my upgrade - following your path!
Great inspirational thread! Adding my experience:
Step-by-step: (excluding mistakes made on the way... 
)
1. Installed OpenELEC/XBMC on my AppleTV Gen1 (standard hardware setup) per instruction:
http://wiki.openelec.tv/index.php?title=Installing_OpenELEC_on_AppleTV
- Works fine! But 40 GB is too little space!
2. Purchased BCM970015 Broadcom Crystal HD Decoder from Amazon.de
- Seller: sc_computerecke via
www.amazon.de
- Price: 29,90 Euro
3. Purchased DELOCK Converter mSATA zu 2.5 IDE 44 Pin (62434)
- Seller: Amazon EU S.a.r.L.
- Price: 19,01 Euro
4. Purchased SAMSUNG 840 EVO SSD mSATA 256 GB
- Seller: online somewhere
- Price: dont remember
5. Tore down my ATV Gen1 according to instruction:
https://www.ifixit.com/Teardown/Apple+TV+1st+Generation+Teardown/439
- Removed the IDE hard drive
- Removed the wifi card
- Removed the fan
6. Used my Mac Mini (MacOS) to make a disk copy of the original AppleTV 40GB hard drive (OpenELEC installed on it!)
- Connected the hard drive to MacMini by using DELTACO USB 2.0 to SATA & IDE adapter kit
-- used the diskutil command to identify which drive identity it was given by system (disk1)
-- terminal command: dd if=/dev/rdisk1 of=./image.img (took ages to complete!)
-- Removed the original ATA drive from USB adapter
- Dualbooted into Linux on the MacMini
-- Attached the new SSD drive to the USB adapter
- used the PARTED command to identify which drive identity it was give by system (sdb)
- console command: dd if=./image.img of=/dev/sdb
--- disk cloning now compete, but the SSD looks like a 40 GB drive... so
- launched GPARTED to repartition the SSD
-- removed the LINUX-SWAP partition
-- recreated it at the end of the SSD
-- resized the STORAGE partition to maximum size
7. Installed new hardware into AppleTV
- Attached the SAMSUNG mSATA to the DELOCK converter
- Installed the CrystalHD card to the slot where the wifi card had been before
- Connected the DELOCK converter to the IDE cable
8. Connected the cables and booted the AppleTV
- After a minute or so, AppleTV shows error screen as if a boot disk not found
- Made a soft reset using Apple Remote control (hold arrow down, menu buttons for 10 seconds)
- AppleTV reset, and after about 40 seconds the OpenElec splash screen reappeared
- Go into system information -> available storage at about 250 GB
9. Remove all cables and close up the AppleTV casing
- let the SSD just lay as it falls in the case due to natural bending of IDE cable
- put some black electric tape over, just in case
- put the case lid back down taking care to not damage the white power plug which sits at the corner.
- screw back the four corner screws using the long ones at the right spot and the short ones at the right spot.
9. Upload gigabytes of data to the AppleTV
- Reconnect all cables (incl LAN cable) and reboot
- Use SSH / SAMBA from Linux to upload 10-20 GB of data
- Room temperature= 25 C, Peak ATV temperature= 67 C
10. DARN HAPPY !!!!
- Using XBMC skin Quartz (ATV lookalike)
- Very snappy and quick so far, moves around menus without any delays
- Sluggish only if SAMBA transfer ongoing at same time (30% CPU power for SAMBA transfer)
Non-central experiences:
-I started out with only a Torx 8, and it worked for the first disassembly and reassembly. But on second disassembly the Torx 10 screws were becoming difficult to get a grip on... Purchased the Torx10 and everything was ok. Torx9 can prolly be skipped.
-- Torx 8 for HD
-- Torx 9 for mPCI (?)
-- Torx10 for casing
- Take care not to remove all the rubber at bottom of ATV. I just removed portions of it to get to the screws and it still falls beautifully into place now that i am finished. No hairdryer required.
- I tried to install OpenELEC directly to the SSD using USB stick, but that kept on failing for some reason
- I tried to install Crystalbuntu directly to the SSD using USB stick, but that kept on failing for some reason
- I tried many other things, it all kept on failing and I believed the SSD was incompatible with the converter and/or ATV as the bloody fail screen kept on appearing when booting the ATV after anything i attempted to do.
- But then I realized that my Mac/Linux could read the mSATA perfectly through my USB-IDE adapter connected to the IDE-mSATA adapter so the hardware must actually be working... Is perhaps the Samsung too fast for the ATV ??
- Made the "dd" disk cloning activity and tried again...
- But failed too!
"I really give up. This sucks! - maybe buy a different, older SSD, anyway ATV is a piece of crap - consumes too much idle energy..." Sitting in the sofa 2 AM and staring at the bloody fail screen too lazy to do anything really-- maybe just one more attempt to reboot.. but too lazy to get up and pull the wires i did the soft reset using the remote... simsalabim, boot up perfectly! haha that was joy!
- In the end, it seems the
soft reset may have been a key to get the booting to function? Dont know why... Maybe the USB stick installations also would have worked if I had applied the soft reset... I recall some thread somewhere where something was discussed about soft resets to fix some similar problem... Anyway, now booting works both after power off as well as soft resets.
- I think the switching between MacOS/Linux is not needed. I was just a bit in despair thinking about hardware compatibility (JM20330?) and felt more comfortable using Linux to work on the repartitioning part.
Final note
So.. Thanks a lot for the inspiration you (Mondeo man etc) provided in this thread. I am really happy with my upgraded ATV1/OpenElec/XBMC! ... ATV3 goes to the bin!
