[HN Gopher] Hacker mods an M1 Mac mini to receive power over Eth...
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Hacker mods an M1 Mac mini to receive power over Ethernet instead
of AC
Author : nrsapt
Score : 124 points
Date : 2023-08-01 19:54 UTC (3 hours ago)
(HTM) web link (www.inferse.com)
(TXT) w3m dump (www.inferse.com)
| [deleted]
| bgentry wrote:
| The actual source referenced by the article appears to be this
| tweet thread:
| https://twitter.com/Merocle/status/1686093369322176512
| jeffbee wrote:
| This seems to simply ignore the max continuous power rating of
| 150W. The mini can output 15W on each thunderbolt port and
| another 15W on its two USB ports, which is already nearly the
| limit of 51W assured to each PoE++ endpoint, not even counting
| the mini's own requirements.
| JoeAltmaier wrote:
| PoE is a mature technology. Curious that laptops have not been on
| board.
| contingencies wrote:
| Historic energy consumption is probably higher than classically
| POE supported.
|
| Also, any length of POE run gets voltage drop, and POE switches
| and injectors often have tedious modal configuration based upon
| length of run and are designed with non-standard limitations
| such as maximum draw limits shared across multiple ports, which
| in aggregate will cause no end of issues. For verification, ask
| any experienced CCTV installer. These are exactly the sort of
| issues that cause users to take products back to their
| distributors.
|
| So it's a case of "works in theory, PITA in reality, probable
| support and brand image impact huge, resulting priority zero".
| JoeAltmaier wrote:
| It's really popular in factories etc, because it reduces
| cable runs I guess.
| clintonb wrote:
| An electrical outlet or USB-C connection is more readily
| available to me than an Ethernet port with POE. Laptops aren't
| onboard because the problem of powering laptops is largely
| solved. Also...not many laptops have Ethernet ports.
| asadhaider wrote:
| Site's getting hugged to death by HN possibly, cached link to
| article here-
| https://web.archive.org/web/20230801195510/https://www.infer...
| [deleted]
| hhh wrote:
| Merocle is also the creator of the Raspberry Pi Blade.
|
| https://www.kickstarter.com/projects/uptimelab/compute-blade
| disillusioned wrote:
| Having inadvertently plugged a 24v passive PoE live connection
| into an old 2012 Mac Mini and immediately frying it, this is
| welcome news!
| mmastrac wrote:
| I thought most modern devices had isolation!
| somat wrote:
| Note that there are real 48v 802.3af/at power over ethernet
| devices where the power source has to assert that the power
| drain wants the power before it powers up and fake "passive"
| 24v systems where the line is always energized. probably
| where the GP got the injector from.
|
| My personal involvement on this was several years ago when I
| was going to buy several unifi access points. It turns out
| you have to be careful because many of the models advertise
| as being POE but in reality are jank 24v passive systems. I
| have not kept up with the current unifi lineup but at the
| time you had to make sure to get the "AC Pro" to have real
| 802.3af compatibility.
| mmastrac wrote:
| I have a load of Unifi stuff here and it all supports
| active PoE, but works just fine with passive. The PoE
| outputs all autonegotiate.
| progbits wrote:
| Indeed, surprising.
|
| From IEEE 802.3 (revision 2012), section "32.6 PMA electrical
| specifications":
|
| > The PHY shall provide electrical isolation between the DTE
| or repeater circuits, including frame ground and all MDI
| leads.
|
| > This electrical separation shall withstand at least one of
| the following electrical strength tests: > [...]
|
| > b) 2250 Vdc for 60 s, [...]
|
| Non-compliant Ethernet PHY?
| evadne wrote:
| Passive PoE is always on
|
| Active PoE is negotiated with handshake
| jcrawfordor wrote:
| Yes, but passive PoE is almost universally at 24v, and
| per the Ethernet spec (as quoted above) an Ethernet PHY
| should tolerate 24v fine. This is important as transients
| from nearby lightning or occasionally even coupling to
| power cables can produce this kind of voltage. Ethernet
| connectors are magnetically coupled for protection from
| these transients.
|
| The problem with PPoE in these cases is, I think, not the
| voltage so much as the current. The continuous 24v supply
| may overheat the magnetic coupling transformer and cause
| it to fail. Some Ethernet interfaces, usually on telecom
| equipment and quality switches, have over current
| protection to prevent this. Unfortunately consumer
| devices usually don't.
