Print Speed Issues in Firmware(possibly software)

I am a relative newbie to 3d printing(about 7 months of having a printer), I am trying to build a faster 3d printer. Before I started, I wanted to see how fast a printer could possibly go, so I went into slic3r and turned everything to 150 mm/s, the object I had (a pig figurine) took just about an hour to print. I then went back in and turned it up to 200 mm/s and so on and so forth until I hit about 300 mm/s and the time stayed the same. The estimated time in slic3r did not go down at all, I then purely out of curiosity turned it up to 1000 mm/s and the time continued to stay the same. I then changed the G-code flavor from RepRap/Marlin to Mach3(is used to for CNC machines) and it cut it down to 3 minutes. Sadly, mach3 is unusable in nearly all electronics. So far I have tried Cura, and got the same result. I have also made sure that all the the setting for my firmware is at an extremely high max above 2000 mm/s and acceleration above 10,000 mm/s. Any suggestions, or reasons that it caps out would be greatly appreciated. Also, I am curious why mach3 flavor can go much faster than RepRap/Marlin and all other flavors. I really would like to know before I build a printer that could possibly outdo the software. Thanks in advance!

Is the extruder speed capped??? Does the Mach3 have an extruder?????

I run only Mach3 on my printer with no issues at all. COMPLETELY usable! The extruder is run as a 4th axis.

The extruder is not capped at all. How did you get Mach 3 to work? I am currently using a Printrboard with Marlin, what firmware can I put on to make mach 3 work? I tried it, but the extruder would not run nor heat.

I'm running a TB6560 driver board, through an LPT printer port, manual control for hot-end and bed powered by the controller's spindle relay for end of print shut down. There is a way to run Mach3 to drive a USB controller but I have no idea what the configuration is or what USB boards it will work with. Check out the Mach3 forum at [www.machsupport.com]

Mach3 uses "A" instead of "E" for the extruder, If your gcode has E instead of A for the extruder, it will not run the extruder. You can do a replace E for A in a text editor. You may have to use different M codes for heat control.

I tried running it through a text editor already, and replacing the A with the E, I forgot to change out the hot end codes though. I will try that once I get to my home computer, thanks!