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by jancsika 980 days ago
> Here's an example of a USFF (ultra small form factor) for $110 - https://www.ebay.com/itm/325826958401

Hm...

> No adapter is included. Needs 65W or above (most dell/hp laptops around the year it came out are compatible)

The 65W power adapter on Dell retails for $46.99 on sale, bringing the grand total to $156.99.

And that's just after skimming your link for 2 minutes.
3 comments
ammar2 980 days ago
You don't need to buy the OEM power adapter for $46.99

The great thing about these Optiplexes is that they use a standard 20v 4.5x3mm DC jack for power. I run mine off a UPS with a usb-c to barrel jack cable.

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dpedu 980 days ago
No they don't. It is a barrel jack you can obtain an adapter for elsewhere, but your adapter is going to be missing the third pin. This type of system uses the 3rd line to communicate with the power supply and during startup the computer asks it how much power it is capable of supplying. If the power supply doesn't answer, it drastically throttles your CPU. Sure, you can boot the system, though it would be throwing away the majority of your cpu performance.

Furthermore, I have several of these systems and tried sourcing 3rd party power adapters online. For this aspect, not one of them worked correctly.

I did a write up here: https://old.reddit.com/r/homelab/comments/11o0x5o/dell_3050_...

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ammar2 980 days ago
Oh huh maybe I've been running mine in the throttled mode unknowingly, thanks for the pointer.

Edit:

I ran the `cpufreq-info` command in your write-up and it gave me the correct:

> hardware limits: 800 MHz - 3.00 GHz

Maybe it's because the usb-c to barrel jack cable I picked up was marketed for dell laptops?

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gsich 980 days ago
Lenovo uses a resistor to check the PSU power, should be easy enough. Don't know what Dell is doing.
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ammar2 980 days ago
Looks like a one-wire protocol talking to a DS2501 chip

https://hclxing.wordpress.com/2014/02/09/hacking-a-dell-powe...

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yftsui 980 days ago
The author got almost everything correct except some minor parts. Using his charger as an example, it can be broken down as: DELL 00 AC090 195 046 CN09T2157161543835EAL 03 .

046 is the output current 4.6A instead of his partitioned as 46(there are power supplies output more than 10 amps).

The 22 bytes is the Dell PPID, which should be also present on the charger's label or the box: CN: Manufactured in China, some of them are TH which means made in Thailand. 09T215: Dell Part Number. 71615: Manufacturing factory code. 438: 2004 or 2014, March, 8th (Dell use YMD 3 bytes thus it is a lossy conversion always). 35EAL: This should be the serial number.

The last part 03 is a CRC16 (x16 + x15 + x2 + 1) checksum.

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0cf8612b2e1e 980 days ago
Initial costs are higher with a SFF. Your use case dictates if it is worthwhile.

Last I checked, a Pi also does not come with a charger, case, or storage.

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nl 980 days ago
Just shop around a bit.

Ebay Australia has a Lenovo M700 i5 with 8GB RAM, 256 GB SSD for AU$135.00 (US$86) including power supply and cords.

https://www.ebay.com.au/itm/126118210243

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