|
| It's important to understand this because 802.3af etc.
| _does_ provide power without being asked - as a rest for
| a characteristic resistance on the receiver. Otherwise it
| wouldn 't know if a PoE-capable device was connected. Up
| to 20v can be applied during this process but it is time
| limited. In general, 802.3 PoE supplies must monitor the
| current usage of the powered device and cut off power if
| it is too high or even too low for more than a short
| period of time. This is in part to prevent this
| overheating problem on devices that might, for some
| coincidental reason, fall into the appropriate resistance
| range to activate PoE.
|
| In other words, 24v or even hundreds of volts for a few
| seconds is perfectly safe. 24v for minutes is likely to
| cause damage to devices without better protection than
| the spec requires. Old Ethernet equipment used to make
| the non-isolated components relatively easy to replace so
| that repairs after a problem like this were easier but
| now the isolation is a tiny surface mount part and
| replacing it will require tools and skill.
| wslh wrote:
| A few days ago I found "Charging My MacBook Air M1 with a
| Standard Mobile Phone USB Charger" [1]. PoE it is in similar
| ranges.
|
| [1] https://news.ycombinator.com/item?id=36893299
| mmastrac wrote:
| I use PoE extractors to power a few different devices in my
| house, including RPis and some non-PoE switches. It's
| ridiculously easy to use them, but you generally need to know the
| voltage you want ahead of time.
| EvanAnderson wrote:
| PoE splitters with USB outputs are really handy since
| "everything" plugs-in to USB now.
| poolopolopolo wrote:
| Holy moly, didnt know these things existed :O and fairly cheap
| as well, always though PoE a bit of useless since most devices
| dont support it and it was (is?) quite dangerous.
| mmastrac wrote:
| If you have modern PoE dispensing (?) equipment it's pretty
| safe as the devices all auto-negotiate.
| erwincoumans wrote:
| We powered the Mac Mini M1 using 12V DC, bypassing the built-in
| AC power adapter, and used it for some quadruped robot
| experiments. Some details on the connector are here:
| https://www.ifixit.com/Answers/View/574827/What+PSU+connecto...
| (that article mentions Mac Mini 2018 but the connector/pinout
| still works fine for Mac Mini M1)
| [deleted]
| metadat wrote:
| > Thanks to the power efficiency of Apple Silicon, the M1 Mac
| mini was the perfect hardware to test out PoE, as on idle, the
| device only consumes 6W. When some load is applied to the
| internals, that power draw can go up to 40W. After some thorough
| research, we found out that the maximum throughput of Power over
| Ethernet was 15.4W and that too over varying voltages, which are
| details that Ivan had left out when showing off his findings on
| Twitter.
|
| The last sentence has enough typos that I'm not able to follow
| what they're trying to say. What happens when the machine
| requires more than 15.4W? If the thing isn't actually usable or
| stable in real-world scenarios, this becomes a lot less exciting.
|
| It'd also be more interesting if the full components list of what
| was added to the inside of the machine to make this possible was
| shared.
|
| Edit: Thanks to @ravetcofx for revealing how more power can be
| delivered over PoE https://news.ycombinator.com/item?id=36962808
| lights0123 wrote:
| The article simply assumes that the creator only supports the
| original POE when they say "POE". There's a good chance they
| used a PoE+ or PoE++ adapter that supports more wattage.
| tredre3 wrote:
| There are more details in the twitter thread, including a table
| of PoE standards:
|
| https://twitter.com/Merocle/status/1686093369322176512
|
| > What happens when the machine requires more than 15.4W?
|
| The voltage will sag and the machine will likely crash!
| ravetcofx wrote:
| " the M1 Mac mini was the perfect hardware to test out PoE, as on
| idle, the device only consumes 6W. When some load is applied to
| the internals, that power draw can go up to 40W. After some
| thorough research, we found out that the maximum throughput of
| Power over Ethernet was 15.4W "
|
| They'll have to bump it up to 802.3bt (Poe ++) which can support
| 60W.
