6 ms·

HDMI provides power - that's how old chromecasts can work without a separate power plug. The comment about NPNs and PNPs is garbage, but there is a design faul

HDMI provides power - that's how old chromecasts can work without a separate power plug. The comment about NPNs and PNPs is garbage, but there is a design fault with the board - it shouldn't allow HDMI power to flow backwards into the motherboard when the motherboard shuts off. That would likely cause a power rail sequencing issue on the board or SSD, leading to latch-up of various ICs, and non-detection on the SSD on the flowing bootup

LeifCarrotson 2y ago
And by "the board" I trust you mean the MSI PRO X670-P WIFI motherboard. There's nothing incorrect about the behavior of the SSD when it's being operated outside the prescribed voltage and power thresholds. If there's a trickle (and to be clear, the 5V at 300 mA available from an HDMI cable is a trickle for a full motherboard) of current into the 3V3 bus on the ATX connector, something will be the very lowest PMIC to turn on. It's just that on this system, the SSD was the first thing. If anything, the SSD will probably be highly tolerant of brownouts because its LDO will run at around 1.9V.
- hulitu 2y ago
  > There's nothing incorrect about the behavior of the SSD when it's being operated outside the prescribed voltage and power thresholds. It shall set itself in Reset state.
  - LeifCarrotson 2y ago
    That would be nice, in practice, the SSD requires its power rails to start up in a particular sequence and with very particular voltages.
  - shadowpho 2y ago
    Only few devices are actually able to do that. Vast majority require require proper voltage sequencing, because to do otherwise is to add cost to your IC
- Dylan16807 2y ago
  > There's nothing incorrect about the behavior of the SSD when it's being operated outside the prescribed voltage and power thresholds. I'd put some more emphasis on "when", though. If it never comes back when power comes back that's not particularly correct.
  - crest 2y ago
    That's because if this theory is correct from the point of view of the SSD there was no reboot yet, because there was never any total power loss.
    - Dylan16807 2y ago
      It handles warm reboots without power loss just fine, so it deciding now it needs to wait for power loss seems like a flaw.
      - wtallis 2y ago
        If the SSD reacts to the start of a brown-out with supply voltage dropping way below spec as a signal that an unplanned power loss is happening, then it may do an emergency flush and shutdown that leaves it simply waiting for power to finish dropping to zero. It makes at least some sense for the drive to not try to wake up from that state without a clean power cycle.
        Dylan16807 2y ago
        I think "makes at least some sense" and "not particularly correct" can be true at the same time.
    - smileybarry 2y ago
      It should still handle PCIe probing and (logical) reconnection without a reboot, though, e.g.: PCIe redirection for a VM.
magic_smoke_ee 2y ago
The reality is retail PC electronics, like much consumer electronics with short lifespans, are designed/engineered and manufactured more-or-less like disposable e-waste garbage. Eevblog Dave or Bigclive might be able to get to the bottom of the circuit or manufacturing design error, albeit with some help if it turns out to be a digital-or-up-the-stack issue.
- KeplerBoy 2y ago
  meh, I rarely have electronics fail these days. Whatever corners designers are cutting seem perfectly adequate to be cut to make stuff affordable.
  - lazide 2y ago
    The rise of mass produced cheap ICs with somewhat reasonable behavior are the cause. It’s cheap to add some logic to something when you’re making a million or more of them, than when it’s an additional couple discrete components and an additional circuit you need to add yourself.
gbil 2y ago
>HDMI provides power - that's how old chromecasts can work without a separate power plug. I still have the first Chromecast released, it doesn't operate without external power plugged in so I'm not sure about the validity of your comment, at least for the chromecast part
- bradfitz 2y ago
  https://www.hdmi.org/spec21sub/cablepower https://www.hdmi.org/spec21sub/cablepower
  - rzzzt 2y ago
    Connection is the same as attaching an ordinary, "wired" HDMI Cable, except that active cables can only be attached in one direction: One end of the cable is specifically labeled for attachment to the HDMI Source (transmitting) device, and the other end of the cable must be attached to the HDMI Sink (receiving) device. If the cable is attached in reverse, no damage will occur, but the connection will not work. HDMI Cables with HDMI Cable Power include a separate power connector for use with source devices that do not support the HDMI Cable Power feature. This is not your run-of-the-mill HDMI cable for sure.
  - numpad0 2y ago
    No, not that feature. HDMI supported 5V/55mA power out for years. It's meant for EDID ROM chips and maybe HDMI selectors too, not Linux based computers, but some TVs could take it in gross violation of specifications and its spirits.
- nosrepa 2y ago
  And the serial number of that power plug is MST3K-US
- kuschku 2y ago
  The first chromecast actually operated without external power, but it only worked with some TVs. It's possible yours didn't provide enough power via HDMI, but at least ours worked just fine.
