Archived from groups: alt.comp.periphs.mainboard.asus (
More info?)
"Paul" <nospam@needed.com> wrote in message
news:nospam-0107051313070001@192.168.1.178...
> In article <da1vid$bsn$1$8302bc10@news.demon.co.uk>, "Oldish sod"
> <SpamDiddlyDooDoo@noway.nowhere.con> wrote:
>
>> "Drummer@Home" <spamoff!drummer@mail.inet.hr> wrote in message
>> news:d9uthv$smu$1@ss405.t-com.hr...
>> > Greetz ppl! I'm trying to lower the voltage so my cpu would be set to
>> > default 1.45, just to reduce the temp. I don't want to overclock, I
>> > just
>> > want to set the system running so kool it wouldn't need a rear case
>> > fan.
>> > But this board doesn't seem to allow voltages lower than 1.575, and
>> > that
>> > is 8% higher than Mobile needs. I got the latest 1009 beta bios. I've
>> > read
>> > the thread on "options for undervolting", but the 8RDAVcore seems only
>> > to
>> > support the A7N8X 2.0 version. Any ideas? Tweaked BIOS? No "wire mods"
>> > please!
>>
>> I've looked at doing this for some time on an A7N8X del. 2.0, and I've
>> come to the conclusion that it's not possible to undervolt Vcore on this
>> mobo, whatever revision/version.
>> I've not even seen any 'wire mods' (anyone know of one?)
>> I'm not really complaining though as I bought it for overclocking, and
>> ran an XP2500 as a 3200 for a couple of years, so..
>
> There is another tool that can change VID setting. It is called
> CPUMSR, but it doesn't seem to work with Nforce2 boards. The
> board will freeze if you try to change the voltage (and the
> processor used, must be a XP-M mobile, or be an ordinary chip
> modded to become a mobile, to work with CPUMSR). I'm not at all
> certain how this is supposed to work at the hardware level, as
> the description on the CPUMSR web page suggests there are "softVID"
> pins as well as the ordinary VID pins on a Mobile processor.
> Since I cannot download a Mobile datasheet, this is hard to
> verify.
>
> This page shows the wire mods graphically:
>
>
http://www.ocinside.de/go_e.html?/html/workshop/pinmod/amd_pinmod.html
>
> If you select "Socket view", and set Vcore to "1.85 volts",
> you'll see an example of what area of the processor socket
> gets the wires added.
>
> PDF page 66 of this document, shows the five VID socket holes on
> the left hand side (see the pins on row "L"). Connecting a pin to
> VCC is a logic "1" and alternately connecting to VSS is a logic "0".
> You'll notice that VID4 has easy access to VSS, but not VCC, so
> forcing a logic "1" on there could be a bit dangerous, if a long
> bare wire is required. That would be a PITA if you need to set VID4
> to logic 1. Insulating the wire could cause the processor to not
> sit flat, causing poor CPU cooling.
>
>
http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/26237.PDF
>
> In the same document, the "desktop" voltage table is shown on
> PDF pg.90.
>
> If you are using an AthlonXP-M processor, the VID voltage table for
> that can be found on fab51:
>
>
http://fab51.com/cpu/barton/athlon-e23.html#L11
>
> The L11 table shows the correspondence between mobile and desktop
> processors. My "Q" for example, would draw 1.450V if inserted in
> a mobile motherboard, and instead it shows as 1.575V on my A7N8X-E.
> That means VID4..VID0 values are 01011, as page 90 of the 26237.PDF
> document shows 1.575V being 01011 binary value.
>
> Looking at the table, the nearest convenient voltage value with
> respect to 1.575V (01011) would be 1.475V (01111). I picked that
> case because only one piece of wire would be needed to change
> VID2 from logic "0" to logic "1". A wire inserted in socket hole
> "L5" joined to "M4", would connect VID2 to VCC ("1"). The BIOS
> Vcore setting _must_ be set to "Auto" when you do a wire mod,
> as you do not want the BIOS fighting with the electrical short
> caused by the wire. If you select a non-Auto Vcore value in
> the BIOS, there have to be some GPIO pins somewhere that are being
> used to drive the VID pins, and you have no way of knowing
> exactly how Asus is doing it. A selection of "Auto" _should_
> cause the BIOS to tristate the GPIO pins, so there is no
> contention between wires and GPIOs.
