RAM questions

  • Thread starter Thread starter tungley
  • Start date Start date
T

tungley

About to build a new pc, though it's been a while since I did my last. Can
someone point me to a primer or other page where I can read about and make a
decision as to the differences between buffered and unbuffered, and what ECC
Registered is? I don't remember those terms, and haven't kept up with the
subject. I want to order online, but don't want to make a mistake.

Basically, I'm going to build an Athlon 64 based system, and want to pick the
right RAM (pc 3200, I do know that). But those other terms are throwing me.
Also, must RAM be installed in pairs, or will the mobos allow single sticks? Or
is that mobo specific?

Thanks in advance.
 
tungley said:
About to build a new pc, though it's been a while since I did my last. Can
someone point me to a primer or other page where I can read about and make a
decision as to the differences between buffered and unbuffered, and what ECC
Registered is? I don't remember those terms, and haven't kept up with the
subject. I want to order online, but don't want to make a mistake.

Basically, I'm going to build an Athlon 64 based system, and want to pick the
right RAM (pc 3200, I do know that). But those other terms are throwing me.
Also, must RAM be installed in pairs, or will the mobos allow single sticks? Or
is that mobo specific?

Thanks in advance.
Click to expand...

Popular forms of memory are:

1) unbuffered without ECC
2) unbuffered with ECC
3) registered with ECC

ECC is error checking and correction. It allows both transient and
certain permanent errors to be corrected. ECC is a way of reducing
the error rate seen by the user - if what you are doing needs that
kind of certainty, and the processor and motherboard support ECC,
the extra few bucks are worth it.

The purpose of registered memory, is to insert a register chip between
the motherboard and the memory chips. The register chip "buffers"
the signals coming from the motherboard. Instead of a dual sided
module placing 16 loads on the address bus, it only puts 1 load
(the register chip), and that is much easier for the memory
controller to drive.

A motherboard that is designed with registered modules in mind,
will support more memory modules on the motherboard. So throwing
registers into the design helps with bus loading, and with the max
amount of memory the system will support. Registered is thus quite
popular on server motherboards, where customers place an emphasis
on the total memory they can use. (And some registered modules have
up to 36 memory chips on them, while unbuffered would be 18 chips
max before there is too much load.)

Athlon 64 is now available for three platforms. S754 and S939
use unbuffered DDR (like PC3200). The new AM2 uses DDR2 memory.
I think architecturally, all Athlon 64 processors support ECC,
so you can buy your memory with or without ECC protection.

To avoid mistakes in purchasing memory, you can visit crucial.com
or kingston.com and use their motherboard search engine. The
companies that make the motherboards, also provide downloadable
user manuals. The user manual for the motherboard will state what
kind of memory it uses. It should be reasonably easy to figure
out what memory to use.

"Memory in pairs" is for dual channel operation. S939 and AM2
have the memory slots arranged on two channels. By placing a
stick on each channel, it is possible for the processor to
fetch 128 bits in one clock cycle, instead of just 64 bits
from a single module. So "memory in pairs" means extra
memory bandwidth if you need it.

Paul
 
Popular forms of memory are:

1) unbuffered without ECC
2) unbuffered with ECC
3) registered with ECC

ECC is error checking and correction. It allows both transient and
certain permanent errors to be corrected. ECC is a way of reducing
the error rate seen by the user - if what you are doing needs that
kind of certainty, and the processor and motherboard support ECC,
the extra few bucks are worth it.

The purpose of registered memory, is to insert a register chip between
the motherboard and the memory chips. The register chip "buffers"
the signals coming from the motherboard. Instead of a dual sided
module placing 16 loads on the address bus, it only puts 1 load
(the register chip), and that is much easier for the memory
controller to drive.

A motherboard that is designed with registered modules in mind,
will support more memory modules on the motherboard. So throwing
registers into the design helps with bus loading, and with the max
amount of memory the system will support. Registered is thus quite
popular on server motherboards, where customers place an emphasis
on the total memory they can use. (And some registered modules have
up to 36 memory chips on them, while unbuffered would be 18 chips
max before there is too much load.)

