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Old 05.11.2012, 12:50
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Thumbs up [GUIDE] How to solve most download CRC errors

I have been dealing with some download CRC errors and successfully solved the problem. I would like to share some tips and ask you about more ways to fix them.

1. Add Jdownloader files to exclusion list of Antivirus, firewall and HIPs software:
- Add the following files to the exclusion list:
JDownloader.exe, JDownloader.jar, JDownloaderBETA.exe, JDownloaderD3D.exe, JDownloaderPortable.exe, JDUpdate.exe ..
This step must be done in any of your antivirus, firewall or HIPs installed in your system. It may prevent possible lock ups while trying to write a lot of data in your hdd.

2. Limit your download speed by setting it to a bit less than your maximum download speed:
- Go here in order to check your maximum theorical download speed, and then set a limit in your jdownloader, with a bit less, about 10% less than your maximum download speed.
In example, if you maximum download speed is 5000kb/s, set it to 4400kb/s.
This setting could prevent packets to be lost because of network lock up, with a free space for the retransmision of packets and network data which will grant a secure download.

3. Check your hard disk state and defragment:
Its a good way of avoiding a lot of CRC errors. Check that your disk is in good state and fragmentation is very low. You can use the free wonderfull program defraggler to analyse your disk and defragment your files:
It may prevent to get corrupted downloads since most of the data will be downloaded in secuential sectors, and will avoid to move and write a lot of downloaded data in random locations. Make a backup of important things before beginning defragmentation.
*DO NOT defragment a SSD hard disk. Its not necessary and you can lost all your data.
*I would recommend not downloading data directly to a green 5400rpm hard disk. Those disks are known to be very slow and have bad stability (but just my thoughs).

Check that your HDD has good health and is working in the right Mode with tools like HD Tune Pro or AIDA64. In old computers you could find the old "PIO working mode" which is also known to be very slow and could be the cause of unknown hardware interrupts. Set working mode to Ultra DMA whenever its possible. (If you have hardware interrupts, Microsoft Windows Performance xperf is a good tool to detect the cause (driver) of unknown hardware interrupts seen with Process Explorer).

4. Make sure you have enough free disk space, about 20% of your total disk capacity.
This setting could be more or less depending of your total unit disk capacity, but make sure you have enough free GB all the time. Never leave the disk partition without free disk space.

5. Check your internet connection for network stability and errors:
Go to start, run, cmd.exe, right click on cmd.exe, RUN as Admin. Execute the following command line:
C:\>ping -t -l 1460 uploaded.net > network.txt
This will write a file called network.txt in c: drive, where you will be able to see if there are errors or packet losts.
A good report will have the following appearance, with 0 packet lost:
Haciendo ping a www.uploaded.net [] con 1460 bytes de datos:
Answer from bytes=1460 time=56ms TTL=49
Answer from bytes=1460 time=55ms TTL=49
Answer from bytes=1460 time=56ms TTL=49
Answer from bytes=1460 time=55ms TTL=49
Answer from bytes=1460 time=55ms TTL=49

If you have network errors you will get a lot of bad CRC downloads and you may also check for your router temperature, cables or even computer hardware. Reset any of them, change cables, check temps, press them...

6. Make sure you have the lastest stable version of JDownloader and the right Java version.

7. Delete temporary files and correct possible errors with ATFCleaner, CCleaner and Spybot SD.

8. Check for more usefull tips about CRC errors at this thread:

9. Check your memory modules for errors:
The best way to test for memory is with memtest 86+ (4.2.0). Download it, burn iso to a CD, and check all your modules for errors. If your modules doesnt have any errors, it will a good way of preveting a lot of CRC errors.
Degradation of memory modules after some years is a very common issue because of electricity, electromigration, temperature.. ( lowlevelhardware.blogspot.com.es/2012/04/electromigracion-en-microprocesadores.html )
Its recommended to replace the damaged modules with new ones of the same model and speed. If you cant find them because your mem modules are old, replace all your modules. Better to buy memory with low voltage and low timings

10. If you still get CRC errors, go to JDownloader and set MAX concurrent connections to 1 (Max. Con.), and set MAX downloads to 1 (Max. Dls.).
This setting could prevent possible hard disk IO lock ups and some background programs scanning too much downloaded data. Also downloading a file without concurrent download chunks, will be a safe mode to check for stability.

11. If you still get CRC errors, try excluding all java.exe. I would personally not recommend this setting since it may leave your system totally unprotected to remote java exploits, which are very common these days. Just do it only for testing stability:
c:\program files\java\jre6\bin\java.exe
c:\program files\java\jre6\bin\javaw.exe
c:\program files\java\jre7\bin\java.exe
c:\program files\java\jre7\bin\javaw.exe

There are probably a lot more steps to be done in order to avoid CRC errors, feel free to add, comment or correct anything you see in this guide. Thanks

Last edited by xtrm; 14.05.2013 at 21:51. Reason: Corrected some phrases for better understanding.
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