Quote:
Originally Posted by HarryT
Leaving to one side these doubtless interesting discussions of the definitions of different types of storage space, it's worth noting that PDF complexity is not just related to the size of images. A PDF page is rendered by executing drawing instructions stored in the PostScript language, and if a page contains complex diagrams, for example, these instructions can require more memory to execute than the Kindle has available. This can lead to the "out of memory" error that the OP saw.
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There are certainly other forms of complexity in PDF files that can consume memory, but generally, instructions to dynamically build a page are an extremely efficient form of "data aware" compression (the best kind). The real problem is the temporary storage buffers in RAM that these instructions use while building image layers that get displayed.
Full-page images of text pages (scanned books that were not OCR'd) use much poorer "generic" compression than dynamically generated images created from PostScript instructions, and are likely to consume more RAM just like they consumed more disk space on the USB drive.
Regarding using up available RAM storage space, OTHER apps that run "all the time" are stored in RAM while they are running, and they will also consume RAM storage space. You can see these with the "top" command from an SSH command prompt (which requires a hack). Kindles also slowly run out of memory and may need rebooting occasionally, to free up some RAM, due to how the single-process Java virtual machine allocates static memory for kindlet apps, which NEVER gets freed until you reboot.
There are reports in other threads that large PDF files that fail to load SUCCESSFULLY load after rebooting.