ssl-3 2y ago
HDMI does provide power, but this is not how Chromecast (or similar) devices have ever been powered. It supplies 5v at up to 50mA from a sink device like a TV. That's only a quarter of a Watt, which is perhaps enough for something like an EDID ROM, or maybe a switch or perhaps an extender. It is not enough power to run a Chromecast. HDMI 2.1b Amendment 1 [0] can supply up to 300mA at 5v, but that specification is only a year or so old. It requires a special cable. And 1.5 Watts maximum isn't enough to run a Chromecast, either. (The intent is to be able to use it to run a somewhat thirstier extender than the earlier specifications would permit.) 0: https://www.hdmi.org/spec21sub/cablepower https://www.hdmi.org/spec21sub/cablepower
- kalleboo 2y ago
  > It supplies 5v at up to 50mA from a sink device like a TV. And USB is also only supposed to supply 100 mA until the device negotiates for more. But literally every device in the real-world just wires the port to the 5V rail with 2 A overcurrent protection and your "dumb" USB-powered fan gadget can draw as much as it wants without any negotiation. I can totally see TVs doing the same
  - indrora 2y ago
    > But literally every device in the real-world just wires the port to the 5V rail with 2 A overcurrent protection Not quite. To be USB Compliant, you have to do some work here and there. There's about six different options. The most common is overcurrent detection, such as is seen in [1]. There is a whole specification built by USB-IF on how to handle higher current ("battery charge") situations, spurred by apple [2], with all sorts of weird corner cases [3]. Now, USB-C changes that and specifically calls out that a "compliant" downstream device has to negotiate USB PD or declare yourself a USB-2.0 type-C device. [4] It's not uncommon for newer devices that conform strictly to the USB4 specification to not even power a port that hasn't negotiated USB-PD or Legacy PD -- if you encounter devices that get weird when powered via a usb-c to usb-c cable but work fine on a usb a-to-c cable, you've seen someone skimp out on $0.00001 in resistors. [1] https://www.microchip.com/en-us/development-tool/EVB-USB2514B-FS https://www.microchip.com/en-us/development-tool/EVB-USB2514... [2] https://www.usb.org/document-library/battery-charging-v12-spec-and-adopters-agreement https://www.usb.org/document-library/battery-charging-v12-sp... [3] https://www.graniteriverlabs.com/en-us/technical-blog/usb-battery-charging-1-2-testing-introduction https://www.graniteriverlabs.com/en-us/technical-blog/usb-ba... [4] https://community.infineon.com/t5/Knowledge-Base-Articles/Termination-Resistors-for-Type-C-to-Legacy-Ports/ta-p/256004# https://community.infineon.com/t5/Knowledge-Base-Articles/Te....
0xTJ 2y ago
The HDMI source, not the HDMI sink, provides the power at 5 V. As far as I know, every Chromecast required an external power connection.
globnomulous 2y ago
My office stereo has physical connections between the following devices (simplifying a bit) - Speakers connect via speaker wire to monoprice 7x200 amp - Monoprice amp connects via RCA to denon x3800h - X3800h receives HDMI from desktop computer and sends HDMI to a monitor. - Same computer connects via Displayport to the same monitor I used to hear an infuriating buzz when my 2080TI started to work hard. It changed depending on the screen output, GPU strain, and mouse activity but was constant. It acted like a combination ground loop cum coil whine. The first fix I discovered was to ground my monoprice amp to the 2080 TI PCB by wrapping one end of the exposed-copper (12 awg, I think) grounding wire through and around one of the holes in the board and attaching the other end to the Monoprice amp's grounding pin. This fixed the issue completely. Then I realized I could fix the issue more elegantly and elminate the need for grounding: I removed the grounding wire and replaced my normal HDMI and Displayport cables with fiber optic HDMI and Displayport cables. The buzz has never recurred. I've never delved further into the problem, but my conclusion is the same as yours: there's a design fault somewhere on the board, which is causing electricity to flow in ways it shouldn't. I'm using an MSI z690 ddr4 edge wifi board. Same brand, same generation, as the board where this guy is having his SSD power issue. I still hear a weird, loud buzz through the stereo (including a separate amp and separate pair of speakers) when my partner runs her hair dryer upstairs, even though my stereo runs on its own separate circuit, so regardless of the design issues in the board, there's definitely also an issue in my electrical system.
- transpute 2y ago
  Power conditioner can improve AC isolation https://www.amazon.com/Furman-AC-215A-Conditioner-Auto-Resetting-Protection/dp/B003PJ6NPO/ https://www.amazon.com/Furman-AC-215A-Conditioner-Auto-Reset... https://surgestop.com/surge-products/m-474.html https://surgestop.com/surge-products/m-474.html
  - globnomulous 2y ago
    Thanks, this is great advice. I'm using two SurgeX SX 2120-SEQ power conditioner+sequencers -- one for the desktop devices and one for the stereo. I'm baffled that, even with the conditioners and even though I'm a separate circuit in my office, the hairdryer is still able to do something to affect the electricity in my office.

