New Stuff For Old Stuff :: Blog

W ho doesn't enjoy a maths puzzle? I receive a Friday Quiz that always has a maths puzzle for Q18.  Sometimes it's something you can't calculate, like the smallest number of postage stamps to make up a particular value. The kind I like best are the ones you can solve with equations and test the answer.  Sometimes it's possible to use a spreadsheet or write a computer program.  Today's Q18 is the latter: 18. What is the lowest 3-digit number that increases in value by 75% when you reverse the order of the digits? My Minstrel the Forth (Jupiter Ace clone) was out and I've been using this a lot recently, writing a game as well as testing my keyboard interface. Spoiler alert: if you want to work it out for yourself, look away now. The answer is in the screenshots. There's definitely room for optimisation (the program is listed at the bottom of this post) but the inability to use nested loops made for a clunkier program and more work to get it working properly.  ...

 I n my last post I talked about the W65C02 and how it brought me closer to having all-new parts in my Vicky Twenty , and at the same time giving it some new instructions. That leaves the ROMs and the VIC. There's currently no replacement (as far as I'm aware) for the Vic1, but I have a new-old-stock one, so I think that's the best I can do for now. I'd already fitted a home-made Kernal ROM replacement . These are harder to obtain than the other two ROMs. That particular one seems to be less reliable. They're usually socketed, indicating that Commodore knew this. If you have a black-screen Vic, it's a prime suspect. That one wasn't very satisfactory. I didn't like the green adaptor board and thought it could be a bit more compact.   The other two ROMs were NOS (seem genuine) but all the same, I've always felt that they ought to be inside an original Vic-20, not a modern recreation. So I've had my own PCBs made and have made 3 matching ROMs for V...

L ast May my Vicky Twenty (Vic-20 clone) was progressing nicely. I claimed that all parts were new . At that point I had fitted a W65C02. A CMOS version of the 6502 which is still made today. The computer didn't work when I first switched it on, and it turns out that the W65C02 is not a drop-in replacement for the 6502 in a Vic-20*. A couple of connections are different, a pull-up resistor is required on one line, and most importantly, the logic levels on the Vic-20 board aren't high enough for the CMOS processor which requires a good strong high. The Byte Attic has worked on this problem and developed a circuit. He has been very open with this and it's now tried and tested. His board uses through-hole components, so it's large, needs sockets to raise it and then overhangs the Kernal ROM. I was proud of the looks of my Vicky Twenty and wished for something more discreet. I found that the transceiver was available in a surface-mount package and wondered whether the comp...