|
| Cool Project though, I've been wanting to mod my Mac Mini m1 to
| run off USB-C PD which should be possible with modification
| because it uses the same PD IC as the Macbooks (CD3217) which
| could mean I could get it to eventually run off of a battery pack
| rfgmendoza wrote:
| i would actually like being able to power my mac mini with just
| a usb-c dock like a macbook
| dheera wrote:
| I'm very skeptical of PoE now after 3 PoE adapters killed 3
| Raspberry Pis I have.
|
| I wouldn't want to risk something more expensive to that shit.
|
| At this point I'd rather just have straight up 19V + and -
| cables bundled together with the Ethernet with some heatshrink
| around the whole thing to make it look like 1 cable.
| CameronNemo wrote:
| You sure you want to blame poe as a whole instead of the RPI
| hat?
| haswell wrote:
| PoE is used extensively in network deployments involving
| rather expensive hardware.
|
| I understand the instinct to avoid it at this point, but I'm
| curious what happened in your case because I've never
| experienced issues.
|
| I did work somewhere where someone fried equipment by
| incorrectly terminating a batch of Ethernet cables thereby
| sending voltage to the wrong place.
| bitbckt wrote:
| Minor correction: 802.3bt added 51W (Type 3) or 71W (Type 4).
| 60W isn't a standard power level. Some switches support up to
| 95W per port with PoH.
| OJFord wrote:
| Surely they're all ' _up to_ '? It's not 'you must sink this
| much current or else not compliant'?
|
| It seems like a weird thing for TFA to say anyway - my PoE[+]
| switch was the cheapest 8 port I could get a few years ago on
| Amazon, and does 30W per port. I don't really understand how
| you could look into it at all, be willing to attempt the
| hack, but not use a switch (or injector or whatever) that's
| capable of powering it under load.
| bitbckt wrote:
| Hah, yes they are all 'up to' on the device side. A switch
| port or injector is not compliant with a particular
| standard if it does not provide for the type-specific load,
| however.
| r00fus wrote:
| What's the goal of having a MacMini running off an external
| battery? I mean, it seems less cost effective than just getting
| a MB Air and not using the screen...
| tyingq wrote:
| That it happens to be 12 volts DC has some value versus
| whatever power loss an inverter has for use in a vehicle.
| Though I'm with you on the relative ease of starting with a
| laptop instead.
| lapetitejort wrote:
| The goal of most of these projects are usually to demonstrate
| that they're possible. Actual use cases are left as an
| exercise for the reader.
| Dalewyn wrote:
| The scientists were too busy asking if they could, because
| it's not their job to ask if they should.
| simlevesque wrote:
| > it seems less cost effective than just getting a MB Air and
| not using the screen...
|
| how ? why would paying for a screen and not use it be cheaper
| ?
| arcticbull wrote:
| Economy of scale, mostly.
| SmellTheGlove wrote:
| No idea, but if they got it running on USB PD, battery pack
| aside, it would make it a one cable connection to a monitor
| that has PD support. Multiple cords don't actually bother me
| but it sounds kinda neat.
|
| Anyhow I guess the goal is "because you can"
| dylan604 wrote:
| This would be fun for when LEOs come in to take your
| computer, they can easily keep it powered so all of the
| decrypted keys stay in memory. Killing power means going back
| to an encrypted state. In high profile cases for desktops,
| there's techniques for splicing the power cable to switch to
| a battery pack. This would make it much easier for the
| unskilled LEO to take your shit. Cause we all know you're the
| one their after. Sleep tight! ;-)
| bravetraveler wrote:
| Avoiding the inevitable spicy pillow seems like a good reason
|
| An external/easily replaceable battery would be excellent
| come time to deal with cell age
| bravetraveler wrote:
| Does this read like an attack against Apple laptops
| specifically, or something? Already -2 five minutes after
| posting it.
|
| Leaving as-is for feedback. I don't get the controversy. I
| could've been a jerk and said just buy a UPS - this is an
| established concept.
|
| Edit: thank you kind souls for restoring the imbalance -
| carry on :D
| poolopolopolo wrote:
| cheaper and bigger batteries? always replaceable in the
| future? And tbh laptop batteries are not meant to be used
| 24/7, personally would avoid it.
| OJFord wrote:
| I could see it making sense in a 'van life' context to use a
| smaller local battery rather than plug everything in to your
| main leisure battery. Use the latter to charge Makita packs
| say and then run most other stuff off those (there's a decent
| amount of open 3D printable adapters for them, as well as
| third-party/AliExpress stuff).
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