Who knew you could view .exr files in Blender?
I've just found out that in the UV/Image Editor in Blender you can open .exr files. So you can open a file the Queue Manager is creating and view the progress (Alt-R reloads it so you can see progress!) Woot!
Hmm... So, basically anything that can open a .exr file should be able to read it, even if it's being used as a live cache.
And, this is interesting: http://extension.nirsoft.net/exr
Apparently, IRFanView can open .exr files. That's a freebie program and probably has a much lower memory footprint than Blender. GIMP and Photoshop can also open that format. I'd imagine a great many image viewers/manipulators, either more recently developed or with plugin capabilities, can open that format.
IOW - You might have success with some different programs that won't take up as much of a memory footprint as Blender if you want to keep tabs on a render's progress.
You're probably right about memory, but as I've almost always got blender open anyway...
I do use GIMP so I'll see if I can read the files in that, tried before and couldn't but that was a long time ago (actually whilst waiting for my 5 minutes between posts (which doesn't appear to trouble the bots :) ) I tried, again it failed so probably need a plugin.
Interesting. It may be that the .exr generated by Cycles has a slightly different standard than GIMP's reader and/or some other programs that are reported to read the standard .exr format.