Road Cycling - shimano 600

Well I heard different comments that the shimano 600 is a 7, 8 and 9 speed. I'm not too sure but would like to make sure before I go to a 9 speed setup and notice that it is not compactiable with 9. The main reason why I asked is that my bike right now is currently using all shimano 600 components but my shifters recently broke, so i'm thinking of just going to 9 speed using all the original 600 components. Thanks for all your help and all suggestion is accepted.

Shimano dropped the 600 designation when they went to ninespeed, so eightspeed was the last Ultegra600. I think sevenspeed was just 600 (Might be wrong on that, I have some 600 cranks on my fixed but it is a one speed.)

So, as pretty much all nine speed stuff is different from everything that predates it, you will not be able to just replace your broken shifter with a new nine.
You don't say what you have, but there are knockoff downtube shifters out there that are Shimano compatible. You can also get Sti shifters, Sora, in seven(Last time I looked) and eight speed.

Well I heard different comments that the shimano 600 is a 7, 8 and 9 speed. I'm not too sure but would like to make sure before I go to a 9 speed setup and notice that it is not compactiable with 9. The main reason why I asked is that my bike right now is currently using all shimano 600 components but my shifters recently broke, so i'm thinking of just going to 9 speed using all the original 600 components. Thanks for all your help and all suggestion is accepted.It would really be an enormous help to know how many speeds your 600 system is. It could even be pre-index 6 speed. Since you said your shifters (STI?)broke,I'm gonna assume its 8 speed.If that's the case, all you need for a 9 speed conversion is any 9 speed shimano shifters,cassette and chain. If it's not 8 speed, then there are more issues,biggest of which is rear wheel/hub needed to take a 9 speed cassette.

They dropped the "number" but actually the "number" changed from 600 to 6x00 (typically ZZ-6500 where ZZ indicates the part, crank, shifter, other...)

For example the Ultegra pedal that was designed to be used with the Ultegra 9-speed is the PD-6600.

The crank is the 6500
The shifter is the ST-6500

Note that Dura-Ace is 7x00 and 105 is 5x00

Oops the crank is the FC-6500

They dropped the "number" but actually the "number" changed from 600 to 6x00 (typically ZZ-6500 where ZZ indicates the part, crank, shifter, other...)

For example the Ultegra pedal that was designed to be used with the Ultegra 9-speed is the PD-6600.

The crank is the 6500
The shifter is the ST-6500

Note that Dura-Ace is 7x00 and 105 is 5x00 Even when it was '600', the PART NUMBERS were xx-64** for 8 speed and some other similar designation for 7 speed. Pre 9 speed the stuff was labeled 600 but was more often called ultegra.When it became 9 speed the label on the parts was changed to ultegra. The PART NUMBER designation also changed from 64** to 65** series.