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Author Topic: Sheevaplug - 32 or 64 bit?  (Read 3341 times)
debio
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« on: July 08, 2009, 10:56:20 AM »

I'm wondering whether the Sheevaplug is 32 or 64 bit. I haven't received mine yet, or I probably wouldn't need to ask this. I know it follows the ARM architecture, but I'm pretty sure this distinction still exists there.
If a programmer wants check this, in C, you would just print sizeof(void*).

Edit:
Actually, could someone just post the output of `uname -a` ? That should give enough information about the system that we can figure it out.
« Last Edit: July 08, 2009, 01:31:44 PM by debio » Logged

tinker
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« Reply #1 on: July 08, 2009, 08:56:18 PM »

The documentation for the kirkwood processor is easily accessible.

Hardware:
http://www.marvell.com/files/products/embedded_processors/kirkwood/HW_88F6281_OpenSource.pdf

Functional:
http://www.marvell.com/files/products/embedded_processors/kirkwood/FS_88F6180_9x_6281_OpenSource.pdf

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areguly
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« Reply #2 on: July 19, 2009, 11:24:24 AM »

I know that's not what you asked but, given the embedded nature (lower hardware specs) it is actually worse to run on 64bit, as you gain nothing and the pointers cost more to store the same info... so even if the Sheeva supports it, you would have to hack it to add more than 4gigs of memory to make it worthwhile...
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debio
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« Reply #3 on: July 19, 2009, 11:44:22 AM »

This is true. I asked out of curiosity after I found out about the 2038 problem. I highly doubt my Sheevaplug will still be operational by then, but if it is, I'll have problems.
I'm not really worried about it.  Roll Eyes
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Blexley
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« Reply #4 on: July 19, 2009, 07:37:34 PM »

This is true. I asked out of curiosity after I found out about the 2038 problem. I highly doubt my Sheevaplug will still be operational by then, but if it is, I'll have problems.
I'm not really worried about it.  Roll Eyes


2038 problem Problem ?

Could you explain more

Thanks
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debio
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« Reply #5 on: July 19, 2009, 08:30:51 PM »

Well, it's basically the Y2K bug all over again, only this time it only affects Unix and Linux.
Unix and Linux measure time in seconds since January 1, 1970, and on some day in 2038, 32 bit versions of Unix and Linux are going to overflow their clocks and wind up showing that the time is somewhere way in the past. It's a good ways off, though, and I doubt many 32 bit systems will still be in operation.
For more, you can check out the Wikipedia article at http://en.wikipedia.org/wiki/Year_2038_problem
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Blexley
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« Reply #6 on: July 19, 2009, 09:45:17 PM »

Thanks for explaining Smiley

For a moment there i was concerned that 2038 was a some sort of eratta problem with the core of the Sheeva CPU   Grin

.

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tinker
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« Reply #7 on: July 19, 2009, 10:15:25 PM »

You are making the assumption that the date is being stored as one 32 bit number.  Easy enough to store it as two 32 bit values. Just a matter of the correct algorithm for storage and retrieval.
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debio
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« Reply #8 on: July 19, 2009, 10:21:43 PM »

Unfortunately, my assumption is also correct. The Unix time is stored as a signed 32 bit integer in Unix, Linux, and other operating systems, and it has been stored that way for a very long time. So many applications depend on this that it can't be easily changed. Even if the kernel code was modified to use a 64 bit signed integer instead, or even two 32 bit fields as you suggest, the bug would still exist and it would still have consequences because applications couldn't be adapted to the new format.
Furthermore, embedded systems like the Sheevaplug that are used in many environments where they are configured and left to run for years with no maintenance frequently cannot be updated, and thus will suffer from a problem like this.
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tinker
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« Reply #9 on: July 19, 2009, 10:33:29 PM »

Having worked on y2k issues I heard the exact same thing from nay sayers.  There is plenty of time for this to be fixed before 2038 and the changes have gone into some systems already. Embedded systems for which dates matter will be updated before then.

Many systems do not use dates at all and are irrelevant in this case.
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debio
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« Reply #10 on: July 19, 2009, 10:46:30 PM »

I'm not sure what your point is. I've already stated that I doubt many 32 bit systems will still be in operation, and I used the embedded device example just to show that changing the currently used date format isn't possible in many scenarios. I never said we were all doomed; this is just a problem on the horizon. It will probably cause some problems in the next 20 years, but due to the 64 bit move, I doubt there will be any immensely serious consequences.
In case it wasn't clear before, 64 bit Posix operating systems do store the time in a 64 bit signed integer, which will overflow in a few million years. Applications compiled for these systems also store the date in 64 bits. Ironically enough, the open source world is pretty much perfectly safe.
« Last Edit: July 19, 2009, 10:48:07 PM by debio » Logged

tinker
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« Reply #11 on: July 19, 2009, 11:25:56 PM »

You do not need to move to 64 bit architecture to fix this.
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Rabeeh Khoury
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« Reply #12 on: July 20, 2009, 12:03:11 AM »

Yup - 2038 problem is here

Following is on the plug -
debian:~/db# date 0119031438
Tue Jan 19 03:14:00 UTC 2038
debian:~/db# date
Tue Jan 19 03:14:02 UTC 2038
debian:~/db# date
Fri Dec 13 20:45:52 UTC 1901

I think Linux community has around 19 years from now to fix this issue  Wink
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bobnielsen
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« Reply #13 on: July 20, 2009, 12:03:04 PM »

If I'm still around by then (one week after my 99th birthday), I guess I'll have to worry about it but I expect I'll have bigger issues   Grin
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