memory upgrade (correction)

[Lanning]

The 490 manual states, "For optimal performance, fully buffered DIMMs (FBDs)
should be installed in *matched sets of four*. This enables quad-channel
operation and provides the highest memory bandwidth. Fully buffered DDR2
memory modules can also be installed in pairs of two; in this case, the
computer will continue to operate, but with a *slight reduction in
performance*."

Please comment on the *"slight reduction in performance"* that I should
expect when adding two 1GB modules rather than four 512MB modules to the
existing four 512MB modules.

I have already ordered two 1GB modules from Crucial, but I could return them
box unopened and spend $50 more to get four 512MB modules if it matters. Of
course, I should have read the manual and posted this question before
ordering the memory.

Thanks for any advice and information.

Roy

 

[Richard G. Harper]

As this is a limitation of your motherboard (not of Vista) you should
contact the system or motherboard manufacturer and ask them to elucidate.

 

[LVTravel]

The 490 manual states, "For optimal performance, fully buffered DIMMs
(FBDs) should be installed in *matched sets of four*. This enables
quad-channel operation and provides the highest memory bandwidth. Fully
buffered DDR2 memory modules can also be installed in pairs of two; in
this case, the computer will continue to operate, but with a *slight
reduction in performance*."

Please comment on the *"slight reduction in performance"* that I should
expect when adding two 1GB modules rather than four 512MB modules to the
existing four 512MB modules.

I have already ordered two 1GB modules from Crucial, but I could return
them box unopened and spend $50 more to get four 512MB modules if it
matters. Of course, I should have read the manual and posted this question
before ordering the memory.

Thanks for any advice and information.

Roy

So, you are upgrading from 2 GB of memory to 4 GB. Does your computer have
4 open memory slots? Unless you do, you would need 4 1 GB modules and
remove the 4 512 MB modules you now have installed.

If this is the Dell Presicion 490 board I would recommend that you purchase
4 1 GB cards which should run you about 159.96 which is only $30 more than 4
512 MB modules.


http://www.crucial.com/store/listparts.aspx?model=Precision WorkStation 490
Part Description Price ea. Qty
Total
CT675884 1GB, 240-pin DIMM $ 39.99 X 4 $ 159.96

This way, if you decided to increase to 8 GB or larger later for 64 bit OS,
you would remove the 4 512 modules you now have and upgrade them to 1 or 2
GB cards. That motherboard apparently can handle 8 4GB memory cards for 32
GB of RAM.

 

[Curious]

Why technically would 4 1GB units work any better then 2 2 GB units
especially since they more draw more power from the PSU and they are DDR2
units?

 

[Lanning]

The 490 manual states, "For optimal performance, fully buffered DIMMs
(FBDs) should be installed in matched sets of four. This enables
quad-channel operation and provides the highest memory bandwidth."

 

[Lanning]

You make a great point! Thank you very much. If I stick to the manual's
recommendation of set(s) of four matched modules, then I should put a new
set of four matched 1GB (rather than 512MB) sticks in the front set of four
slots.

Would there then be any issue if I also put the current four matched 512MB
sticks in the back set of four slots?

As you surmise, the manual says, "This computer supports a maximum of 32 GB
of memory when eight 4-GB DIMMs are installed."

 

[LVTravel]

You make a great point! Thank you very much. If I stick to the manual's
recommendation of set(s) of four matched modules, then I should put a new
set of four matched 1GB (rather than 512MB) sticks in the front set of
four
slots.

Would there then be any issue if I also put the current four matched 512MB
sticks in the back set of four slots?

As you surmise, the manual says, "This computer supports a maximum of 32
GB
of memory when eight 4-GB DIMMs are installed."

You should have no issues anyway but I would recommend that you move the 4
512MB sticks to the currently vacant slots and putting the 4 1GB sticks in
the original slots. It shouldn't really matter for speed if you just put
the new chips in the vacant slots but some computers just seem to run better
with the larger chips in the bank 0 slots (or at least that is the way it
used to be and of course that is IMHO.)

 

[Lanning]

I'm sorry, that isn't the answer in depth. It wasn't me you asked, anyway,
sorry again.

 

[Lanning]

You should have no issues anyway but I would recommend that you move the 4
512MB sticks to the currently vacant slots and putting the 4 1GB sticks in
the original slots. It shouldn't really matter for speed if you just put
the new chips in the vacant slots but some computers just seem to run
better with the larger chips in the bank 0 slots (or at least that is the
way it used to be and of course that is IMHO.)

OK, thanks. Still, though, I wonder what the "slight reduction" in
performance amounts to if I leave the four original 512MB modules in their
original place (the four slots of the first set of four slots) and the two
new 1GB modules in the first two slots of the second set of four slots.

