Questions tagged [computers]

Questions regarding architectures or design of specific parts, not consumer-related questions.

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3 answers
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What can be done with all of the extra address lines in a ROM? Why were they designed to have so few outputs compared to possible inputs?

I am a student in an introductory Digital Logic and Computer Systems course. We have been learning about ROMS, but often we just use them to basically just map truth tables onto them. We have been ...
-1 votes
2 answers
118 views

Configuring an astable 555 timer to milliseconds

I am working on a Tinkercad project and I would like a 555 astable clock for it. I am trying to configure the astable 555 timer for every millisecond (or something close). I don't know how to do it, ...
2 votes
4 answers
752 views

History, reason for and implications of the 2 modes of a modern microprocessor?

The modern microprocessors I've dealt with could have 2 modes: User and superuser (and sometimes this difference was just in the manual and not actually implemented like with the Nios II which states ...
1 vote
1 answer
114 views

Solder pads ripped - charging via test pads?

My uncle asked me to repair a tablet but when I opened the tablet I saw that the micro USB connector was completly ripped off the board and I lack the tools to scrape free some of the copper to solder ...
3 votes
2 answers
7k views

Are there gate-level ways to produce the min or max of two binary values?

Some basics of digital logic are the half-adder and full-adder. We know how to produce the sum of two binary values at the level of AND/OR/NOT gates, in a straightforward way presented in many ...
1 vote
0 answers
43 views

A problem with an old computer PSU (schaffer-bv-223-5-04008)

I'm trying to find out the reason why an old PSU is not providing output voltage. Some times ago, I asked for help on retrocomputing (here is the thread: schaffer-bv-223-5-04008 unidentified ...
1 vote
4 answers
2k views

How can a powersupply have a large input volt range

I see that computer power supplies that can take a voltage input of anything between 90V and 260V at a frequency between 47Hz and 63Hz. Meanwhile it can output power at a very precise voltage. How ...
-1 votes
2 answers
1k views

Power supply makes a static/coil whine noise when the power supply is off and the PC is off

I have noticed that my power supply (PSU) makes a VERY slight coil whine/static noise while it is plugged into the power outlet, regardless of the power status of the PC and the PSU. It sounds no ...
0 votes
2 answers
143 views

Power electronics on a PCI/PCIe expansion card

I'm not sure if its been done before but how feasible is the idea of building an computer expansion card (PCI/PCIe) that carries mains power on some areas of the expansion card being switched by ...
0 votes
2 answers
222 views

Why do server mainboards use different capacitors for their VRMs?

Recently I noticed that server mainboards use a different type of capacitor as part of their VRMs (after the inductor). I believe they are ceramic capacitors, whereas consumer boards usually use ...
0 votes
1 answer
95 views

Building a battery powered computer system

I want to power a PC, monitor and modem with one deep cycle 12 V lead-acid battery. The PC is a mini-ITX board with intel N100 CPU. It consumes between 10-40 W depending on usage and has a 19V DC ...
0 votes
2 answers
835 views

Wiring a USB-C (host) cable question

I have wired some custom USB-C cables from scratch in the past, where the USB-A connector is plugging in to a host PC. If I wired a USB cable where the USB-C connector was plugging into a host ...
0 votes
1 answer
271 views

How do I send a signal from my computer to my USB antenna

I'm trying to make an RC car that can be controlled by my computer. The heart of the car is a simple mother board from an old toy. It basically accepts a signal 49MHz from a controller with a 9V ...
2 votes
4 answers
758 views

How damaging are inrush currents?

Typical power supplies will have 30 to 100 amps inrush current at 220v, sometimes less, sometimes over that. How is it that the power strip rated at max 10amps at 220v doesn't get damaged? Also, if I ...
7 votes
3 answers
2k views

How did the vacuum tube computer technicians know when a tube had failed?

I have read that in vacuum tube computers, a tube would fail every couple of days. How did the technicians know that a tube had failed? Wouldn't a broken tube silently cause the calculations to ...
1 vote
3 answers
489 views

How does a PC switch turn on a PC?

Here is my current level of understanding: virtually every PC case has a switch near the top to power on the PC. When the PC is off, pressing the switch once will power it on and the PC will begin ...
0 votes
1 answer
305 views

using citric acid alcohol solution to clean rusted terminals

I used to clean old computer sockets and terminals with citric acid solution in alcohol. It worked fine for long time, but for the tiny connectors of DIMM Ram sockets it works for a very short time ...
5 votes
3 answers
4k views

How to combine PC's power and HDD LEDs?

