Robert said:
I ran several passes of memtest86 and the ram 'seems' to be ok.
However the computer crashes in XP and sometimes reboots.
I have an old ASUS A8S-X Motherboard and have installed [2] 1gb
modules.
The slots I placed these [2] 1gb modules in are Black and Blue, the
ones fartherest from the CPU.
Their are 4 total slots for this board, 2 blue and 2 black.
Did I make a mistake in not placing these 2 modules in the same color?
Was I suppose to place these modules into the blue slots?
The two blue slots are nearest the cpu.
The manual makes no mention of this but then again the manual sucks
about details.
Please help if you can, this is driving me crazy.
Here is an image of my motherboard, sorry I didn't post this first.
http://img266.imageshack.us/img266/3131/a8sxip7.jpg
This is going to take awhile
The A8S-X board is an S939 AMD system, where the memory controller is inside the
processor. The chipset is nominally SIS756, but it doesn't even touch the memory
sticks themselves, so identifying the chipset really doesn't help at all. Yet, that
doesn't prevent Ebay sellers from listing it, as a defining characteristic, when
a customer is interested in purchasing 1GB DDR memory.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=350023900824
*******
# Known to work with:
#
# *.VIA P4X266A,
# *.VIA KT266/333 (except ASUS KT266/333)
# *.VIA KT600 (except ASUS KT600)
# *.VIA PT800
# *.SIS 645
# *.SIS 648
# * 648FX
# *.SIS 746FX
# * KM400
# * K8T800
# * KT 880
# * KT 400 (except ASUS KT400)
# * KT 400A
# * SIS 661FX
# * SIS 655
# * SIS 650GX
# * SIS 650
# * NFORCE 250GB
# * ULI CHIPSETS
# * INTEL 915
# * NFORCE 4 SLI
# * VIA APPOLLO P4X400
* VIA K8M800
* VIA K8M890
* VIA K8N800
* VIA K8N890
* VIA K8T800
* VIA K8T890
* VIA K8T900
* VIA PT800
* VIA PT880
* VIA PT890
* VIA P4M800
* VIA P4M800 PRO
* VIA P4M890
* VIA P4M900
* VIA PN800
* SIS 648
* SIS 649
* SIS 650
* SIS 651
* SIS 656
* SIS 661
* SIS 748
* SIS 750
* SIS 755
* SIS 756 <----- Aw, gee. This chipset doesn't even *touch* the DIMM! S939 proc does though.
*******
So, the first question is, were the DIMMs purchased on Ebay ?
The closest analogy I can come up with, would be this. I'm shopping for a
used car in the newspaper. I see one that says "runs good in warm weather".
Now, what does that mean to me ? I want a car that "runs good" period! I
don't want arbitrary caveats listed to go with that description. The same
goes for a memory purchase - why would I be happy to have a "restricted"
list of applications that are valid for it. What if I want to resell the
memory, to a person owning an Intel computer ?
The Ebay RAM, 1GB DDR type, uses 128Mx4 chips. They are variously referred to
as "high density" RAM, due to the fact that the row/column addressing requires
an extra bit. That makes the RAM incompatible with chipsets like Nforce2 (only
half the memory detected). But on an AMD processor like Athlon64 or better,
I don't think that is a problem.
To make a bank of chips, it takes 16 chips of x4 width each, to populate the
64 bit wide interface on the DIMM. It means the memory controller needs to select
all the chips simultaneously, which apparently some controller can do. (Assert
both chips selects on the slot at the same time ?)
If you were to buy branded RAM, from Crucial/Kingston/Corsair or the like,
then they'd put 64Mx8 chips on the DIMM, which is a more standard configuration.
Such x8 chips are suitable for use with Intel chipsets, for example (like my 875P).
Intel does not approve the use of x4 chips on unbuffered DIMMs for desktops, in
any of the Intel datasheets that I've read. Which is why you'd notice no Intel
chipsets in the above "restricted" list. If you buy the Ebay RAM, it means not
being able to move it to your Intel board when you want to.
OK, next topic, is memory testing.