Addressing that is the nice post below that I got from the Dell forum.
---------------------------------------------------------------------------------
It depends entirely on whether the programs you run are memory-intensive or
not.
While this article applies to dual channel, quad-channel is basically the
same deal (4 channels in parallel instead of 2). But as the benchmark links
point out, multi-channel memory doesn't necessarily mean your Precision as a
whole will perform noticeably faster - memory read/write speed is only a
small part of the total performance equation:

http://en.wikipedia.org/wiki/Dual-channel_architecture

The only benchmark results I've found specific to quad-channel were
comparing dual-channel to quad-channel on a Mac (!), but the results are
interesting just the same:

http://www.anandtech.com/showdoc.aspx?i=2816&p=12

So in general, the performance hit running at full bore is anywhere from 0
to 15% for single to dual channel, and about the same again for dual to
quad. Is it worth $50? I dunno.

------------------------------------------------------------------------------------------

 

[Lanning]

You should have no issues anyway but I would recommend that you move the 4
512MB sticks to the currently vacant slots and putting the 4 1GB sticks in
the original slots. It shouldn't really matter for speed if you just put
the new chips in the vacant slots but some computers just seem to run
better with the larger chips in the bank 0 slots (or at least that is the
way it used to be and of course that is IMHO.)

I put the two 1GB sticks in the first two slots of the second set of four
slots. It's all dual-channel, now. Says so in CMOS. I'll live with it.

Here's something someone quoted about *equal capacity* that I believe:

"Additional non-shipping (but valid) configurations can be made by
installing matched pairs of DIMMs in slots DIMM1/DIMM2, DIMM3/DIMM4,
DIMM5/DIMM6, and DIMM7/DIMM8. These will result in dual channel operation
which is lower bandwidth that quad-channel (where DIMM1/2/3/4 and
DIMM5/6/7/8 are required to match for full quad-channel). We do not ship
these configurations, but they are valid and no error message will be
displayed."

-----------------------------------------------------------------------------

MSINFO32.EXE now reports memory as (in Vista Business SP1):

installed was 2.00 GB, now 4.00

total physical was 2.00 GB, now 3.25

available physical was 879 MB, now 2.36 GB

total virtual was 4.23 GB, now 6.71

available virtual was 2.69 GB, now 5.79

page file was 2.29 GB, now 3.54

 

[LVTravel]

I put the two 1GB sticks in the first two slots of the second set of four
slots. It's all dual-channel, now. Says so in CMOS. I'll live with it.

Here's something someone quoted about *equal capacity* that I believe:

"Additional non-shipping (but valid) configurations can be made by
installing matched pairs of DIMMs in slots DIMM1/DIMM2, DIMM3/DIMM4,
DIMM5/DIMM6, and DIMM7/DIMM8. These will result in dual channel operation
which is lower bandwidth that quad-channel (where DIMM1/2/3/4 and
DIMM5/6/7/8 are required to match for full quad-channel). We do not ship
these configurations, but they are valid and no error message will be
displayed."

-----------------------------------------------------------------------------

MSINFO32.EXE now reports memory as (in Vista Business SP1):

installed was 2.00 GB, now 4.00

total physical was 2.00 GB, now 3.25

available physical was 879 MB, now 2.36 GB

total virtual was 4.23 GB, now 6.71

available virtual was 2.69 GB, now 5.79

page file was 2.29 GB, now 3.54

The only reason I was trying to get you to go with the 4 1GB chips instead
of just two was the issue with chip matching. I at that time didn't realize
that you were using a 32 bit operating system (OS.) If you later purchase 2
1GB chips, even from the same manufacturer, they may not match and therefore
won't work correctly. It does look like you are only using a 32 bit OS so
the additional memory right now would not have been helpful. Only if you
went to the 64 bit version of the OS.

 

[Lanning]

The only reason I was trying to get you to go with the 4 1GB chips instead
of just two was the issue with chip matching. I at that time didn't
realize that you were using a 32 bit operating system (OS.) If you later
purchase 2 1GB chips, even from the same manufacturer, they may not match
and therefore won't work correctly. It does look like you are only using
a 32 bit OS so the additional memory right now would not have been
helpful. Only if you went to the 64 bit version of the OS.

Thank you, I got a lot of understanding from your help. So, at the bottom
line, I am satisfied that I spent $80 less frivously than I might have spent
$160. Now, I will proceed to stop wondering about the "slight reduction" in
performance in dropping from quad to dual channel. At least I got the dust
out of the machine, and I took the OS offer to stop off in CMOS where I
changed the LPT port from PS/2 to ECP and enabled DMA for it.