I used to use Turbo Assembler in the '90s for programming the C64. Recently I tried to find a newer version of it as I wanted a native assembler but the old version has some missing features. Guess what? Latest version has been released in 2006 under name Turbo Macro Pro. It is basically the same excellent assembler with integrated editor featuring autoindentation and immediate syntax checking, but lots of bugs have been fixed, support added for REU and IDE64 (I don't have those so haven't tested), and most importantly, macros, conditional compilation, local labels etc. that were missing in the original. Also as I have two unexpanded C64s, there is a version where editing can be done in one machine and code run in another, if they are connected via a custom cable. This could come handy if your data takes so much space so you can't keep the assembler in the memory all the time, and makes TMP a real crossassembler.

If you're interested, point your browser to http://turbo.style64.org/
BTW, I haven't coded this assembler or anything like that. I just happen to like it. At least the integrated editor is better than most PC editors for writing assembler programs (I usually use vim and have tried several others so I know what I'm talking about).

For the record, a "cross-assembler" is an assembler for microprocessor architecture X running on architecture Y, where X != Y. (E.g., a CP/M Z-80 assembler running under the Commodore 128's 8510A processor.)

A target assembler is one where it runs on host X and assembles for target Y, obviously where X != Y. The cable connecting the two is said to be an umbilical cable, and the monitor which runs on the target the monitor or umbilical monitor.

TSM is not a cross-assembler, it's a target-assembler.

Just trying to reduce confusion in nomenclature used in the industry.