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Hello everyone, in this lesson we will take a look at the standby conditions of IO and PCH

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The first is the standby condition of IO

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The standby condition of IO is relatively simple, only one standby power supply is needed

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The standby power supply is usually 3.3V

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And it is generally a power supply with VCCDSW_3P3

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The standby condition of IO is relatively simple

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Next, let's look at the standby conditions of PCHPCH

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The first is the four conditions of the RTC circuit

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First is VCCRTC

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VCCRTC is the power supply of the RTC circuit

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Ideally this voltage should be 3.3V

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But in the actual circuit, this voltage only needs to be about 3V.

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RTCRST#

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RTCRST# is the reset signal of the RTC circuit, and its voltage is generally equal to VCCRTC

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Further down, SRTCRST#

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It is also pulled up by VCCRTC

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So its voltage is generally equal to VCCRTC

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The last condition is the clock of the RTC circuit, which is the clock of 32.768KHz

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It is a waveform, so there is no specific voltage

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If we use a multimeter to measure this waveform, under normal circumstances,

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we can measure a voltage of about 0.1 to 0.5V

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Next is the standby condition of the PCH

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VCCDSW_3P3

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VCCDSW_3P3 voltage is the deep sleep standby voltage of PCH

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Generally, it is generated by 5VSB passing through a voltage regulator tube

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Next is DSW_PWROK

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This is a good signal for deep sleep standby voltage, usually sent by IO to PCH

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When the IO has a standby power supply, it will send a DSW_PWROK signal

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Next are VCCPRIM_3P3 and VCCPRIM_1P0

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These two are the main standby power supply of PCH, they are 3.3V and 1.0V respectively

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The last one is RSMRST#

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This is the main standby voltage signal of the PCH, which is also sent by the IO.

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These standby conditions are the conditions that the motherboard needs to have when it is in standby.

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Next, let's take a look at the measurement of these standby conditions in real objects

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The first is the standby power supply of IO

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We can measure it on the IO pin

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Here I have summarized a key pin of commonly used IO for you, including the item of standby power supply

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We can find the standby power supply pin of IO in this table, and measure whether it has power supply

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Next is VCCRTC

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It can be measured at the double diode near the coin cell

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Because the VCCRTC power supply is generally converted from the button battery through a common cathode diode.

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So we only need to find this common cathode diode near the button battery

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to measure whether the power supply of VCCRTC is normal

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Of course, not all button batteries have common cathode diodes near them, such as this motherboard

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There is no dual diode near the coin cell

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Look at the bitmap, you can see that its dual diodes are near the PCH

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This is harmless

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If we can't find VCCRTC, we can temporarily stop looking for it

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We go straight to measuring RTCRST#

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It is also a 3.3V power supply, which is pulled up by VCCRTC

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In other words, with RTCRST#, there must be VCCRTC

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RTCRST# can be measured on the CMOS jumper

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Because the motherboard usually has a CMOS jump cap, which is used to short-circuit RTCRST#

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Let's look for a CMOS jumper on this motherboard

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It is here

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It has two pins, one is ground and the other is RTCRST#

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We need to measure a voltage of about 3V on this pin

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Next is SRTCRST#

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If you don't look at the drawing, you really can't detect this signal

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So this signal we can skip it first and not measure it

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The next one is RTCX

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It is the crystal oscillator of the RTC circuit

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We can measure it directly on the crystal oscillator.

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A crystal oscillator has two pins

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We can use an oscilloscope to measure the pins of the crystal oscillator, or we can use a multimeter to measure

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The pin of the multimeter to measure the crystal oscillator should have a voltage of 0.1V to 0.5V

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Further down is VCCDSW_3P3

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This is a deep sleep standby voltage

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As we said before, it is generally the same as the standby power supply of IO

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So we can measure on the standby power supply of the IO,

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and also at the voltage regulator that generates this power supply

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But some motherboards will have two voltage regulators

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For example, this motherboard has a voltage regulator for main standby

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and a voltage regulator for deep sleep standby.

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When we measure, we need to distinguish

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In general, both regulators need to be powered

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Next is DSW_PWROK

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It needs to be measured on the IO pin

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This table has a standby good signal with measurement pins of DSW_PWROK and RSMRST#

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VCCPRIM_3P3, this is the main standby power supply of PCH, 3V

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The main standby 3V of this PCH will generally go to the B10 pin of the PCIE slot

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So we can directly measure on the B10 pin of the PCIE slot

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The B10 pin of the PCIE slot is this pin

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This side is A, this side is B

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The 10th foot from left to right is the B10 foot

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Next is VCCPRIM_1P0

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This is the main standby 1V voltage, generally there will be an inductance near PCH to generate it

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For example, this motherboard, its inductance is here

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So we can measure directly on the inductance

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The last one is RSMRST#

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It also needs to be measured on the pins of the IO

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Well, the above are the standby conditions of the 100 series PCH and IO

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The standby conditions after the 100 series are basically the same as those of the 100 series.

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We will talk about their differences later.