1) Memtest86+ - this is a program that you run, before booting the OS. It has
two characteristics. First is, it is capable of testing *every* memory location
(a good thing). It does this, by moving the executable out of the way, and
"testing underneath". As long as the BIOS does not reserve locations for internal
usage (E820 standard), memtest86+ can test it.
In terms of error detection, the main value of memtest86+ is detecting "stuck-at"
permanent memory faults. That is what it does best. It does not, however, detect
every possible transient problem. Which is why there are other tests...
2) Prime95 torture test - is a program that runs in Windows or Linux.
You use memtest, to determine it is "relatively" safe to boot into Windows. I've
had one guy, who passed memtest, booted to Windows, and corrupted Windows beyond
repair. So the test is not perfect. But if you get into Windows, you can use
Prime95.
Prime95 does a math calculation with a known answer. If it detects even one
error, it stops. A properly adjusted computer should be able to run Prime95
without stopping, for four hours or more. On my worst adjusted computer, it
will stop in ten seconds, and report an error. It is a more sensitive test
of memory, Northbridge, and CPU integrity (as sometimes the CPU is at fault).
With a new memory, we can test just one stick at a time. If there is a fault,
the test programs can immediately implicate just the one stick, and it can
be returned under warranty.
When two sticks are installed, now we're testing the noise sensitivity and
loading sensitivity of the memory controller. Some controllers "operate on
the edge of stability", like Nforce2 at DDR400 operating speed. Some controllers
are "wimpy", and need to be assisted, to work with all slots full.
On Athlon64, the "wimpy" factor is taken care of, by cranking down the memory
speed, or by using a 2T command rate. Both mechanisms seek to help the memory
controller, reduce noise, allow more setup time for address/command etc. The
processor has a lot of electrical activity (core computing and I/O pad switching),
which means when they stick a memory controller on there, with 144 signals
switching at the same time, it has some consequences for memory bus operation.
Your board can be operated a couple of ways, with two sticks. Placing one
stick in each blue slot (A1 and B1), means there is one stick per channel.
The blue slots are one per channel. So using the matched color pair of slots,
is a dual channel configuration.
The memory should be able to run at full speed, as in DDR400 Command Rate 1T,
with that config.
If you instead put the two DIMMs, next to one another, in an adjacent blue-black
pair, they'd be on the same channel (A1 and A2 say). Doing so, may cause the
BIOS to drop the RAM to DDR333 at command rate 1T. An alternate setting is
DDR400 at command rate 2T. So, if a channel has two double sided DIMMs on it,
the BIOS tries to compensate automatically, by using a more relaxed setting
than the RAM is rated for.
As mentioned in a previous post to you, adjusting Vdimm to 2.7V, from the nominal
2.5 or 2.6V, may help with memory operation. If only an occasional error is
seen in memtest86+, sometimes that is enough to fix it.
So, what can we do ?
1) Ebay RAM ? You decide what to do with it. My barge pole says "no way, Jose".
I would not buy RAM, unless it can be used in *any* motherboard. After all,
we don't want a car that "runs well, in warm weather only".
2) With quality branded RAM in place, using a total of two sticks, use the
dual channel (matched color) configuration. That will allow closer to rated
memory speeds to be used. Using four sticks on S939, or three sticks on S754,
requires some compromises on memory settings.
3) As with any memory purchased, even quality memory, you have some decisions to
make. Memory is so cheap, that it doesn't always receive good testing at the
factory. Depending on the costs associated with returning RAM, you can
adjust the timings or frequencies, to make the memory work. As long as you
can find some stable operating point, you may choose to keep the RAM.
On the other hand, you may choose to avail yourself of the warranty or
right to return "defective" product. If the memory will not meet the
timing advertised, then perhaps it is worth paying shipping to have
more sticks sent to you.
OK, so right now, you say you've passed memtest86+, so that means it was
"safe" to boot the OS. Now, if you want, you can get a copy of Prime95 and
test using that. This version is for Windows, and I like this one because it
can test up to a quad processor. No CD to make
Execute it, say no to
"Join GIMPS?" and just run it. If it stops with an error, you'll be visiting
the BIOS to tweak the memory settings. The leftmost menu has "stop" and "exit"
options, when you're finished.
http://www.mersenne.org/gimps/p95v255a.zip
That's it for now.
HTH,
Paul