LeifCarrotson 2y ago

And by "the board" I trust you mean the MSI PRO X670-P WIFI motherboard. There's nothing incorrect about the behavior of the SSD when it's being operated outside the prescribed voltage and power thresholds. If there's a trickle (and to be clear, the 5V at 300 mA available from an HDMI cable is a trickle for a full motherboard) of current into the 3V3 bus on the ATX connector, something will be the very lowest PMIC to turn on. It's just that on this system, the SSD was the first thing. If anything, the SSD will probably be highly tolerant of brownouts because its LDO will run at around 1.9V.

hulitu 2y ago
> There's nothing incorrect about the behavior of the SSD when it's being operated outside the prescribed voltage and power thresholds. It shall set itself in Reset state.
- LeifCarrotson 2y ago
  That would be nice, in practice, the SSD requires its power rails to start up in a particular sequence and with very particular voltages.
- shadowpho 2y ago
  Only few devices are actually able to do that. Vast majority require require proper voltage sequencing, because to do otherwise is to add cost to your IC
Dylan16807 2y ago
> There's nothing incorrect about the behavior of the SSD when it's being operated outside the prescribed voltage and power thresholds. I'd put some more emphasis on "when", though. If it never comes back when power comes back that's not particularly correct.
- crest 2y ago
  That's because if this theory is correct from the point of view of the SSD there was no reboot yet, because there was never any total power loss.
  - Dylan16807 2y ago
    It handles warm reboots without power loss just fine, so it deciding now it needs to wait for power loss seems like a flaw.
    - wtallis 2y ago
      If the SSD reacts to the start of a brown-out with supply voltage dropping way below spec as a signal that an unplanned power loss is happening, then it may do an emergency flush and shutdown that leaves it simply waiting for power to finish dropping to zero. It makes at least some sense for the drive to not try to wake up from that state without a clean power cycle.
      - Dylan16807 2y ago
        I think "makes at least some sense" and "not particularly correct" can be true at the same time.
  - smileybarry 2y ago
    It should still handle PCIe probing and (logical) reconnection without a reboot, though, e.g.: PCIe redirection for a VM.

magic_smoke_ee 2y ago

The reality is retail PC electronics, like much consumer electronics with short lifespans, are designed/engineered and manufactured more-or-less like disposable e-waste garbage. Eevblog Dave or Bigclive might be able to get to the bottom of the circuit or manufacturing design error, albeit with some help if it turns out to be a digital-or-up-the-stack issue.

KeplerBoy 2y ago
meh, I rarely have electronics fail these days. Whatever corners designers are cutting seem perfectly adequate to be cut to make stuff affordable.
- lazide 2y ago
  The rise of mass produced cheap ICs with somewhat reasonable behavior are the cause. It’s cheap to add some logic to something when you’re making a million or more of them, than when it’s an additional couple discrete components and an additional circuit you need to add yourself.

gbil 2y ago

>HDMI provides power - that's how old chromecasts can work without a separate power plug. I still have the first Chromecast released, it doesn't operate without external power plugged in so I'm not sure about the validity of your comment, at least for the chromecast part

bradfitz 2y ago
https://www.hdmi.org/spec21sub/cablepower https://www.hdmi.org/spec21sub/cablepower
- rzzzt 2y ago
  Connection is the same as attaching an ordinary, "wired" HDMI Cable, except that active cables can only be attached in one direction: One end of the cable is specifically labeled for attachment to the HDMI Source (transmitting) device, and the other end of the cable must be attached to the HDMI Sink (receiving) device. If the cable is attached in reverse, no damage will occur, but the connection will not work. HDMI Cables with HDMI Cable Power include a separate power connector for use with source devices that do not support the HDMI Cable Power feature. This is not your run-of-the-mill HDMI cable for sure.
- numpad0 2y ago
  No, not that feature. HDMI supported 5V/55mA power out for years. It's meant for EDID ROM chips and maybe HDMI selectors too, not Linux based computers, but some TVs could take it in gross violation of specifications and its spirits.
nosrepa 2y ago
And the serial number of that power plug is MST3K-US
kuschku 2y ago
The first chromecast actually operated without external power, but it only worked with some TVs. It's possible yours didn't provide enough power via HDMI, but at least ours worked just fine.

