39
votes
Why are there separated power circuits for CPU, GPU, and RAM on a motherboard?
Because these chips require a lot of power, and that means a lot of current. A high-end CPU can pull over a hundred amps when running at full load! Having hundred-amp currents running all over your ...
- 35.2k
30
votes
Accepted
How do I desolder these specific points?
You need a bigger soldering iron, as in "more power."
The square connections are in the ground plane of the board. That is the large yellow area they are embedded in. That is a large piece of copper,...
- 72.5k
27
votes
Why motherboards have two pins for LEDs, led+ and led-
If the LEDs are driven using the most common method, as shown below.... you have no commons, no Vcc and no Ground.
If you have more than one LED you can not join any of those wires together either.
...
- 46.8k
19
votes
Why are there separated power circuits for CPU, GPU, and RAM on a motherboard?
What you're describing isn't really possible without silly amounts of decoupling.
A modern CPU might be drawing 100A, with 20A step changes in load, all at 1v DC, and wanting +-20mV. This is a ...
- 618
17
votes
Laptop motherboard not working, quiet clicking noise
Repair tech here! Solid analysis. I advise against injecting 18V, because your main power bus of the board is probably 12V or so, and there is a chance that the switching MOSFET that converts it to ...
- 3,613
16
votes
Accepted
Can Computer Motherboards Work Fine Even With A Damaged SMD Capacitor/Resistor?
You've just rediscovered Muntzing.
Quite often you can remove some specific component on a circuit board and the device will keep functioning - but not as well, capacitors being the primary target.
...
- 14.5k
14
votes
Accepted
What is this Lenovo 4-pin fan header?
Looks like they've just used a regular Molex 4-pin KK connector. This is as opposed to the standard fan connector which is a modified version with alignment pin designed to allow both 3-pin and 4-pin ...
- 67.8k
13
votes
Accepted
Is forcing power through a faulting board a good diagnostic tool?
It is a fairly standard technique when a node has a short circuit (low impedance) failure. The reason it is safe is that all of the current flows through the faulty device.
You do have to have some ...
- 29.4k
12
votes
Accepted
Accidentally knocked a capacitor off a laptop motherboard seemingly related to USB
It's a smoothing capacitor. They are used to smooth out transients in current draw by USB devices plugged in to the port.
If you plug in a device that uses large peak currents - such as a Wi-Fi ...
- 67.8k
10
votes
Accepted
Shared support chips and tooling between 16 and 32-bit computers
I'm going to skip the more general question as it would require a book, or more, to address. I'll focus on the x86 line, instead. I recall some of the context, making writing somewhat easier (if ...
- 78.3k
10
votes
Type of Header for Motherboard PWR Switch
This should be a standard 0.1" (2.54 mm) pitched header.
A name of that thing goes along the lines of SIL (single in line) female crimp housing (for the part which goes on the cable) with fitting ...
- 17.8k
10
votes
Accepted
mATX motherboard JFP1 header: Does not require pull-up or pull-down resistors, right?
Yes, normal case just has wires to LEDs and buttons like your drawing.
- 159k
9
votes
Accepted
Why are contacts missing on some of these M.2 modules?
The contacts are missing because they're not used. The A-key variant of the m.2 spec has provisions for display port signals while the E-key variant drops the display port and adds SDIO, UART and PCM (...
- 3,759
9
votes
How do I desolder these specific points?
Is there a special technique or tool I need to perform this task?
Nothing special but try to get hold of a rework station with blower. As pointed out by others, the square ones are indeed ground ...
- 91
9
votes
Why did a spark occur between my HDMI cable and metal lamp base?
If everything had been working previously in some configuration with the HDMI cable plugged in at both ends then my best guess is that there is a fault in your lamp. Maybe an earth has become detached ...
- 2,427
9
votes
PCIe implementation
Some hopefully helpful definitions:
PHY - Physical Interface - this is the electronic circuit that connects the innards of an IC to the physical PCB traces. Usually the PHY includes high speed SERDES ...
- 67.8k
8
votes
How do I desolder these specific points?
Most likely both pins are connected to planes. The ground plane on bottom layer is obvious, but there is probably a power plane on the other pin as well. So the solder will melt half way through the ...
- 79.5k
7
votes
Type of Header for Motherboard PWR Switch
A popular trade name or search terms got these are Dupont connectors. Even when not made by DuPont. Universal connectors for standard 0.1" headers.
Otherwise they can be found as female to male or ...
- 73.2k
7
votes
Accepted
Strange footprint labeled PJ## on laptop's motherboard
Solder Jumpers
Reason not sure why so big but yes they are solder jumpers for sure.
sometimes used to isolate a few MCU pins which might be conflicting otherwise connected during programming (...
- 9,321
7
votes
Signal and voltage
From Wikipedia:
A signal as referred to in communication systems, signal processing, and electrical engineering is a function that "conveys information about the behavior or attributes of some ...
- 21.4k
7
votes
Accepted
What are these white/grey stains on the back of a motherboard?
The lines seem to be surrounding all areas with exposed PTH leads sticking out, to the exclusion of areas with only SMD parts.
I think they mark the openings of something called a "selective wave ...
7
votes
Why are there separated power circuits for CPU, GPU, and RAM on a motherboard?
The short answer is that the 24 pin ATX power supply connector pins are not rated to supply enough power to today's high-end CPUs.
Since they probably want to keep things backwards compatible with ...
- 12.4k
6
votes
How can I adapt a 3-pin PC fan connector to a 4-pin connector?
This solved my problem:
Cited from 3pin to 4pin fan adapter(Chinese)
Explanation:
two fast-switch triodes (2N-2907 and 13003) utilize PWM control over 12v power.
diode protects the fan from voltage ...
- 161
6
votes
Accepted
USB 3.0 Bandwidth Per Individual Port
The short answer from the USB spec, each port has a maximum throughput of 450 MB/s. But the USB 3.0 PCIe Host controller interface has a maximum throughput of 500 MB/S. USB 3.1 raise this to 1GB/s by ...
- 21.8k
6
votes
Accepted
6
votes
mATX motherboard JFP1 header: Does not require pull-up or pull-down resistors, right?
Intel front panel connector can be somewhat confusing.
The switches should present no problem, simply connect them to corresponding pairs of pins.
The HDD LED requires correct polarity, but ...
- 12.9k
6
votes
Why did a spark occur between my HDMI cable and metal lamp base?
If you aren't in the US, ignore this answer. Also, be very careful with live outlets.
The problem could be a miswired plug. You can buy an outlet tester for a few bucks at a hardware store. They light ...
- 351
6
votes
Accepted
Can anyone identify this SMD?
Putting things into context, the circuit in the picture is about Ethernet interface.
The component CL2 has a connection to Ethernet socket metal shell. Thus it must be the common mode capacitor ...
- 159k
5
votes
Help identifying a possible connector for these unterminated contacts on my HP Stream 14 motherbard
That looks like a footprint for an M.2 connector (though not the exact one in the picture below). Specifically, it looks like an "M key" connector, so it could be connected to a PCIe interface and/or ...
- 511
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