Elheat First, yes, your CPU is a bit slow (Passmark score of only 5734). Second, Prores is an intermediate codec used for exchange a video within the editing workflow. Thus it is less compressed than i.e. h264 files. You will notice scrubbing in ProRes files is faster than in h264 files. This results in a larger file size. Also ProRes encoding can't be GPU accelerated (with the current GPUs). So I think it is pretty normal.
Thank you Vouk for your explanation. but what i'm now coming across is a double-sized file. I.e, my original file from my camera is a 30MB MKV file, after exporting from DVR 17 using the proress codec, it turns out to be nearly 60MB. but if I use h.264, it could be 2 MB under 422, and 6 MB under 444. i understand that proress would be much larger than h.264 files, but i just can't understand why it could even be much larger than my original XAVC-I file. i've never used MAC and i've got little experience working with proress code(but i was always told it was good, so i wanted to try it). as a result, i'm not sure if this is a common result that you would get, of whcih i mean that whatever original file is, if you use proress, the exported file would always be larger than the original file.