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Question Speed shown on Sandisk (and other brands) of SD memory cards

wpshooter

Golden Member
Mar 9, 2004
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1) Are the speed ratings shown on Sandisk (and other brands) of SD memory cards the READ speed or the WRITE speed of the card or is the speed shown both the same for read and write functions ?

2) Are the speed ratings shown on the card its maximum or minimum speed(s) ?

3) Are SD cards backward compatible, i.e. if you have say a 120mb/s rated card and that is its maximum write speed, will a device that is only capable of writing at say 50mb/s function correctly with that SD card ?

Thanks.
 

VirtualLarry

No Lifer
Aug 25, 2001
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I'll take a shot.

1) Are the speed ratings shown on Sandisk (and other brands) of SD memory cards the READ speed or the WRITE speed of the card or is the speed shown both the same for read and write functions ?
Usually READ is way faster than WRITE. If they say, "Speeds up to 200MB/sec", they generally mean seq. read, under optimal (read: lab) conditions. You're results may be way below the rated speeds.

2) Are the speed ratings shown on the card its maximum or minimum speed(s) ?
Some of those speed ratings, for example class, U- , and A- ratings, I believe are actually the minimum WRITE speed sustainable, given the correct (read, new enough) reader / writer.

3) Are SD cards backward compatible, i.e. if you have say a 120mb/s rated card and that is its maximum write speed, will a device that is only capable of writing at say 50mb/s function correctly with that SD card ?
Depends if the reader supports the technology spec. For example, I don't think an SDXC card will work in an SDHC reader / writer. (There may be a firmware upgrade for the writer.)
 

StrangerGuy

Diamond Member
May 9, 2004
8,443
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This is my 512GB Samsung Evo plus mSD card on a USB3 reader:

Samsung Evo Plus 512GB.PNG

At QD1 4K, reads are 1/4 and writes are 1/43 versus a mediocre SATA SSD which explains why memory cards feels so slow despite their rated peak speeds.

From my testing, actual write speeds in all categories for USB sticks/cards can range from half to just 10% of their actual write speeds.
 

wpshooter

Golden Member
Mar 9, 2004
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A followup question.

If an SD card is placed in say a hunting trail camera for the recording of video data, which device (the trail camera or the SD card) contains the "data controller" which determines the flow speed, etc. of the data going from the camera to the SD card, when the trail camera is recording a video onto the SD card ? In other words, does an SD card have a "controller" on it, similar to a convention/old style mechanical computer hard drive or is the flow of data to the SD card strictly the job/function of the hardware in the trail camera ?

What I am ultimately trying to determine is WHY a trail camera would function fine when using a 90mb/s SD card but would NOT work with 100% (give bad file errors and lockup, in that, its menus would not function correctly and it can neither be turned on or off at times), when using a FASTER speed / 120mb/s SD card is placed in the camera.

Nothing wrong with the SD card because it functions fine on my desktop and laptop computers.

Thanks.
 

dlerious

Senior member
Mar 4, 2004
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What I am ultimately trying to determine is WHY a trail camera would function fine when using a 90mb/s SD card but would NOT work with 100% (give bad file errors and lockup, in that, its menus would not function correctly and it can neither be turned on or off at times), when using a FASTER speed / 120mb/s SD card is placed in the camera.

Nothing wrong with the SD card because it functions fine on my desktop and laptop computers.
How's the card formatted? Some of my devices require exFAT and I've had a few that were picky - had to format the card with the device. I look for the class rating on cards rather than listed speeds, usually U3 or V30 (or higher) for video. Like Larry mentioned, the U,C, and V ratings are minimum speeds, while speeds like 90 or 120 mb are maximum.
 

VirtualLarry

No Lifer
Aug 25, 2001
51,051
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What I am ultimately trying to determine is WHY a trail camera would function fine when using a 90mb/s SD card but would NOT work with 100% (give bad file errors and lockup, in that, its menus would not function correctly and it can neither be turned on or off at times), when using a FASTER speed / 120mb/s SD card is placed in the camera.

Nothing wrong with the SD card because it functions fine on my desktop and laptop computers.
I would post pics of the card(s), if you can easily do so. (Not if it's in the trail cam currently, obviously.)

It's possible that one is an SDXC, and one is an SDHC, and the SDHC works in the trail cam, but not the -XC, but the PC reads/writes either. (They are different standards / protocols for reading/writing the cards.)

Other than that, maybe one brand is just bad/buggy/junk, or maybe the (paper) specs on the "faster" card are wrong or exaggerated, and it's actually a much slower card.

