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Old 07-09-2013, 10:49 PM   #1
Ken Maltby
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Accessible Internal uSD card

Here are some pictures of a hatch I made that allows access to the internal uSD card of my AuraHD. It is made easy by the adhesive backed foam rubber cussion/gripping surface I applied, see post: http://www.mobileread.com/forums/sho...d.php?t=214575

Luck;
Ken
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Old 07-11-2013, 10:00 PM   #2
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I am interested to learn more on how to open up the AuraHD, mind taking abit more photos and some walk thru for case opening?

Thanks.
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Old 07-11-2013, 11:10 PM   #3
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Quote:
Originally Posted by 757470 View Post
I am interested to learn more on how to open up the AuraHD, mind taking abit more photos and some walk thru for case opening?

Thanks.
The case opening process is very simple. The case is made out of two basic parts, the case itself and a Bezel that snaps onto the case. The Bezel has little slots in it that slip over bumps on the inside of the case. (You can see the bumps in the first picture above that shows the inside of the case, with the electronics removed.)

The opening process is a matter of using something of about the thickness and rigidness of your thumbnail, to separate the slots and bumps. You just have to work it into the crack between the Bezel and the case and then work your way around the case slowly lifting the Bezel as you go to both move the slots away from the bumps and lift the two sided tape that is on the Bezel off the screen.

Luck;
Ken

Last edited by Ken Maltby; 07-13-2013 at 05:08 PM.
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Old 07-16-2013, 02:08 PM   #4
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Originally Posted by Ken Maltby View Post
Here are some pictures of a hatch I made that allows access to the internal uSD card of my AuraHD.]
I see a Class 10 SDHC 8GB cart in there. Do you know if those also work on the user SD slot?
I want to buy a HS-1 SDHC 32 GB. Might you know whether those will work with the Kobo Aura?
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Old 07-16-2013, 02:21 PM   #5
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There has been a lot of discussion in these forums over the benefits of different classes of SD cards. It's been shown that the class of the card is not the key factor in performance.
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Old 07-16-2013, 02:43 PM   #6
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So what is? The brand?
Hopefully not the size. With koreader finally being able to process scanned books in pdf my library will need the space.
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Old 07-16-2013, 03:19 PM   #7
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Try searching on "Small block writes".

For instance this post: (click on the blue symbol to see the original post with images).
Spoiler:

Quote:
Originally Posted by DNSB View Post
In the case of the Glo, that is what happened when I tried a factory reset.

When I was playing with the Glo, I found that selecting a uSD card with better small block writes made a very noticeable improvement in the speed of the device. Small block reads also seem to have a noticeable effect but the small block write speed is the one that varies horribly. I found that the SanDisk Class 4 cards gave me the best results.

Very often the Class 10 cards have done optimization for speed with large data blocks (writing 10MB on my digital camera). They seem to sacrifice small block speeds to obtain the better large block speeds.

I'm one of the people mentioning the lower class cards as being better in some circumstances. This originally came out of a Nook related discussion where some people found their Nook booted from an SD card performed well and others complaining this made their Nook run slower than molasses running uphill in Tuktoyaktuk in January.

I've attached 3 images from various Crystal DiskMark tests I ran on microSD cards (Lexar Class 10, Patriot Class 10 and a SanDisk Class 4 all 8GB) using the internal card reader on my laptop. In my digital and video cameras, the two Class 10 cards worked well. In my Glo, they made it noticeably slower. I suspect this is due to the small block writes where the Class 4 SanDisk was 65 to 171 times faster. The similarity of the sequential read speeds is, I suspect, a limitation of the Ricoh chip used for the card reader.

Regards,
David


Spoiler:

Quote:
Originally Posted by DNSB View Post
I'd suggest looking at a SanDisk class 4 uSD card instead. Do a search on small block writes for the reasons why. I posted some stuff in the memory upgrade with pictures thread in the Developer's Corner.

Regards,
David


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Quote:
Originally Posted by DNSB View Post
I played with the internal memory upgrade and have found that I needed to be selective with the SD card I used. I originally tried a Kingston class 10 16GB card but found that my Glo was noticeably slower than the original card.

So I had fun with testing various uSD cards and found the best one I had on hand was a Sandisk class 4 16GB card. Crystal DiskMark said it was much faster (1.81MB/s vs 0.019MB/s)* than the Kingston on small block random writes and 1.5x (3.1MB/s vs 2.03MB/s) faster on small block random reads. With that card, the Kobo is back to what seems to me to be the same speed as the original 2GB card.

* I ran the write test 4 times before I accepted the results. 95x was hard to believe.

Makes sense in a way since the original thread where I ran into the discussion of SD card speeds was installing CyanogenMod 7 on a Nook booting from the external SD card slot.

