A few questions regarding RAM

Hi all.

I'm currently looking into buying some new RAM for my Notebook (Core2
Duo at 133x(6-12) Mhz, Intel i945PM-Chipset). There are two
SO-DIMM-Slots, one of them currently holds a module of 1 GiB, 533Mhz
DDR2 RAM. The plan is to buy another module of the same size and speed,
and take advantage of the dual-channel capabilities of the chipset as
well as double the memory. I looked for information already, but there
are still a few quenstions I have:

1. It's unlikely that I will find a new module exaclty matching the
timings of the current one (4-4-4-11). How would this impact
dual-channel operation? Will I need / would it be very beneficial to use
two exactly matching modules?

2. How much impact do different timings have on speed, disregarding
dual-channel for now? For example, How much better would a module with
timings 4-4-4-5 perform in comparsion to one with 4-4-4-11 timings? Not
enough to care about I guess, but they print these values in the
catalog, so I'd like to know if I should look at them when deciding for
a brand.

3. How big is the actual benefit of using a dual-channel configuration?
I won't want to spend the money for two matching modules (if this is
necessary) just for 1% more performance... then I'd rather just buy one
new and keep the one I have already.

Thanks in advance for your answers.

Simeon

"Simeon Maxein" wrote in message
...
Hi all.

I'm currently looking into buying some new RAM for my Notebook (Core2
Duo at 133x(6-12) Mhz, Intel i945PM-Chipset). There are two
SO-DIMM-Slots, one of them currently holds a module of 1 GiB, 533Mhz
DDR2 RAM. The plan is to buy another module of the same size and speed,
and take advantage of the dual-channel capabilities of the chipset as
well as double the memory. I looked for information already, but there
are still a few quenstions I have:

1. It's unlikely that I will find a new module exaclty matching the
timings of the current one (4-4-4-11). How would this impact
dual-channel operation? Will I need / would it be very beneficial to use
two exactly matching modules?

2. How much impact do different timings have on speed, disregarding
dual-channel for now? For example, How much better would a module with
timings 4-4-4-5 perform in comparsion to one with 4-4-4-11 timings? Not
enough to care about I guess, but they print these values in the
catalog, so I'd like to know if I should look at them when deciding for
a brand.

3. How big is the actual benefit of using a dual-channel configuration?
I won't want to spend the money for two matching modules (if this is
necessary) just for 1% more performance... then I'd rather just buy one
new and keep the one I have already.

Thanks in advance for your answers.

Simeon

If you can't find a match,better to get two new matching modules.
You might be able to finagle the bios settings to run mismatched ram in dual
channel,but you also have to look out for single or double sided modules.I
made that mistake. They can have the same timings but won't run in dual
channel together and it's not easy to distinguish whjich is which when
buying online.

'Simeon Maxein' wrote:
| I'm currently looking into buying some new RAM for my Notebook (Core2
| Duo at 133x(6-12) Mhz, Intel i945PM-Chipset). There are two
| SO-DIMM-Slots, one of them currently holds a module of 1 GiB, 533Mhz
| DDR2 RAM. The plan is to buy another module of the same size and speed,
| and take advantage of the dual-channel capabilities of the chipset as
| well as double the memory. I looked for information already, but there
| are still a few quenstions I have:
|
| 1. It's unlikely that I will find a new module exaclty matching the
| timings of the current one (4-4-4-11). How would this impact
| dual-channel operation? Will I need / would it be very beneficial to use
| two exactly matching modules?
|
| 2. How much impact do different timings have on speed, disregarding
| dual-channel for now? For example, How much better would a module with
| timings 4-4-4-5 perform in comparsion to one with 4-4-4-11 timings? Not
| enough to care about I guess, but they print these values in the
| catalog, so I'd like to know if I should look at them when deciding for
| a brand.
|
| 3. How big is the actual benefit of using a dual-channel configuration?
| I won't want to spend the money for two matching modules (if this is
| necessary) just for 1% more performance... then I'd rather just buy one
| new and keep the one I have already.
_____

If you can't find a memory module with identical speed and latencies just
get a faster module (with lower latencies) of the same type (memory chip
count and registered, for example) and set the timings to the same values
for your old chip and new chip (a faster module with lower latencies can
always be set for a slower speed with longer latencies.) As long as the
these requirements are met, running dual channel should not be much of a
problem. Anyway, the gain of doubling the memory size to two GBytes will
improve the system performance much more than the difference between dual
channel and single channel DDR2 (depending on the application mix you run.

Phil Weldon


| Hi all.
|
| I'm currently looking into buying some new RAM for my Notebook (Core2
| Duo at 133x(6-12) Mhz, Intel i945PM-Chipset). There are two
| SO-DIMM-Slots, one of them currently holds a module of 1 GiB, 533Mhz
| DDR2 RAM. The plan is to buy another module of the same size and speed,
| and take advantage of the dual-channel capabilities of the chipset as
| well as double the memory. I looked for information already, but there
| are still a few quenstions I have:
|
| 1. It's unlikely that I will find a new module exaclty matching the
| timings of the current one (4-4-4-11). How would this impact
| dual-channel operation? Will I need / would it be very beneficial to use
| two exactly matching modules?
|
| 2. How much impact do different timings have on speed, disregarding
| dual-channel for now? For example, How much better would a module with
| timings 4-4-4-5 perform in comparsion to one with 4-4-4-11 timings? Not
| enough to care about I guess, but they print these values in the
| catalog, so I'd like to know if I should look at them when deciding for
| a brand.
|
| 3. How big is the actual benefit of using a dual-channel configuration?
| I won't want to spend the money for two matching modules (if this is
| necessary) just for 1% more performance... then I'd rather just buy one
| new and keep the one I have already.
|
| Thanks in advance for your answers.
|
| Simeon

Thanks for your answers so far.

If you can't find a memory module with identical speed and latencies just
get a faster module (with lower latencies) of the same type (memory chip
count and registered, for example) and set the timings to the same values
for your old chip and new chip (a faster module with lower latencies can
always be set for a slower speed with longer latencies.)

My BIOS does not offer any advanced settings like that I'm afraid, or I
didn't find the magic switch yet . Or is there some utility to change
these settings? I could try to just insert another module and look how
it is handled.

Simeon