Athlon 64 is now available for three platforms. S754 and S939
use unbuffered DDR (like PC3200). The new AM2 uses DDR2 memory.
I think architecturally, all Athlon 64 processors support ECC,
so you can buy your memory with or without ECC protection.

To avoid mistakes in purchasing memory, you can visit crucial.com
or kingston.com and use their motherboard search engine. The
companies that make the motherboards, also provide downloadable
user manuals. The user manual for the motherboard will state what
kind of memory it uses. It should be reasonably easy to figure
out what memory to use.

"Memory in pairs" is for dual channel operation. S939 and AM2
have the memory slots arranged on two channels. By placing a
stick on each channel, it is possible for the processor to
fetch 128 bits in one clock cycle, instead of just 64 bits
from a single module. So "memory in pairs" means extra
memory bandwidth if you need it.

Paul
Click to expand...

Thanks for such a good explanation. I'm going with a socket 939 board. I get the
explanation on the dual channel thing, but did you mean that if the board is
setup for dual channel, I MUST use pairs? Or can you do it either way?
 
tungley said:
Thanks for such a good explanation. I'm going with a socket 939 board.
I get the explanation on the dual channel thing, but did you mean
that if the board is setup for dual channel, I MUST use pairs? Or can
you do it either way?
Click to expand...

The S939 revision E processors can use any RAM configuration you
wish. (If you use an oddball mix of RAM, it runs all the sticks
in single channel mode.)

All S939 boards can work with one stick. With processors previous
to the Revision E processors, that one stick would only work
in two of the four slots. That was because one channel was the
primary channel, and the other channel could only be used for
installing the "upper 64 bits" of a 128 bit wide chunk. The
revision E processors fixed that, so a single stick could go
into any slot.

This is an example of a revision E processor. This one is E3.

http://www.amdcompare.com/us-en/desktop/details.aspx?opn=ADA3500DAA4BP

This one is a CG, and if using a single stick of RAM, the RAM would
work in 2 of the 4 slots.

http://www.amdcompare.com/us-en/desktop/details.aspx?opn=ADA3400AEP4AX

Not a big deal, but with the CG processors, it pays to match
the sticks, as to use all four slots, you'd want two matched
pairs. You can compare the PIB (processor in box) code from the
website you plan to buy the processor from, with the desktop
entries on the amdcompare.com web site, to figure out what
they are.

I expect the Revision E processors will be the cheapest ones,
and the older stock will likely stay at the original high
prices. That should help you get the right kind.

For best performance, a pair of matched sticks is the best choice.
There is a setting in the BIOS called the "command rate", and it
can be set to 1T when you use two sticks. That allows one command
per clock cycle, to be sent to the memory. It is about 20% more
efficient than the 2T setting.

If I was buying an S939 motherboard right now, I would buy 2x512MB
PC3200 memory. That would be my "economy" config, suitable for
most gaming and use with WinXP. If you want the extra elbow-room
that a couple of games like in the RAM department, then 2x1GB
PC3200 would be the way to go. The two machines I game on here,
have 2x512MB, and I haven't bothered to update them.

There should not be a price premium for splitting your RAM
into two sticks. If you shop around, whatever single stick you
were planning on buying, you could likely find two half-sized
sticks for about the same price.

And check the crucial.com site, to see what kinds of sticks
they list for your new motherboard. Just to get a little
more guidance.

Paul
 
The S939 revision E processors can use any RAM configuration you
wish. (If you use an oddball mix of RAM, it runs all the sticks
in single channel mode.)

All S939 boards can work with one stick. With processors previous
to the Revision E processors, that one stick would only work
in two of the four slots. That was because one channel was the
primary channel, and the other channel could only be used for
installing the "upper 64 bits" of a 128 bit wide chunk. The
revision E processors fixed that, so a single stick could go
into any slot.

