Quote Originally Posted by superman View Post
..........., I am supposed not only to combine the RAM loader of 2588 with the remainder of 2996 but also to keep the HWID as 2588.
Exactly.

Read Post #6 again carefully as it's explained there. Some re-stating and finer details follow below.

I just wonder if I should use the GUPDATE.GCD originally from the 2588 and 2996 machines or the firmware files downloading from Garmin when generating the hybrid firmware.
The respective GCD files should be identical regardless of how you obtained them, provided they are of the same Version because ultimately all of them would have been sourced from a Garmin server anyway. That's whether they're downloaded directly from a Garmin website or loaded to the device via GarminExpress or WebUpdater. You can use the latest versions of the files from here:
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In addition, as seen in RGN tool, the .GCD file contains 4 .bin files, namely boot.bin, resources_7F05.bin, resources_9E05.bin and fw_all.bin. Does the remainder of 2996 refer to the files of resources_7F05.bin, resources_9E05.bin and fw_all.bin from 2996?
Yes, remainder is what you've inferred, the other sections of a firmware file i.e. other than the 'boot.bin' ramloader.

When setting the HWID by use of RGN tool, am I supposed to set the HWID not only in the firmware section but also in the Inventory and GarminDevices.xml by ticking the option of "Replace HWID text strings"?
Whatever you set using RGN_Tool will determine what's shown by the device subsequently in it's Inventory page and in GarminDevice.xml file if it successfully boots with hybrid firmware. Any manual changes you might make in the onboard XML won't be retained because the device re-writes it on every completed boot cycle. Remember in a hybrid conversion that you're retaining the HWID of the original device (2588 in this case).

Moreover, should the SW version be set as that of 2996?
Be sure to use the ORIGINAL device's HWID and also it's ramloader/boot.bin for a hybrid conversion, which in this case would be that of the US/EU device, i.e. 2588. For convenience and consistency i'd probably use the SW version (firmware version) of the APEC firmware advanced by ".01" (i.e. 3.51) although that's not so important, rather it's more to aid in personal recall and its identification as a hybrid fw, you could name it 7.00 if you want to avoid it being overwritten by GarminExpress later detecting it as a US/EU device due to its 2588 HWID being retained. Be aware that RGN_Tool being an older application doesn't deal too well with some later device firmwares so you need to be careful that it doesn't change region numbers etc. after saving, particularly in the 7F and 9E components. If you have problems then try with kunix's [Only registered and activated users can see links. ] instead.

This is how i'd try if i were attempting the hybrid conversion using RGN_Tool:
Spoiler: Click for Image
[Only registered and activated users can see links. ]

Then flash the RGN file in preboot. Note the specific file naming for the above would be 258801000351.rgn, reflecting the preservation of original US/EU HWID of 2588 and "01000" which tells Updater.exe to query and match the device's reported HWID to the file's HWID naming, for safety.

If you can successfully flash hybrid fw then a complete conversion using the full APAC fw will be possible. A failed hybrid flash doesn't necessarily mean it can't be fully converted however trying a full conversion first-off or if the hybrid attempt has failed might brick it. It could even hard-brick it irrecoverably. If it soft-bricks due to a failed hybrid conversion then it can be easily recovered because the original bootloader is still in region 5.