P5B=VM Memory Use

"Dewayne Thomas" <> wrote in message
news:...
> On Fri, 8 Jun 2007 17:16:43 -0400, "RobV" <>
> wrote:
>
>>Paul wrote:
>>
>>[snip]
>>
>>> Perhaps you could use CPUZ, to verify that the settings in the BIOS
>>> are being used.
>>>
>>> http://www.cpuid.com/cpuz.php
>>> http://www.cpuid.com/download/cpu-z-140.zip
>>>
>>> Compare the numbers, to the ratings for your RAM.
>>>
>>> The "registers dump" function, will make a text file for you, if you
>>> ever need to copy and paste any of the info. The raw SPD EEPROM info
>>> appears just below "Dump Module #1" etc.
>>>
>>> Paul
>>
>>Excellent suggestion.
>>
> Thanks, guys, I'll let the info I've gathered today cook awhile and do
> some more investigating with a register dump. Last resort I can jack
> the mem voltage up to where something smokes, then back off alittle.
> Just kidding.
>
> Dewayne
There is a separate isue, that has not been mentioned. Going to four
memories, also increases the loadings on the actual 'signalling' lines.
Historically (for instance), on the earlier AMD 64 chips, it was common to
find that memories that would run 'cas 2', with just two units fitted, had
to have the timings slowed to cas 2.5, when all four slots were used (on
these chips the memory controller is part of the processor), or the actual
memory clock rate had to be dropped from 400MHz, to 333Mhz. On latter
processor chips this was improved. Now on your board, the memory
controller is part of the motherboard, rather than the processor, but
similar loading problems, do sometimes appear. A google search on 'running
with all four slots full', will find literally tens of thousands of posts
about this, with a huge number of different motherboards. Historically,
this was why 'server' motherboards, supporting a lot of RAM slots, used
'registered' memory (where a buffer is present on the memory module
itself). The 'downside' of this, is that the buffer itself slows the
memory performance a little, but it was essential on boards which had more
RAM slots ...
You may well find, that you have to lower the actual memory clock rate a
little to get the system to work with all four slots filled.

Best Wishes

Most boards running in 32 bit mode that attempt to run all four RAM slots
run into timing instability. The recommended way to get 2 GB of memory in
such a case is to run 2 x 1GB sticks. Or switch to 64 bit OS.

--
---------------------
DaveW
"Dewayne Thomas" <> wrote in message
news:...
>
> I just put a system together using an ASUS P5B-VM with an Intel Core 2
> Duo 6400 CPU. I wanted to use 2 GB memory (4 sticks of 512MB Kingston
> DS) as listed in the manual as qualified memory for this MB. The
> system runs normal and stable with 1 GB mem, but with 2 GB, all four
> mem slots filled, it's unstable as hell and fails memtest big time.
> Using the settings listed on page 2-19 of the manual in all various
> combinations makes no difference. I left the mem & CPU voltages in
> auto as I really don't have a good feel for the impact they would have
> on the system if I imput something wrong.
>
> I have Win XP installed and it runs fine with 1 GB memory. I installed
> a ATI X 1950 Pro express 16 card in it but it ran fine with the
> onboard video also.
>
> Any one running this same MB with all mem slots filled, or have any
> suggestion on why the board wont handle 2 GB mem>
>

"Dewayne Thomas" <> wrote in message
news:

[...]

> Thanks, guys, I'll let the info I've gathered today cook awhile and do
> some more investigating with a register dump. Last resort I can jack
> the mem voltage up to where something smokes, then back off alittle.
> Just kidding.

Never exceed the RAM manufacturer's maximum voltage spec. RAM is too easy
to fry. With four sticks you'll probably need to run the RAM at its maximum
voltage (DDR2 max will probably be around 2.1v but check the manufacturer's
web site *first*) and also increase the voltage to the Northbridge
(typically from about 1.2v to about 1.4v).

