. I use this thing as an mp3 player, to check my emails, to surf the internet with google chrome, and that's about it.
I'm not a gamer and I use the mobo's integrated graphics (intel extreme graphics 2 with just 8 MB of shared memory), i dont need windows 7 or vista to check emails
I've managed to get both the memory modules to work together (760 MB total now), and overclocked the CPU
to 1.85GHz ( originally a P4@1.5GHz). I have comodo firewall and avira free running, task manager reports a total of 43 processes (peak commit charge 556700 k), and trust me, this computer is not at all slow at doing the things i want it to do

 

[Guest]

Incompatable memory.
Install one stick.
Download CPUZ. install and run it.
Ckeck the SPD tab for memory timings.
Remove first stick and replace with second stick.
Boot up and run CPUZ again. Ckeck the SPD tab.
On the SPD tab you will find JEDEC specs for each module. Write these down for both sticks.

Is there a common setting for both sticks?
If so ,reboot and go into bios and manually set timings and voltages specified on the SPD tab.
Save and exit.
Let it reboot to windows. to ckeck settings.
Shut down and install second stick in different colored memory slot. Color matched pairs are for running dual channel matched sticks.
Boot computer. Hopefully you found a set of timings that work for both sticks.
If you can post the CPUID SPD tab setting we might be able to find a working set of timings.

Rick, thanks, excellent answer
I got bot the memory modules working together
Went into BIOS, there's an option for "Top Performance", disabled it.
Next, went to "frequency/voltage control"
There's something in there with 3 options (2.0/ 2.66/ Auto) (sorry but i don't exactly remember what it's called, but if you'd like to know, please reply, i'd get into BIOS again and write the name of the option). It was set to "auto", I changed it to 2.0, restarted with both the modules installed, and it works !

Windows reports a total of 760 MB of RAM now, and i've been using this for about 3 hours, tried pretty much everything i do, and no freezes or crashes

I've installed CPU-Z,
Here's the info as it reads now :-

MEMORY TAB:
type: DDR
Size: 768 MB
timings:-
FSBRAM=4:3
CAS# LATENCY= 2.5 clocks
RAS# to CAS# delay (tRCD)=2 Clocks
RAS# Precharge (tRP)=2 Clocks
Cycle time (tRAS)=5 Clocks
DRAM Idle Timer=16 Clocks


SPD TAB:
SLOT 1: DDR
Module Size 256 MB
Max Bandwidth: PC3200 (200MHz)
JEDEC #1:
Frequency :200MHz
CAS# Latency: 2.5
RAS# to CAS#: 3
RAS# Precharge: 3
tRAS: 8
Voltage 2.50V
(No JEDEC #2 displayed for slot 1) {why??}

SLOT 2: DDR
Module Size: 512 MB
Max Bandwidth: PC2700 (166 MHz) {How come? I thought the 512 module was faster than the 256 module !}
JEDEC #1
Frequency :133
CAS# Latency:2
RAS# to CAS#:3
RAS# Precharge:3
tRAS:6
Voltage 2.50V

JEDEC #2
Frequency : 166
CAS# Latency:2.5
RAS# to CAS#:3
RAS# Precharge:3
tRAS:7
Voltage 2.50V

I'm not that good with memory timings, (I'm not an IT pro ), i think it's okay cause it's working okay.. But what do you think, is everything alright from these readings i posted?
And how come the 512 module says PC2700 and the 256 module says PC3200? I've seen the stickers on the memory modules, it's clearly written 333 in the 256 module, and 400 in the 512 module, but CPU-Z is reporting the 256 module to be faster? Please reply. And thanks again for pointing out the BIOS thingy, I can make the computer boot up to windows and everything seems to work after changing the BIOS options

 

[Guest]

Best answer selected by the_substitute_teacher.