>
> Another thing to consider, is the electrical spec of the processor
> itself. A careful experimenter will also want to check that the
> wires will not damage the processor.
>
> Table 10. VID[4:0] DC Characteristics
> Parameter Description Min Max
> IOL Output Current Low 6 mA ---
> VOH Output High Voltage 5.25 V *
>
> What this means is, when the processor VID pin makes a "0",
> it can sink up to 6 milliamps without damage. Connecting a wire
> to VCC (1.5 volts) to force a "1", pumps current into that
> signal, potentially violating the spec. If the VID pin is
> trying to make a "1", it is effectively an open circuit, and
> a voltage of up to 5.25 volts can be applied to it. (The Vcore
> regulator has pullup resistors connected to some voltage, and
> that is the purpose of specifying the 5.25 volts, so if the
> Vcore regulator connects its pullup resistors to +5V, there
> won't be breakdown damage to the VID pins.)
>
> What does this say about our proposed VID2 wire mod above ?
> It says we could potentially damage the VID2 signal, but I suppose
> people do this all the time. I would say according to the Athlon
> spec, forcing VID signals to "0" is safe, while forcing them
> to "1" we really cannot be sure what will happen to the processor
> in the long term. (There is no way to know whether the processor
> VID pin is simply a bond wire to ground inside the package, or
> is an open drain transistor connected to a lasered fuse - to assess
> the situation properly, you would want to do an I versus V curve
> for the pin, to get some idea of what structure drives it inside
> the package).
>
> To answer this question, we can consult a venerable source:
>
>
http://web.archive.org/web/20040412055223/www.beachlink.com/candjac/slotAocg.htm
>
http://web.archive.org/web/20031208175846/www.beachlink.com/candjac/gfds.htm
>
> The claim here is, that resistors are being used by the processor
> for setting VID. This means you can use VCC or VSS to program
> the value on a VID pin, with less to worry about. My worry was
> that these pins were driven by transistors. The Athlon Model10
> datasheet mentions "strapped" (which informally means resistors
> in engineering-speak), and if you believe the info on PDF page
> 50 of the datasheet, the resistors inside the processor are
> 150 ohms (whereas the candjac site states they are 100 ohms).
>
> The candjac "gfds.htm" page mentions another issue, and that is
> whether a wire mod of a VID pin to VCC, gives enough voltage
> to make a valid logic "1". According to my notes, the A7N8X
> uses a L6917B voltage regulator (a 28 pin chip to the left of
> the processor socket). The datasheet for that part says the
> VID pins are "TTL compatible", which, one would hope, means
> anything more than 0.8V would give a logic 1. Since the wire
> mod is actually using the Vcore voltage to make the logic 1,
> the lower you set Vcore, the less adequate the logic 1 becomes,
> that you are sending to the VID pins on the L6917B. Since
> Vcore won't be set lower than about 1.3V or so, this shouldn't
> be a problem (and you'll be able to see in Asus Probe, whether
> the wire mod is working anyway).
>
> So, it looks like the wire mod should work OK
>
> Why did I go through all this ? To show that wire modding is
> not a trivial art
There are some Intel processors, where
> this same technique would not be appropriate, so the ideas
> don't necessarily transfer to other situations. A good mod
> should be reversible and not leave traces of what you've
> done
Now that's what I call a comprehensive answer. Many
thanks, Paul! 'Will have to re-re-read, though..
OT, this kind of stuff reminds me of a calculator (Casio,
FX-something, I think) many, many moons ago when at
'college' - it cost 12 'units', but the guy next to me paid
3 times as much for his, as it had polar/rectangular
coordinate conversion buttons. Turned-out he paid
3 times as much for a bit of extra 'silk-screen' printing
on the keypad (confirmed when tried on mine).
This'll be a little trickier!
Regards,
--
Rob
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