Hello, I have a question how much it is dangerous to use swap on the mmc card. Some people mention that u will "fry" the card by constant access. But the Pretec card, I have got, came with life time warranty. So are these worries still valid?

Also I wonder if the whole card is destroyed or just the sectors with the swap.

2 things:

#1- firmware .51 no longer seems to work with any amount of swap (I've tried 16,32 and 128M) - i get out of memory as soon as I enable some and do something.

#2 - you want swap on a independant partition on the MMC, so that if you plug in the 770 into a desktop computer and it makes the MMC card go into USB Memory card mode the swap will be ripped out from the 770....

See the entry on my blog:
http://www.dillernet.com/apple/2005/12/27/making-swap/

it has some good info on this.

I don't use swap anymore with .51, it may not need it anyway. .48 did.

I can confirm that the week 51 download does support swapping. 32MB would crash the machine when it started swapping, 16 and 24MB work just fine. I have my swap on a separate partition.

No worries about wearing out the card. I created a "spare" swap partition just in case!

On the Syncing Apple's blog site, I noticed that Tommy Cheng's response to the posting of swap space gave me a somewhat killer idea.

Since I don't have SSH on my 770 (yet), I figured that I would create a simple text file to cut/paste into xterm. This is also useful if you don't have the bluetooth keyboard either.

So, here's the steps that I took to do this:

1) Obviously, your 770 has to have been modded to allow sudo gainroot. If you haven't done so, do it and continue to step 2.

2) Ensure you have xterm loaded.

3) Re-fdisk your mmc card to allow for two partitions. My second partition is only 24mb.

4) Start a web browser in your 770

5) Browse to: http://24.248.84.138/sgyee/770swap.txt

6) Select all, and copy the file contents

7) Open Xterm, sudo gainroot, and ensure you have a directory of init.d in /var/lib/install/etc . If not, make one.

8) Paste the file contents into xterm, not via the virtual keyboard applet, but from within xterm. Hit enter once.

9) Reboot. You now have it done, and you don't have to SSH or do any stupid typing to ensure that it works.

Enjoy!
-Steve

Flash cards of all current kinds include "wear levelling", which is supposed to spread writes around - in other words, every change to a file does not equate to a single erase cycle.

Clearly, the only way you could do this is by having writes happen to un-used blocks elsewhere on the card.

I haven't found anything that talks about the actual details of this. I don't know if there are "extra" blocks for this purpose, or if you'll find that your unused flash blocks are just grabbed for this purpose somehow.

However, there's a reasonable chance that you'll find that erase cycles are happening everywhere on your flash card, not just inside this one section.

I also speculate - but I'm not so sure - that having a less filled flash card will provide better wear levelling. It depends on the algorithm they use - also, it's not clear _how_ much a less-filled card would help.

In other words, depending on algorithm, you may find that a 24MB swap file on a 32MB flash card spreads the wear out as well as a 24MB file on a 512MB card - because the algorithms are optimized for the more likely scenario, of a nearly full card, with a few files that change every now and then, rather than a nearly empty card with one single constantly changing file.

The bottom line is: Nobody I have been able to find has been able to provide any serious information about how long your flash card will last as swap, and no matter what you do, using flash as swap carries the risk of prematurely ending the life of your _entire_ card.

Go forth and try it, and enjoy it, but don't use a flash card you can't afford to replace.

My swap experience http://www.nokia770tablet.com/viewtopic.php?t=30