Could maybe be an MLC/TLC/QLC issue too, with write endurance. Is one of the cards a "high endurance" card? Those are usually MLC, I believe, and intended for nearly continuously-written "dash cams", of which a trail cam would be a distant relative.
 

wpshooter

Golden Member
Mar 9, 2004
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Don't think there is anything defective about the cards because works fine with multiple slower 90mb/s cards and does NOT work with multiple 120mb/s cards. All cards are being formatted as FAT32 per Browning's recommendations and are then having the Browning's DELETED ALL function ran against them to eliminate any existing data/videos from them, again this is per Browning's recommendations.

Both cards are Sandisk and both are 32gb size and both are SDHC. The 90mb/s is an extreme with 3 in U and 10 in circle. The 120mb/s is an ImageMate with 1 in U and 10 in circle.

I also have some Sandisk Ultra 30mb/s circle 10 cards which work just fine in every Browning camera that I have.

Its as if for some reason these cameras do not like and will not function correctly with cards that are faster than 90mb/s. I know that I can just use the slower rated cards but me likes to know why this is required because would seem to me that if these speeds like 120mb/s are Maximums that they would be backwards compatible and work with the camera while seems to me that it would be the 30 & 90 mb/s that would be having the problems.

Again is the data flow / controller function in this case handled by the hardware of the trail camera or by the SD cards themselves ?

Thanks.
 

fralexandr

Platinum Member
Apr 26, 2007
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It's possible the slower cards actually work better at fat32 than the faster cards... most speed ratings are on ntfs.
Fat32 has a 4gb file size limit and canonically a 32gb capacity limit, so if those faster cards are actually larger than 32gb, they might be crippled by that.

You should run something like crystaldisk to check the speed when it's formatted to fat32 to get an idea of what it's actual speed is for your device.
 
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wpshooter

Golden Member
Mar 9, 2004
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If you are saying that I have transposed the reporting of the U ratings from the extreme model card and the imagemate model of the card, you are wrong, I am looking directly and the labels and I can assure you that I am neither misreading nor mis-reporting what I am seeing on each of these cards.

Imagemate card / 120mb/s has U1 and extreme card / 90mb/s has U3.

Thanks.
 

VirtualLarry

No Lifer
Aug 25, 2001
51,051
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If you are saying that I have transposed the reporting of the U ratings from the extreme model card and the imagemate model of the card, you are wrong, I am looking directly and the labels and I can assure you that I am neither misreading nor mis-reporting what I am seeing on each of these cards.
No, what I'm saying is, the U3 card is FASTER (for writing) than the U1 card, at least, by the rating on the card itself.

It's possible that the marketing material surrounding the card, is touting a 120MB/sec read rate for the ImageMate card, but that does NOT make it "faster" for YOUR application.
 

wpshooter

Golden Member
Mar 9, 2004
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So you are saying that the ImageMate "may" be the slower of the two cards even though it's rate is listed as 120 vs the other being 90 ?
But then how do you explain the fact that an SD card with a 30mb/s labeling will work fine in the camera ?
 

fralexandr

Platinum Member
Apr 26, 2007
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u1 has a minimum 10 MB/s write, u3 has a minimum 30 MB/s write
there doesn't appear to be any performance information on the imagemate regarding actual write speed.

your "30 MB/s" card might be capable of 30MB/s write
u1 and u3 are relatively recent specifications, so your 30MB/s card probably just says class 10 as that's the fastest class rating at the time it was produced.
Write performance is how fast data can be written to the card, i.e. your trail camera recording data. Read performance is how fast data can be read from the card, i.e. moving it to your computer or watching it straight from the card.

When using your u1 imagemate card, try reducing the video resolution, quality, or frame rate i.e. 1080p 30fps or 720p 30fps. It should write properly then.
 
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Insert_Nickname

Diamond Member
May 6, 2012
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So you are saying that the ImageMate "may" be the slower of the two cards even though it's rate is listed as 120 vs the other being 90 ?
But then how do you explain the fact that an SD card with a 30mb/s labeling will work fine in the camera ?
Have you tried formatting the card in the device itself? That may help. My old Sony compact camera will accept an SD card pre-formatted, but the performance is atrocious. Might be the same effect here.

Fat32 has a 4gb file size limit and canonically a 32gb capacity limit, so if those faster cards are actually larger than 32gb, they might be crippled by that.
FAT32 itself is good for 2TB volume sizes (16TB(!) if you use 64KB clusters), but that's not very practical. The 32GB limit is imposed by the SD card specification*, for larger cards you have to use ExFAT.

*and Microsoft. But that's a story in itself.

https://www.theregister.com/2021/01/04/windows_format_fat32/
 

wpshooter

Golden Member
Mar 9, 2004
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Insert_Nickname:

Yes, using the DELETE ALL function of the Browning trail camera does that (which is what Browning recommends) but make no difference, 120mb/s card still will not allow the camera to function correctly. But thanks for the suggestion.
 

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