Re: 2017-06-20-netbsd-raspi-earmv6hf.img

[Mark Millard <markmi%dsl-only.net@localhost>]

On 2017-Jun-24, at 11:23 PM, Michael van Elst <mlelstv%serpens.de@localhost> wrote:

> john%ziaspace.com@localhost (John Klos) writes:
> 
>> We know that SDR50 mode works with many, perhaps most, cards under NetBSD. 
> 
> SDR25 is a UHS mode (50MHz, 25MByte/s) and is specified for 1.8V signaling.
> The pi however can only do 3.3V signaling.
> 
> SDR50 is a UHS mode (100MHz, 50MByte/s) and is specified for 1.8V signaling.
> The pi however can only do 3.3V signaling.
> 
> HS is a pre-UHS mode and is specified for 3.3V signaling, the pi supports it
> for up to 50MHz (25MByte/s). This is performance-wise like SDR25.
> 
> Maybe you can get some combination of pi+card to work with 100MHz
> and 3.3V signaling. But that's out of spec.

That matches with what I found and reported
about the terminology.

I expect that I found what is being referred to as
"SDR50" when folks assert notably more than 25
MiByte/s (sequential): actually a way of
overclocking the rpi3's or rpi2's interface (still
at 3.3V so not SDR50):

https://www.jeffgeerling.com/blog/2016/how-overclock-microsd-card-reader-on-raspberry-pi-3

The author is very careful to report:

overclocking the microSD reader can cause
data corruption

He also reports that he treats is RPI's as
"cattle, not pets".

The overclocking involves providing a file:

/boot/config.txt

with specific text in it: a so called "dtoverlay
directive".

(Of course that is for the standard rpi
software.)


===
Mark Millard
markmi at dsl-only.net