ssl-3 2y ago

HDMI does provide power, but this is not how Chromecast (or similar) devices have ever been powered. It supplies 5v at up to 50mA from a sink device like a TV. That's only a quarter of a Watt, which is perhaps enough for something like an EDID ROM, or maybe a switch or perhaps an extender. It is not enough power to run a Chromecast. HDMI 2.1b Amendment 1 [0] can supply up to 300mA at 5v, but that specification is only a year or so old. It requires a special cable. And 1.5 Watts maximum isn't enough to run a Chromecast, either. (The intent is to be able to use it to run a somewhat thirstier extender than the earlier specifications would permit.) 0: https://www.hdmi.org/spec21sub/cablepower https://www.hdmi.org/spec21sub/cablepower

kalleboo 2y ago
> It supplies 5v at up to 50mA from a sink device like a TV. And USB is also only supposed to supply 100 mA until the device negotiates for more. But literally every device in the real-world just wires the port to the 5V rail with 2 A overcurrent protection and your "dumb" USB-powered fan gadget can draw as much as it wants without any negotiation. I can totally see TVs doing the same
- indrora 2y ago
  > But literally every device in the real-world just wires the port to the 5V rail with 2 A overcurrent protection Not quite. To be USB Compliant, you have to do some work here and there. There's about six different options. The most common is overcurrent detection, such as is seen in [1]. There is a whole specification built by USB-IF on how to handle higher current ("battery charge") situations, spurred by apple [2], with all sorts of weird corner cases [3]. Now, USB-C changes that and specifically calls out that a "compliant" downstream device has to negotiate USB PD or declare yourself a USB-2.0 type-C device. [4] It's not uncommon for newer devices that conform strictly to the USB4 specification to not even power a port that hasn't negotiated USB-PD or Legacy PD -- if you encounter devices that get weird when powered via a usb-c to usb-c cable but work fine on a usb a-to-c cable, you've seen someone skimp out on $0.00001 in resistors. [1] https://www.microchip.com/en-us/development-tool/EVB-USB2514B-FS https://www.microchip.com/en-us/development-tool/EVB-USB2514... [2] https://www.usb.org/document-library/battery-charging-v12-spec-and-adopters-agreement https://www.usb.org/document-library/battery-charging-v12-sp... [3] https://www.graniteriverlabs.com/en-us/technical-blog/usb-battery-charging-1-2-testing-introduction https://www.graniteriverlabs.com/en-us/technical-blog/usb-ba... [4] https://community.infineon.com/t5/Knowledge-Base-Articles/Termination-Resistors-for-Type-C-to-Legacy-Ports/ta-p/256004# https://community.infineon.com/t5/Knowledge-Base-Articles/Te....

0xTJ 2y ago

The HDMI source, not the HDMI sink, provides the power at 5 V. As far as I know, every Chromecast required an external power connection.

globnomulous 2y ago

My office stereo has physical connections between the following devices (simplifying a bit) - Speakers connect via speaker wire to monoprice 7x200 amp - Monoprice amp connects via RCA to denon x3800h - X3800h receives HDMI from desktop computer and sends HDMI to a monitor. - Same computer connects via Displayport to the same monitor I used to hear an infuriating buzz when my 2080TI started to work hard. It changed depending on the screen output, GPU strain, and mouse activity but was constant. It acted like a combination ground loop cum coil whine. The first fix I discovered was to ground my monoprice amp to the 2080 TI PCB by wrapping one end of the exposed-copper (12 awg, I think) grounding wire through and around one of the holes in the board and attaching the other end to the Monoprice amp's grounding pin. This fixed the issue completely. Then I realized I could fix the issue more elegantly and elminate the need for grounding: I removed the grounding wire and replaced my normal HDMI and Displayport cables with fiber optic HDMI and Displayport cables. The buzz has never recurred. I've never delved further into the problem, but my conclusion is the same as yours: there's a design fault somewhere on the board, which is causing electricity to flow in ways it shouldn't. I'm using an MSI z690 ddr4 edge wifi board. Same brand, same generation, as the board where this guy is having his SSD power issue. I still hear a weird, loud buzz through the stereo (including a separate amp and separate pair of speakers) when my partner runs her hair dryer upstairs, even though my stereo runs on its own separate circuit, so regardless of the design issues in the board, there's definitely also an issue in my electrical system.

transpute 2y ago
Power conditioner can improve AC isolation https://www.amazon.com/Furman-AC-215A-Conditioner-Auto-Resetting-Protection/dp/B003PJ6NPO/ https://www.amazon.com/Furman-AC-215A-Conditioner-Auto-Reset... https://surgestop.com/surge-products/m-474.html https://surgestop.com/surge-products/m-474.html
- globnomulous 2y ago
  Thanks, this is great advice. I'm using two SurgeX SX 2120-SEQ power conditioner+sequencers -- one for the desktop devices and one for the stereo. I'm baffled that, even with the conditioners and even though I'm a separate circuit in my office, the hairdryer is still able to do something to affect the electricity in my office.