New Sandisk Pro 256GB(200MB/s) performing worst than old 128GB(170MB/s)?

[Lex-]

On a Canon Eos M Crop mood version of August 2023.

I get Green time and stable continuous recording on my old 128GB (which is up 170MB) but not on any of the two SD cards of 256GB (that goes up to 200MB) which keep interrupting every few seconds, specially if there is a lot of bright light.

- SanDisk Extreme PRO -  SDXC 128 GB, up to 170 MB/s, UHS-I, Class 10, U3, V30

- SanDisk 256GB Extreme PRO, , SDXC, up to 200 MB/s, + RescuePro Deluxe, UHS-I Class 10 U3 V30

the ones of 256GB re supposed to be better because are up to 200MBs instead of only 170mbs that the 128GB shows... but is happening the opposite, I don't understand, the features are the same in all (Followed Sergio Russo advice in Youtube)

 when filming in 4.2k, the 128GB are eaten pretty fast and the 256GB just stop recording too often.

Can any one give clarity on why? What should I do? Aren't this ones supposed to be the recommended ones?

[Walter Schulz]

Here is our chart of compatible cards: https://wiki.magiclantern.fm/cards_240mhz

There may be some assumptions with cards not being backed by experience ...

1) Numbers "170 MB/s" and "200 MB/s" are for read only.

2) In "old times" (= before Bilal's update to SD_UHS.mo) there were two cards earning a recommendation:
Sandisk Extreme Pro 95 MB/s and Sandisk Extreme Pro 170 MB/s. Those days are gone.
For today: I don't know where and/or who said the newer Extreme Pro 256 GB (specified R200/W140) is a better performer. Instead we failed to see improvement in performance.
Bilal came up with an explanation in our Discord https://discord.com/channels/671072748985909258/844581352082898975/1252388053150859335

My current guess for the first section of your question:

Because DIGIC 5 is lacking Tuning command, and according to SD Association in "PartA2_SD Host_Controller_Simplified_Specification_Ver3.00.pdf":

 "Tuning is always required to operate SDR104", and for SDR50 it's optional.

by default if Tuning command is not used, SD host controller will use fixed tuning value, and this might work fine for some SD cards and host controllers and might not work for others . . 

You may want to test "Access Mode SDR50" with Sandisk R200/W140. Setting is located in Overclocking sub menu.

PS: In cardreaders without overclocking (= pure UHS-I) older 170 MB/s performs slightly better than R200/W140. Difference is marginal: Just 1 MByte/s. See https://cameramemoryspeed.com