If you’re installing on a real 2015-era Mac, use a SSD – El Capitan on a spinning hard drive is still painful despite the optimizations. If you’re a collector or retro-computing enthusiast, this is the peak of “classic Mac OS X” before Siri and iOS features took over.
| Operation | Yosemite (10.10) | El Capitan (10.11) | Improvement | |-----------|------------------|--------------------|--------------| | App launch (cold) | 2.1 sec | 1.4 sec | | | PDF rendering | 1.8 sec | 1.2 sec | 33% faster | | Mail search | 4.5 sec | 0.9 sec | 5x faster | | Boot time (HDD) | 48 sec | 35 sec | 27% faster | download 10.11 el capitan
"This copy of the Install OS X El Capitan application cannot be verified" If you’re installing on a real 2015-era Mac,
Disconnect your Mac from the internet. Open Terminal from the installer utilities menu. Type date 020120161200 and press Enter. This changes your system clock back to February 1, 2016, allowing the certificate validation check to pass. "The download has failed" or Network Interruptions Open Terminal from the installer utilities menu
