Just got Comcast's Gig Eth WAN service, and though my OpenWRT router (Ubiquity Routerstation Pro has 4 gigabit ports, when directly connected to my Netgear CM1000 cable modem I get gigabit speeds (900mbps+), however connecting through my router I'm never seeing more than 80 or 90 mbps.
I checked swconfig and confirmed that both my WAN and LAN interfaces are negotiating at gigabit, and that my core switch is also negotiating at 1000 both to the router and to my workstation. While the router platform is not new, I also confirmed that my ram and CPU load are both low (20% and 11%, respectively), when under load (multiple speedtests).
I'm running Chaos Calmer 15.05.1, when the Lede fork remerges can I expect better performance for this platform or am I expecting too much out of 10 year old hardware? If the latter, what OpenWRT-compatible router on the market can support gigabit wirespeed throughput? Wireless is not a concern as I use external APs exclusively.
Depends on what your are expecting your router to do. With 18.08, as I understand it, many devices support "hardware offload" which lets hardware handle what previously required CPU cycles (in some hardware). If you're expecting complex firewall rules, bandwidth shaping, or the like, you may not have anywhere near enough CPU power. Managing gigabit rates is pushing out of the realm of SoC-based routers and into x86_64 boxes. Getting VPN at those rates moves you into high-end x86_64 CPUs with AES-NI or other crypto acceleration.
Just because you can get gigabit rates at home doesn't mean that it isn't "enterprise" rates that you're dealing with!
I'd look at the (long) thread so you can start forming your own opinions on options, should your current device not meet your needs