This is an example of a revision E processor. This one is E3.

http://www.amdcompare.com/us-en/desktop/details.aspx?opn=ADA3500DAA4BP

This one is a CG, and if using a single stick of RAM, the RAM would
work in 2 of the 4 slots.

http://www.amdcompare.com/us-en/desktop/details.aspx?opn=ADA3400AEP4AX

Not a big deal, but with the CG processors, it pays to match
the sticks, as to use all four slots, you'd want two matched
pairs. You can compare the PIB (processor in box) code from the
website you plan to buy the processor from, with the desktop
entries on the amdcompare.com web site, to figure out what
they are.

I expect the Revision E processors will be the cheapest ones,
and the older stock will likely stay at the original high
prices. That should help you get the right kind.

For best performance, a pair of matched sticks is the best choice.
There is a setting in the BIOS called the "command rate", and it
can be set to 1T when you use two sticks. That allows one command
per clock cycle, to be sent to the memory. It is about 20% more
efficient than the 2T setting.

If I was buying an S939 motherboard right now, I would buy 2x512MB
PC3200 memory. That would be my "economy" config, suitable for
most gaming and use with WinXP. If you want the extra elbow-room
that a couple of games like in the RAM department, then 2x1GB
PC3200 would be the way to go. The two machines I game on here,
have 2x512MB, and I haven't bothered to update them.

There should not be a price premium for splitting your RAM
into two sticks. If you shop around, whatever single stick you
were planning on buying, you could likely find two half-sized
sticks for about the same price.

And check the crucial.com site, to see what kinds of sticks
they list for your new motherboard. Just to get a little
more guidance.

Paul
Click to expand...

Thanks again. My whole intent was to try to not end up with small size sticks,
once I started upgrading my memory total. I wanted to try a 1GB stick by itself,
then increase the memory by 1GB each time, up to the board's limit of 4GB (if
and when I needed that much). In the past, I'd always end up with sticks that
were too small to use together to get what I needed, then I'd have to give them
away, try selling them, etc. But I need to be realistic -- I don't game at all,
don't do CAD, etc -- so the likelihood of me needing more than 2GB (even 1GB) is
remote, so I'll likely go with 2X512mb.
 
Thanks again. My whole intent was to try to not end up with small size sticks,
once I started upgrading my memory total. I wanted to try a 1GB stick by itself,
then increase the memory by 1GB each time, up to the board's limit of 4GB (if
and when I needed that much). In the past, I'd always end up with sticks that
were too small to use together to get what I needed, then I'd have to give them
away, try selling them, etc. But I need to be realistic -- I don't game at all,
don't do CAD, etc -- so the likelihood of me needing more than 2GB (even 1GB) is
remote, so I'll likely go with 2X512mb.
Click to expand...

Interesting new information I found out. The board I've ordered is an Asus A8V -
found out that it can't use all four slots when using 400mhz (pc3200) memory.
So, if I bought 2x512mb (pc3200) sticks, and I wanted to later add RAM, I'd
never be able to use those sticks with this mobo, since the other two slots are
always disabled when using 400mhz sticks. If I want to use all four slots, I
need to use 333mhz (pc 2700) memory. Apparently that's a pretty common
phenomenon - many boards can't keep up with the memory at 400mhz across all four
slots (according to tech support people at Kingston and Crucial - both very nice
and helpful people, by the way). Glad I looked into it, since all the memory
choices was making me dizzy.....I'm told I shouldn't notice the slight
difference between the 2700 and 3200.
 
You can continue to use PC3200 DDR, but the mainboard downclocks it by
default if you populate all 4 DIMM slots. Here is Asus' take on that,
although it's not very informative:

http://support.asus.com/faq/faq.aspx?no=0893A1B0-95DD-47FF-34F4-9FEE2D69C14C&SLanguage=en-us

It suggests manually setting the memory frequency back to 200 MHz (x 2 for
double data rate, 8 bytes wide, gives 3200 MB/s). That may be more reliable
if you set the command rate to 2T in the bios, which is slower than 1T.

