Yes...that's what i think sometimes, when "too many polygons" are being rendered on-screen, it slow down, but my PC is probably good enough to run it at full speed all the time, so the emulator might be the cause here.
My PC specs:
OS: Windows 7 Home Premium 64-bit | PSU: Corsair TX650W | Board: Asus P7P55D-E LX | CPU: Intel Core i5 750 @ 2.73Ghz | CPU Heatsink: Prolimatech Megahalems rev.B + Nexus 120mm fan | Memory: 4 x 2gb G.Skill DDR3-1600 | Video: eVGA Geforce GTX 560 Ti 1gb | HDD: Western Digital WD10EALS
OS: Windows 7 Home Premium 64-bit | PSU: Corsair TX650W | Board: Asus P7P55D-E LX | CPU: Intel Core i5 750 @ 2.73Ghz | CPU Heatsink: Prolimatech Megahalems rev.B + Nexus 120mm fan | Memory: 4 x 2gb G.Skill DDR3-1600 | Video: eVGA Geforce GTX 560 Ti 1gb | HDD: Western Digital WD10EALS