Regards,
David


Before you say it's just DNSB saying this, try searching via Google for people doing similar experiments on different devices.
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Old 07-16-2013, 05:37 PM   #8
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Quote:
Originally Posted by PeterT View Post
Try searching on "Small block writes".

For instance this post: (click on the blue symbol to see the original post with images).
Spoiler:




Spoiler:




Spoiler:




Before you say it's just DNSB saying this, try searching via Google for people doing similar experiments on different devices.
OH NO, that means there are more DNSBs out there!! Actually that it is "people doing similar experiments on different devices" gives it more credence, in my mind, than "Lab Results" or Bloger opinion. The results that I have seen posted suggest that much depends on the size of the files being accessed and if the use is through random access or sequential access.
My guess is that ebooks, even large ones, are accessed in small, a page or two at a time, increments. So I feel that DNSB has a valid point and Class 4 cards might be preferable over the Class 10 cards. (even if most class 10 cards are really class 6) I have not looked into the new classification system very much but I remember it as being touted as more reflective of performance in relation to multimedia files.

All in all, I doubt there is any great difference, but see no reason not the use the Class 4 cards for ereaders and the Class 10 for tablets. There is that most consumers would not be aware of this distinction and "(4)" is less than "(10)"; the class 4 cards should be cheaper. As you can see I would have no problem changing mine if I noticed any problem.

To answer your question, they all will work in the Aura it is a matter of a possible slight difference in performance.

Luck;
Ken

Last edited by Ken Maltby; 07-16-2013 at 05:44 PM.
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Old 07-16-2013, 06:56 PM   #9
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My guess is that ebooks, even large ones, are accessed in small, a page or two at a time, increments.
While your guess makes sense from the perspective of pages in a book, it is also worth remembering that ePubs are compressed. It is far more likely that ePubs are being accessed a file at a time (from the perspective of the container, not the file system) than in smaller chunks. I would imagine that the filesystem plays a role to, since they frequently cache data in order to avoid less efficient reads.
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Old 07-16-2013, 07:07 PM   #10
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While your guess makes sense from the perspective of pages in a book, it is also worth remembering that ePubs are compressed. It is far more likely that ePubs are being accessed a file at a time (from the perspective of the container, not the file system) than in smaller chunks. I would imagine that the filesystem plays a role to, since they frequently cache data in order to avoid less efficient reads.
Good point. But wouldn't the decompressed file be stored somewhere that the reading software accesses in the increments it needs?

Luck;
Ken
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Old 07-16-2013, 10:14 PM   #11
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To answer your question, they all will work in the Aura it is a matter of a possible slight difference in performance.
From what I found during my testing, it can be more than a small difference in performance. Quite a few manufacturers have sacrificed read/write performance for smaller files (<1MB) to improve performance handling large files. 2 Lexar 16GB U1 cards that work great in my D7100 (average RAW size is ~28MB, average JPG size is 11MB) are lousy in my Aura more than quadrupling the time required to process a batch of 500 epubs. Their 104MB/S U1 speed means very little when my average file size for an epub is less than 500KB while the chapter files in the zip wrapper for an epub average ~20KB after decompression. I might also note that the Aura mounts the cards directly, the D7100 needs a uSD/SD adapter.

Regards,
David

Last edited by DNSB; 07-16-2013 at 10:17 PM.
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Old 07-16-2013, 10:22 PM   #12
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Good point. But wouldn't the decompressed file be stored somewhere that the reading software accesses in the increments it needs?
The decompressed file(s) would likely be stored in RAM. As I mentioned, the decompressed size of the chapter files in my mythical average ebook is less than 20KB. Even decompressing the whole ebook file into RAM at once would take less than 1MB for most ebooks.

Regards,
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Old 07-16-2013, 10:26 PM   #13
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So what is? The brand?
Hopefully not the size. With koreader finally being able to process scanned books in pdf my library will need the space.
Brand wise, I found that SanDisk and Samsung both had consistently decent small block read/write performance. Several other brands had atrocious small block performance. Easiest thing to do on a Windows machine is to use CrystalDiskMark to do your own benchmarks. So far I have only done tests up to 16GB sized cards though I may be getting a pair of 32 or 64GB cards for my camera before heading out on vacation -- a 24 megapixel sensor is nice but you chew up storage space very rapidly.

Regards,
David
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Old 07-16-2013, 10:33 PM   #14
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I see a Class 10 SDHC 8GB cart in there. Do you know if those also work on the user SD slot?
I want to buy a HS-1 SDHC 32 GB. Might you know whether those will work with the Kobo Aura?
The Lexar UHS-1 cards I'm using in my camera also work in my Aura. Performance is not that great since their small block read/write performance is pretty poor.

Regards,
David
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Old 07-16-2013, 10:42 PM   #15
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@DNSB: Thanks for sharing all that. I should probably add some links to the SD discussions ot the tips thread.
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