"Robv" <> wrote in
alt.comp.periphs.mainboard.asus:

> Dewayne Thomas wrote:
>> I just put a system together using an ASUS P5B-VM with an Intel
>> Core 2 Duo 6400 CPU. I wanted to use 2 GB memory (4 sticks of
>> 512MB Kingston DS) as listed in the manual as qualified memory
>> for this MB. The system runs normal and stable with 1 GB mem, but
>> with 2 GB, all four mem slots filled, it's unstable as hell and
>> fails memtest big time. Using the settings listed on page 2-19 of
>> the manual in all various combinations makes no difference. I
>> left the mem & CPU voltages in auto as I really don't have a good
>> feel for the impact they would have on the system if I imput
>> something wrong.
>>
>> I have Win XP installed and it runs fine with 1 GB memory. I
>> installed a ATI X 1950 Pro express 16 card in it but it ran fine
>> with the onboard video also.
>>
>> Any one running this same MB with all mem slots filled, or have
>> any suggestion on why the board wont handle 2 GB mem>
>
> Anytime you add memory, that additional memory draws current,
> making the total load of the memory voltage higher. The fix is
> simple: go into the BIOS and increase the voltage for the memory.
> Increase by one step, test the system and if it is not stable,
> increase the voltage again. Repeat till you have stability,
> although you shouldn't have to go too far to fix the problem.

If your pc draws more current, still the voltage should stay stabilized
at 1.8V. I'm using 4 sticks of 1GB each on P5B Plus whithout any
problems.

If the voltage collapses because of drawing more current, the power
supply is insufficient.


--
regards, victor

> If the voltage collapses because of drawing more current, the power
> supply is insufficient.
>
>
> --
> regards, victor

not saying your wrong, just curious ..
isnt all of the power for the ram driven from the motherboard itself?..
(I know the Power comes from the PSU to the MOTHERBOARD.. but I wasnt sure
how much filtering/rectification took place on the mobo)

"mr deo" <> wrote in
alt.comp.periphs.mainboard.asus:

>> If the voltage collapses because of drawing more current, the
>> power supply is insufficient.
>>
>>
>> --
>> regards, victor
>
> not saying your wrong, just curious ..
> isnt all of the power for the ram driven from the motherboard
> itself?.. (I know the Power comes from the PSU to the
> MOTHERBOARD.. but I wasnt sure how much filtering/rectification
> took place on the mobo)

A chain is a strong as the weakest link.


--
regards, victor

"mr deo" <> wrote in
alt.comp.periphs.mainboard.asus:

>> If the voltage collapses because of drawing more current, the
>> power supply is insufficient.
>>
>>
>> --
>> regards, victor
>
> not saying your wrong, just curious ..
> isnt all of the power for the ram driven from the motherboard
> itself?..

Yes, but the MB cannot increase the power that the PSU delivers.

A chain is a strong as the weakest link, in this case the PSU.


(I know the Power comes from the PSU to the
> MOTHERBOARD.. but I wasnt sure how much filtering/rectification
> took place on the mobo)




--
regards, victor

On Sat, 9 Jun 2007 15:43:33 -0700, "DaveW" <> wrote:

>Most boards running in 32 bit mode that attempt to run all four RAM slots
>run into timing instability. The recommended way to get 2 GB of memory in
>such a case is to run 2 x 1GB sticks. Or switch to 64 bit OS.

Well I tried the 2 x 1GB sticks and memtest checks them as OK, but
boot to the operating system and video errors start. Streaks across
the screen. then screen junping. I tell you I have had it with this
board. The video card runs solid in other machines. Any one have a
suggestion on a ASUS intel MB thats running solid with 1 GB sticks in
two or four slots. Oh, bye the way, with the 2 GB memory ,(1 GB sticks
in two slots) no settings or combination of settings available in the
BIOS had any effect on the stability of the system. Any way, thanks to
all hands that offered suggestions and recommendations, Appreciate it.

Dewayne