80-Bus News

First remove your IVC card. Then remove IC35 and lift up pin 14 so that it no longer engages in the socket and replace the chip. Connect pin 14 of IC35 to pin 4 of IC5 which is on the far edge of the board. Then turn the board over and connect pin 3 of IC5 to /M1, line 25 on the edge connecter (not too much solder here or the card may not go back in). Now replace the card and check that it works normally.

Conclusions

It took a while to get the whole thing running as I hadn’t realised that I only get one interrupt when the busy goes low. (I believe that I have read somewhere that this is due to the interrupt being generated by the high to low transition of busy).

I’ve been using my interrupt driven printer for over a month now without any real troubles. If you list a file to the printer, make sure that the power is turned on and that it is online or the system will hang up until it is. It should be possible to detect a permanent printer not ready and output a message but I have not yet attempted this.

After all the work I have achieved a 10% speed improvement in printing files (mainly due to there being no printer pause while reading the next sector off disk). This seems a modest improvement, but people with slower drives and/or printers should get more.