I'm going to buy a PC tower case that has only one LED intended to be used as the power LED, and no separate HDD LED is available. My intention is to have that single LED lit at about 50% of its ...
2 votes
3 answers
312 views

Why do inductors in motherboard VRMs have high-voltage build-up without diodes?

I just watched Bullzoid/Actually Hardcore Overclocking's video on how VRMs actually work, and I have a question. First, in my understanding, the diodes in the VRMs are included to stop the inductor ...
1 vote
3 answers
241 views

Electrical/physical difference between Primary Memory and Secondary Memory connection to CPU

It is said that the difference between primary memory and secondary memory is that primary memory is "directly accessible by CPU", while secondary memory is "not directly accessible by ...
0 votes
1 answer
637 views

Is it possible to make a keyboard with "Game Controller" style printed circuit boards and buttons?

For a long time I've wondered if it's possible to make a keyboard with PCBs similar to the ones used in NES controllers or just video game controllers in general. If it can be done with keyboards it'd ...
7 votes
6 answers
943 views

Why are flip-flops criss-crossed?

I want to simulate how a computer works using logic gates. Right now I am trying to build the memory aspect of it. After looking at various articles and books I see a lot of them using flip-flops/...
0 votes
2 answers
238 views

USB inrush current limiting, charging super capacitor

I am trying to charge a supercap over USB. I understand I need to limit the current (ref: usb.org) This has been discussed a lot here, for example: here and here, but I believe my requirements are a ...
1 vote
2 answers
97 views

Problem with the smallest negative number using Signed-2's-Complement

I have a problem figuring out why the smallest negative number we can represent in 3 bits, using Signed-2's-Complement is -4. I understand that in S2C format, we can create numbers from 2x-1-1 (...
1 vote
1 answer
819 views

Is the purple wire on an ATX power supply always +5V stand by?

I'm trying to use an old 20 pin ATX power supply as a substitute for the failed power supply in a Dell Optiplex 7040† I managed to find the pinouts for the Dell power supply which only has two output ...
3 votes
5 answers
2k views

Voltage-drop resistor to power a 19 V computer

I am considering using a voltage-drop resistor to drop the 21.6 V ± 1% on a power supply down to 19 V. If this was an LED, I would use a 1 Ω, 7 W resistor but this seems to be a very big size. In this ...
0 votes
6 answers
1k views

Is there a practical reason for making laptop AC adapter bricks at the plug end?

All laptops require a AC adapter in order to convert electricity into a usable form for the laptop. In most AC adapters I've seen, the plug is directly connected to the power brick, meaning that the ...
1 vote
1 answer
128 views

trying to 'grab' information ( data ) from a computer usb and using it in a programe ( python )

I was wondering if i could use my own computer to interact with the real world.So, if i have a sensor of some sort plug it in via USB or a certain information from a USB , then can i get the data ...
0 votes
1 answer
85 views

Reset mainboard from Raspberry Pi

I have a desktop computer with an Asus mainboard TUF_GAMING_B550-PLUS and a Raspberry Pi 4. I log in remotely to the computer, but unfortunately from time to time it has an operating system issue, ...
12 votes
8 answers
5k views

How many transistors at minimum do you need to build a general-purpose computer?

I'm wondering what the simplest design for a general-purpose (Turing complete) computer is. To my surprise, I haven't found much on the web. Surely this is a known problem?
0 votes
1 answer
45 views

How to connect an activity LED to a RocketRAID card? [closed]

So this is more computer-based, but definitely electrical so I'm hoping I can find some help, so here goes... I have a home server (WSE2016) which utilizes a RAID for its primary storage. I had an ...
3 votes
3 answers
6k views

Low Voltage DC Automatic Transfer Switch

I am new to circuits and have a very basic knowledge, and am currently interested in building a simple circuit that would take 2 DC inputs each of 12V 1.5A and output 1 x 12V 1.5A input even if 1 of ...
1 vote
2 answers
43 views

Driving a DVI monitor from a monochrome source

I have a plasma display EL8358MS that is defective (burnt out.) The display has a signal convertor with these inputs: ...
0 votes
2 answers
98 views

How are the transistors in motherboard controlled and timed?