I'd recommend going to two 1 GB sticks immediately, if you can afford it.
That ought to eliminate most of the RAM issues.

Incidentally, if you're planning on using the 32 bit version of Windows XP,
it does not make 4 GB of RAM available to Windows applications. The
workstation boxes I've seen at work have 4 GB installed, but the amount
shown in Windows is rather less, perhaps 3.2 GB. If you really need 4 GB,
you might prefer XP64 (or a 64 bit version of Vista, in early 2007).

An A8V is an old board, but I had good luck with an A8V Deluxe (much the
same, but with an added RAID controller and Firewire). I hope that you enjoy
yours. I wouldn't recommend buying an AGP mainboard at this time (AGP is so,
like, 2004), due to the better variety of graphics cards for PCI-Express,
but maybe you have a good AGP card that you wish to continue to use.


Address scrambled. Replace nkbob with bobkn.
 
You can continue to use PC3200 DDR, but the mainboard downclocks it by
default if you populate all 4 DIMM slots. Here is Asus' take on that,
although it's not very informative:

http://support.asus.com/faq/faq.aspx?no=0893A1B0-95DD-47FF-34F4-9FEE2D69C14C&SLanguage=en-us

It suggests manually setting the memory frequency back to 200 MHz (x 2 for
double data rate, 8 bytes wide, gives 3200 MB/s). That may be more reliable
if you set the command rate to 2T in the bios, which is slower than 1T.
Click to expand...

Thanks for the link and info. The tech support people I spoke to said the board
would automatically disable the other two slots if two 400mhz sticks were
inserted. If it simply rolls them back, but still allows them all to be used,
I'm fine with that.
I'd recommend going to two 1 GB sticks immediately, if you can afford it.
That ought to eliminate most of the RAM issues.

Incidentally, if you're planning on using the 32 bit version of Windows XP,
it does not make 4 GB of RAM available to Windows applications. The
workstation boxes I've seen at work have 4 GB installed, but the amount
shown in Windows is rather less, perhaps 3.2 GB. If you really need 4 GB,
you might prefer XP64 (or a 64 bit version of Vista, in early 2007).
Click to expand...

Yeah, I've read about that recently. No biggie right now.
An A8V is an old board, but I had good luck with an A8V Deluxe (much the
same, but with an added RAID controller and Firewire). I hope that you enjoy
yours. I wouldn't recommend buying an AGP mainboard at this time (AGP is so,
like, 2004), due to the better variety of graphics cards for PCI-Express,
but maybe you have a good AGP card that you wish to continue to use.
Click to expand...

That's entirely the reason I'm going that route. Spent a lot of cash on an ATI
AIW Radeon a while back, and don't feel like investing in any new hardware
unless I have to. My needs are simple (no gaming, etc) so SLI, PCI-Eetc is no
big deal for me just yet. Just want a big speed jump from the old Asus I have
right now - even if it's just for the next 2-3 years.

Thanks again.
 
So Vista 64bit could use all 4 gig ddr400 ? In my Vista Beta2
tests, I'm seeing the hard drive run constantly .. as if the system
did not have enough ram. Test box is AMD 64 3700 with 2 gig
ddr400, and nVidia 7900 GTO ... and yet it is sluggish, and
the drive light is on all the time ?????? I'm trying to pin down
what the proper upgrade of this box should be. I could go to
4 gig ram, or I could upgrade to X2 3800 to get help from the
dual processor ??? Don't know. Can't even guess. I've got a
2nd box .. Dell Precission 9100 with nVidia 6800 .. with Vista
Beta2 on it, and I see somewhat the same problem. The Dell
is all Intel mobo, so Vista had the correct drivers for everything.
Still, again, hard drive is constantly accessing. The Dell is
a dual processor P4.

johns
 
Back
Top