Hi Patrick Reread my post. That is just about all it does. It does have to initialize the port and that takes more than about half the code. The loop that loads the memory is quite short. The com port on the H89 is a 8250 and so needs a bunch of stuff setup. To load a value into the port I/O takes 3 to 4 bytes, regardless of how it is done. I suspect I can strip a little but I doubt I can take out more than about 10%. One thing I haven't tried is to use the Z80 I/O instructions and have a table of things to output in sequence. This might be shorter. Anyway, I've made it so that I can optimize it more after I get the rest of the functionality of the main code. There is a small amount of extra because I've not used a fixed load address or fixed size. I could shorten it a little and keep it flexable by only writing the load address. One would write the bytes backwards from there. At some point, the JMP instructions address would be over written by my new load code. The address of the high byte would be the same, just the low byte part of the address would change, directing the code to the newly loaded code. This would simplify the load loop since no count needs to be maintained ( a trick I learned form my Nicolet 1080's bootstrap ). I'll make another pass at the code and publish what I have. Others can then look at it for optimizations. Dwight