I just watched Bullzoid/Actually Hardcore Overclocking's video on how VRMs actually work, and I have a couple questions. In the video, the Bullzoid mentions how the transistors are switched on and off....
2 votes
6 answers
163 views

Confusion regarding future scope of electrical & electronics engineering jobs (generally world wide and especially in India) [closed]

This question is seeking advice generally for world wide and especially for Indian region(India and its neighbour countries having almost same economic conditions like India) If anyone has no idea ...
2 votes
1 answer
621 views

Why do SSDs have a limited lifespan?

Why do solid-state drives even have a limited number of read/write cycles, usually 100,000-300,000 cycles? For hard-disk drives, it is understandable why they wear out. That is because they have ...
2 votes
5 answers
897 views

Way to measure delay propagation between two different systems

I have a system that sends data from one location to another via radio and I needed to find out the point to point delay propagation from the sensor measurement on one side to the reception on the ...
34 votes
7 answers
15k views

Can we not simply connect a battery to a RAM to prevent data loss during power cuts?

So, I was just wondering about how volatile memory storage loses data when the power to them is cut off. But can we not solve that problem by using a battery in conjunction with a RAM and a ROM and ...
0 votes
1 answer
50 views

Are there risks to running one computer with two completely different power sources? [closed]

I have experienced two computer power supplies using the same main power utility company here (same breaker, just different circuit). I am planning out an off-grid system, am considering running one ...
15 votes
5 answers
11k views

How to find socket for ThinkPad keyboard ribbon cable connector?

I am looking for a socket which is able to receive the connector of the ThinkPad X41's keyboard ribbon cable. How do I identify the socket so that I can find it on the (German) market? Background: I ...
23 votes
1 answer
4k views

How does the switch on the back of older computer power supplies work to vary between 110 and 220 volt input?

There is a little switch on the back of older computer power supplies to select between 110 and 220 volt AC input. I imagine this switch enables/disables a 220 to 110 volt transformer. Or perhaps a ...
2 votes
1 answer
502 views

What was the crysistor?

I'm reading through Jim Williams' "Analog Circuit Design: Art, Science and Personalities", and a mysterious component called a crysistor is mentioned. There are a few clues in the text, like the fact ...
0 votes
1 answer
781 views

Why does a flip-flop's outputs have to be the inverse of each other and an invalid/forbidden state discouraged [duplicate]

After reading, researching, and asking questions about flip-flops. My understanding is as follows: They are not the only means of storing state but are one of them. The circuit has been constructed ...
0 votes
2 answers
248 views

HDMI: Can a computer still detect a monitor properly if some of the TDMS pins/wires are damaged? [closed]

Can a faulty HDMI-cable with damaged TDMS pins/wires still work to the extent that the computer can still detect the monitor, but the monitor just will not display anything (except for no signal)?
1 vote
1 answer
210 views

A component has blown on my HP elite book 840 G6. I need help identifying it if it all possible

Here are the pictures. It was late and I shorted 2 pins of the smart card reader ribbon connector. Don't know how such a stupid mistake, but this component on the other side of the board went up and ...
0 votes
1 answer
79 views

I’m getting little more than 12 V in my computer PSU, should I use it?

I bought a refurbished computer ATX PSU, it had the most generic PCB I have ever witnessed. Seems like has a optocoupler and works with sdc2921 IC. In 12 V rail I’m getting 12.25 V. In 5 V I’m getting ...
2 votes
1 answer
3k views

Is A XNOR B logically equivalent to A XOR (NOT B)?

I am just wondering if its fair to say that A XNOR B is logically equivalent to A XOR ~B? If yes, how do I justify that without a truth table?
8 votes
8 answers
6k views

Can you base a computer around a 32-bit microcontroller?

We all have(mostly) 32-bit machines at our homes. But the 32-bit machines have a microprocessor in them. I was reading an article about the ARM Cortex. Its a 32-bit microcontroller. Now that intrigued ...
1 vote
1 answer
386 views

ESD Wrist Strap When Working on Monitors and Power Supply

My book for the A+ exam specifically says not to use ESD for repairing monitors or power supplies. Why is this? I understand that their capacitors hold lethal amounts of charges, but the motherboard ...
1 vote
1 answer
785 views

Looking for an explanation of grounding in relation to computers and DVI-HDMI adapters

I recently found that a DVI-HDMI adapter, purchased to connect the micro-HDMI port on my new Raspberry Pi 400 to the DVI port on my monitor, behaves strangely: it works well when connecting to my ATX ...

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