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From: Stan Hoeppner on 16 Apr 2010 20:10
Camaleón put forth on 4/16/2010 8:31 AM:

> It can be worst, though. There are manufacturers that paint all the RAM
> slots in black or using the same color and so forcing us to read the
> manual >:-)

The manufacturers have bastardized the color coding to the point it's
useless; thus reading the manual is the only safe bet to get dual channel
operation setup correctly.

The mobo industry has taken the DIMM slot color coding concept and run it
through the Microsoft "embrace and extend" process, thus ruining
interoperability. ;)

--
Stan


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From: Nick Boyce on 17 Apr 2010 02:10
On 17/04/2010 01:03, Stan Hoeppner wrote:
> Camaleón put forth on 4/16/2010 8:31 AM:
>
>> It can be worst, though. There are manufacturers that paint all the RAM
>> slots in black or using the same color and so forcing us to read the
>> manual >:-)
>
> The manufacturers have bastardized the color coding to the point it's
> useless; thus reading the manual is the only safe bet to get dual channel
> operation setup correctly.

Um ... just my 2p: [score -1, redundant]

My current rig - Abit NF7-S V2 mobo (Nforce 2 chipset) and Athlon XP CPU
- has 3 DIMM slots all the same fetching shade of blue. I initially
added two 256Mb sticks in slots 1 & 2, and got dual channel operation
(the BIOS reports it at boot time : "Dual Channel Operation Enabled").
When I subsequently added another 512Mb stick in slot 3 this did not
apparently affect dual channel operation (the message still appears).
Maybe I get dual channel for the first 512Mb, but only single channel
for the second 512Mb.

I had to refer to the manual, *and* take advice from the wonderful
members of alt.comp.periphs.mainboard.abit. The latter assured me
adding the 3rd stick wouldn't prevent dual channel operation. Some day
I must try to find out what memory speed I actually get.

No more Abit now though, sigh.

Cheers
Nick
--
Q: Why can't scientists just make up their minds already?
A: Because if they did, they'd be theologians, not scientists.


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From: Stan Hoeppner on 17 Apr 2010 08:40
Nick Boyce put forth on 4/16/2010 11:35 PM:

> My current rig - Abit NF7-S V2 mobo (Nforce 2 chipset) and Athlon XP CPU
> - has 3 DIMM slots all the same fetching shade of blue. I initially
> added two 256Mb sticks in slots 1 & 2, and got dual channel operation
> (the BIOS reports it at boot time : "Dual Channel Operation Enabled").
> When I subsequently added another 512Mb stick in slot 3 this did not
> apparently affect dual channel operation (the message still appears).
> Maybe I get dual channel for the first 512Mb, but only single channel
> for the second 512Mb.

On all nForce2 boards DIMM1 is a channel and DIMM2 and DIMM3 are the other
channel. Why nVidia did this I can only guess. It is indeed a strange
design, very asymmetric. I'm guessing they intended a 4 slot design but ran
into impedance or drive quality issues during verification and had to drop
one socket to get the northbridge to run reliably. That's just a guess.
I'm also guessing most nForce2 owners put sticks in slot 1 and 2 and left
slot 3 empty. That's what I did, with two 256s and later two 512s. I have
the Biostar M7NCD Pro model.

> I had to refer to the manual, *and* take advice from the wonderful
> members of alt.comp.periphs.mainboard.abit. The latter assured me
> adding the 3rd stick wouldn't prevent dual channel operation. Some day
> I must try to find out what memory speed I actually get.

Populating slot 3 won't disable dual channel operation. What happens is you
don't get full bandwidth for memory addresses beyond [slot 1 capacity * 2]
when you stick more total memory in slots 2+3 than you have in slot 1, such
as 1GB in slot 1 and 2GB in slot 2+3, e.g. three 1GB DIMMS. The last gig of
address space exists in the second channel so bandwidth to it is limited to
single DIMM throughput.

It's almost irrelevant anyway on a socket A platform because the processor
bus is limited to 3.2GB/s unless overclocked. Each memory channel is
3.2GB/s if using DDR 400 for 6.4GB/s total in dual channel mode. AGP and
PCI devices are never going to be able to DMA 3.2GB/s while the CPU is at
full load because applications just aren't written in a way to enable such a
thing, even with heavy multitasking. Thus, any excess bandwidth over about
4GB/s won't be noticed. On systems using CPUs with integrated memory
controllers, such as most of the 64bit AMDs and the Intel Core I5/I7, dual
(triple) channel operation needs to be enabled. One will likely see
performance degradation if using a single DIMM on such machines if running
applications that actually take advantage of or stress the machines. If you
don't notice single channel performance degradation on one of these systems
then I'd say you bought too much machine for the intended use.

