Hello,
I’m new to all this, before days buy a RB 150, in first tests it handles about 45 Mb/s but I have some issues in configuration.
Read some docs and see that upgrade is recomended.
Upgraded to Router OS 2.9.51 and now my RB 150 cannot handle more than 24 Mb/s
Not remember old OS version.
Tryed to disable all config without one dsnat (masq) nothing changes.
Tryed to use OS v. 3.10 - bad result bandwith drop to 16 Mb/s
Downgraded back to 2.9.51 and get stuck.
No older versions available.
Cannot find any clue how to get more bandwith on it.
My local reseler doesn’t sell RB 450 at all so I have to use this one (for home network).
You need more speed on your bridged ports? If true then this has already been discussed
http://forum.mikrotik.com/t/ros-3-ethernet-master-port-what-is-it/16153/1
It’s not just bridged, I use it to conect my home network to 2 ISP with failover.
I need to know how to get those initial 45 Mb/s that I got at the begining.
Nobody have an idea? 
Retry your tests with ROS 3.7 - I used that version and the cfer rate was about what you saw with 2.9 not sure why it dropped so much. Upgrade firmware on rb too when you goto ROS v3. There was one problem with firmware on rb150 you do not want to load that one - do a quick search to ensure you know which one it was FIRST.
Or - just jump to ROS 3.10 it should be fine too. maybe original test was flawed somehow?
Scott
As I wrote above:
Tryed to use OS v. 3.10 - bad result bandwith drop to 16 Mb/s
Downgraded back to 2.9.51 and get stuck.
Just to add - updated FW to 2.12 whit 3.10 it was inside ROS
morfius -
Well you should be able to get 40mbps with the RB150 on a wired network… Post your config as it sounds like something is wrong with your config.
You are able to get 45mbps to your ISP - where do you live 
If you are talking about ‘internal’ network speed you should get wire speed - so again - your config would be helpful in pointing you in the right direction.
R/