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Comment by castratikron | Hacker News Reader

Oh, man. I'm surprised that card works at all with that wiring. High speed single ended signaling does not do well off-board. Have you done any kind of integrity testing, like writing a GB to the disk and then reading the checksum?

If anyone is looking to do this mod, at least consider using a shielded ribbon cable like so:

https://www.amazon.com/LANMU-Extension-Flexible-Monoprice-Ra...

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Data transfers in SD cards are CRC checked.

In addition, the card will by default start in a 12.5MB/s mode at 3.3v, which is 25MHz per lane. That's not DC, but it's definitely slow enough to run on some pretty dodgy wiring. It will only switch to higher speed modes if requested, and if it actually works (falling back to lower speeds otherwise).

SD cards typical aren't run on a very high speed bus. A couple of MHz is pretty typical and this sort of wiring is no problem at those speeds.

Definitely no need for a shielded cable either.

Was going to say, I’ve run the stuff with whatever bits of cat5 cable I had on my desk, they’re not that fussy.

They're not that fussy at low speeds. You will have problems getting UHS cards to run at full speed.

That’s not shielded. I doubt it offers any more signal integrity than the 30awg wires nicely taped together.

And the 30awg wires can go around corners without folding.

I have an FFC version of that product and it works very well. Whatever data rate reduction I might see from the additional length is overtaken in a really big way by my ability to use full-size SD cards instead of the micro-SD card slots my development boards usually come with.

You definitely don't need a shielded cable. SD is very robust. Hell, I've seen people run SPI or I2C over similar lengths and types of cable and those two protocols are much less robust than SD.

Hi, I'm the author of this hack---the card works at 50 MHz with no errors.

I can't understand the negative sentiment in these replies. A ribbon cable is objectively a better design choice. If someone is attempting this mod themselves why would they not pick the best choice? We're all engineers, here, right? Do you all prefer to drive without wearing a seat belt as well?

I think people were more put off by your amazement that it worked at all (and the "tone" which went with it), when there is no reason for it considering the original write-up has no issues with its implementation. Of course use what makes your project work the best, but don't go monster cable level on parts that need not.

It's a better choice only if don't consider the cost or other factors. Engineering isn't about reaching a theoretical ideal "best", engineering is a about a practical compromise, getting things done.

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