Adding memory with different speed and latency

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My current system (Core-2 Duo E6600 @ 2.4Ghz) has 1GB of memory using
two 512MB modules of DDR2 667Mhz Ram  with 5-5-5-15 timings.

I'm thinking about adding an additional 1GB or memory using DDR2 533Mhz
RAM with 3-3-3-8 timings.

My understanding is that if I add the 533Mhz RAM,  then all 2GB of
memory will run at the speed of the slowest RAM in the system which, in
this case, would be, the 533Mhz RAM.  But since the 533Mhz will have
faster latency/clock settings, I'm wondering how this would work.

Thanks to anyone who can clarify this.


Re: Adding memory with different speed and latency

BobKK47 wrote:
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The BIOS will selecting the slowest timing that makes both sets of
matched sticks work. Speedwise, it'll run at DDR2-533. The timings
will be adjusted to be consistent with that speed. The 5-5-5-15
memory will control the final timings used, as the 3-3-3-8 won't be
the timing limiter. So the timings the BIOS uses will definitely not
be 3-3-3-8, but something higher (slower).


Re: Adding memory with different speed and latency

On Wed, 10 Jan 2007 15:09:45 -0500 Too Much Ying and you will Pay With

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Unfortunately when it comes to memory changes the BIOS,"Auto Detect"
doesn't  always get it right because of the incorrectly hardware coded
bios chip on the ram(SMD).

Case in point new build for myself.

Two different brands on PC3200 512 meg of ram.Both labeled as cas 2.5
DDR 200/400 Mhz.

With auto-detect in the BIOS system will not boot with both sticks
in.Will boot with either in separately at 2.5/200X2.
This is in either single mode or dual interleave when both sticks in.

Got system working in both single and dual interleave(AMD system) by
manually setting speed to 166 and cas 3 when both sticks in.Now I've
lost the 200 Mhz speed and the cas 2.5 but because they are now
working at 1gig in dual interleave mode this is way faster than none
DI mode so I can live with that and the fact I have a full 1 gig of
ram running in Dual Interleave.Would be nice to have them both running
at 2.5/200/400 but what they hey,the sticks were cheap :)

Note:With each successive RAM boot failure I/you have to clear the
CMOS with the power isolated from the system because when it comes to
ram the CMOS stores corrupt/incorrect data that can only be cleared
this way as there's a charge left in the CMOS if there's power to the
mother board and you have to re-enter the settings in the BIOS

Now this is for this board but I've had to do this when fitting
mis-matched ram on many boards.

If at all possible use matched ram from the same maker(Even that is
not 100% guaranteed).This doesn't confuse the BIOS so much.

If this luxury is not available see above.


My old Computer/Electronics tutor,"Bob Smith" said it all.

Computers and Electronics are not an,"Exact Science"

and neither is science ;-)

Free Windows/PC help,

Re: Adding memory with different speed and latency

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Its an spd, not a bios chip on the memory module.

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