The advertised speeds for your ssd are:
Sustained Sequential Read
Sustained Sequential Write
So, you are not too far off from what you should be getting.
Trim does work in IDE mode too, as long as you have win 7 or 8 on the ssd.
Really, then i guess its almost spot on. I was sure it was more because i had red somewhere that it was around 250-300 mb/s in the read section. TRIM is enabled, so i guess im in AHCI mode. I must say though, performance wise its really unimpressive, but its a couple of years old now so i guess its to be expected ;P