DDR memory settings?

[Joe Pfeiffer]

Recently got a new Averatec 7100-series laptope, and upgraded it by
adding some memory. Averatec specifies PC2700 (333 MHz) DDR memory,
which is what I got.

First thing after a memory install is, of course, to run memtest86+ on
it... and memtest86+ is reporting 100 MHz (DDR200) memory with
timings of 2.5-2-2-5. Went to the BIOS to adjust it, and found no
memory settings in the BIOS.

So... what's going on? First, is DDR memory smart enough to report
its speed? Does memtest86+ report memory speeds accurately? Should
there be something in the control panel or a downloadable utility (I
don't normally run Windows) to adjust memory speeds? What should I be
asking that I don't know enough to ask?

Thanks,

 

[David Wang]

Recently got a new Averatec 7100-series laptope, and upgraded it by
adding some memory. Averatec specifies PC2700 (333 MHz) DDR memory,
which is what I got.

First thing after a memory install is, of course, to run memtest86+ on
it... and memtest86+ is reporting 100 MHz (DDR200) memory with
timings of 2.5-2-2-5. Went to the BIOS to adjust it, and found no
memory settings in the BIOS.

So... what's going on? First, is DDR memory smart enough to report
its speed? Does memtest86+ report memory speeds accurately? Should
there be something in the control panel or a downloadable utility (I
don't normally run Windows) to adjust memory speeds? What should I be
asking that I don't know enough to ask?

There's nothing to adjust. Upon powerup, part of the init sequence
is for the memory controller to quiery the memory module what the
appropriate configuration parameters are. The configuration parameters
include capacity, organization, speed and what not. There's a little
eprom on each memory module that contains this information, and the
memory controller configures itself appropriately by reading this
eprom.

On some dekstops, in particular those targetted toward
hardware enthusiasts (hackers), there are settings that will let you
override certain values that the memory module returns. i.e. the
memory module can identify itself as a CAS2 memory, but you can over
ride that and set the CAS latency to 3 (or vice versa).

In the case of your laptop, the focus is on ease of use and lower
power profile. The memory system is sometimes downclocked on purpose
to save power. So my guess is that you have a DDR-200 memory system with
to way to adjust anything.

 

[Joe Pfeiffer]

In the case of your laptop, the focus is on ease of use and lower
power profile. The memory system is sometimes downclocked on purpose
to save power. So my guess is that you have a DDR-200 memory system with
to way to adjust anything.

Found the answer (in AMD's BIOS writer's guide...). It turns out
that, depending on the configuration of the chips on the SO-DIMMs, the
CPU can decide that loading considerations mean it can't run at the
memory's rated speed. So it'll slow down the memory interface.

In this case, one of the memories is DDR400 and the other is DDR333
(and memtest86+ reports them as running at those speeds), but with
both in there together it slows down to DDR200.

 

[George Macdonald]

Recently got a new Averatec 7100-series laptope, and upgraded it by
adding some memory. Averatec specifies PC2700 (333 MHz) DDR memory,
which is what I got.

First thing after a memory install is, of course, to run memtest86+ on
it... and memtest86+ is reporting 100 MHz (DDR200) memory with
timings of 2.5-2-2-5. Went to the BIOS to adjust it, and found no
memory settings in the BIOS.

What does it report for the "base" memory speed without the upgrade? Are
you sure it's set in BIOS Setup to run on "Max Performance" for A/C
operation?... i.e. not off the battery "Max Power Savings" settings.

So... what's going on? First, is DDR memory smart enough to report
its speed? Does memtest86+ report memory speeds accurately? Should
there be something in the control panel or a downloadable utility (I
don't normally run Windows) to adjust memory speeds? What should I be
asking that I don't know enough to ask?

Yep - all PC DIMMs have a SPD (Serial Presence detect) EPROM with the
appropriate timings programmed on it. On POST the BIOS queries it/them and
sets the global memory timings based on values returned from the SPD. If
you have DIMMs with slightly different SPD values, the BIOS is supposed to
choose timings which work with the slowest DIMM in the system. It's been
known for a BIOS to get confused about sorting this out, so the first thing
to do would be to look for a BIOS upgrade.

Memtest86+ is usually pretty good about keeping up to date with new
chipsets so make sure you have a recent version. Does it report the
chipset correctly? If so, I've found it usually reports memory
speed/timings accurately.