> No more Abit now though, sigh.

+1 Abit was awesome.

Luckily I acquired the Abit legend, the BP6. Still have it. And it's still
running after all these years. I have dual Celeron 366s in it running at
512MHz. Works great as a personal MX SMTP/IMAP/web/webmail/Samba/DNS
resolver running Lenny and a kernel.org kernel. I dropped in a SATA card
and a 500GB WD a while back to freshen it up a bit. The Abit mobo is over
10 years old now and provides more performance than the server really needs
for most things, idle most of the time. The only really taxing thing it
does is an occasional kernel build and imagemagick operations on photos
going on the website. I will admit it's a bit slow here. It runs 25
minutes for kernel builds with my config using CONCURRENCT_LEVEL=3.
(without concurrency it takes about 40-45 mins)

It's interesting that two platforms I've owned both came up in this thread,
nForce2 and Abit. Some planets must be aligned or something. :)

--
Stan


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From: Lisi on 17 Apr 2010 11:10
On Saturday 17 April 2010 05:35:45 Nick Boyce wrote:
> On 17/04/2010 01:03, Stan Hoeppner wrote:
> > Camaleón put forth on 4/16/2010 8:31 AM:
> >> It can be worst, though. There are manufacturers that paint all the RAM
> >> slots in black or using the same color and so forcing us to read the
> >> manual >:-)
> >
> > The manufacturers have bastardized the color coding to the point it's
> > useless; thus reading the manual is the only safe bet to get dual channel
> > operation setup correctly.
>
> Um ... just my 2p: [score -1, redundant]
>
> My current rig - Abit NF7-S V2 mobo (Nforce 2 chipset) and Athlon XP CPU
> - has 3 DIMM slots all the same fetching shade of blue. I initially
> added two 256Mb sticks in slots 1 & 2, and got dual channel operation
> (the BIOS reports it at boot time : "Dual Channel Operation Enabled").
> When I subsequently added another 512Mb stick in slot 3 this did not
> apparently affect dual channel operation (the message still appears).
> Maybe I get dual channel for the first 512Mb, but only single channel
> for the second 512Mb.

I too have an Abit NF7 (tho' not an -S). The memory was installed by the
shop where I bought the components of my computer. (I was intending to build
it myself and he didn't trust me with the CPU or memory!!) He told me taht I
had dual channel memory installed, and would need to replace both 256 Mb
sticks if I increased the memory capacity.

I have never seen any sign of dual channel operation. (Tho' I didn't know what
to look for, which hardly helped!)

dmidecode gives:

Memory Device
[snip]
Size: 256 MB
Form Factor: DIMM
Set: None
Locator: A0
Bank Locator: Bank0/1
[snip]

Memory Device
[snip]
Size: No Module Installed
Form Factor: DIMM
Set: None
Locator: A1
Bank Locator: Bank2/3
[snip]

Memory Device
[snip]
Size: 256 MB
Form Factor: DIMM
Set: None
Locator: A2
Bank Locator: Bank4/5

Would I be correct in taking this to mean that the memory modules appear to
be incorrectly installed, and that I could improve my memory performance by
moving one of the modules that dual channel functions? And also, if that
does not give me enough improvement (which it almost certainly won't), I
could add another module in the third channel, which would not necessarily
need to be the same size as the other two?

TIA
Lisi


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From: Stan Hoeppner on 17 Apr 2010 11:30
Lisi put forth on 4/17/2010 10:04 AM:

> Would I be correct in taking this to mean that the memory modules appear to
> be incorrectly installed, and that I could improve my memory performance by
> moving one of the modules that dual channel functions? And also, if that

No, they are currently properly installed for dual channel operation.

> does not give me enough improvement (which it almost certainly won't), I
> could add another module in the third channel, which would not necessarily
> need to be the same size as the other two?

There is no 3rd channel. There are 3 DIMM slots, but slots 2 and 3 are part
of the same channel. The nForce2 northbridge chip for some odd reason was
designed to support 1 DIMM on channel 0 and 2 DIMMs on channel 1.

As long as you have a DIMM installed in slot 1 and a DIMM installed in
either or both of slots 2 and 3, you are running in dual channel mode.

# of DIMM slots does not equal # of memory bus channels. As an example, the
Compaq Proliant 5000 quad Pentium Pro server had 16 DIMM slots but only a
single memory "channel". Back then they called it a "bus", which is the
proper electrical engineering term. "Channel" didn't come along until much
later when vendors started installing multiple memory buses. I guess the
marketing folks thought "channel" sounded better than "bus".

--
Stan


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