Archive for June, 2010

High-Res Pictures of a MOS KIM-1

Monday, June 28th, 2010

The MOS KIM-1 is a quite rare collector’€™s item today. So if you hold one in your hands, you better take some high resolution pictures of the board. Here they are:

Note that this is the original revision of the board (pre-Rev A), and the 6502 CPU is from week 51 of the year 1975 – so it has the ROR bug!

Does anyone know what the three digit numbers 002 and 003 on the 6530 RIOTs mean? Are these the indexes of the ROM images? If so, what is ROM #001 and was there a #000? Also, the back has the number “0372″ on it – is this a serial number? Looking at the dates of the chips, this seems to be the oldest KIM-1 of all those I could find on the internet.

Posted in 6502, archeology | 6 Comments »

How much change is in a vending machine?

Wednesday, June 23rd, 2010

There is only one way to find out – all you need is a giant pile of money and a vending machine that sells soda for $1.25: If you put in a dollar note and press the “return change” button, you will get the dollar note back directly. If you put in two dollar notes (the maximum it takes) at a time, it will give you change for the two dollars.

Our machine had $29 of change. It started out with 25¢ coins, and after a while returned a combination of different coins (25¢ & 10¢, then 10¢ & 5¢), finally switching to all 5¢ coins at the end.

In total, it had

  • 25¢ x 57 = $14.25
  • 10¢ x 114 = $11.40
  • 5¢ x 67= $3.35

After this, the machine refused to take bills, so it was either full with bills or, more likely, out of change.

But actually, it might still contain up to 95¢ of change – today’s homework is to find out how to measure the remaining change in the machine!

Posted in hacks, puzzle | 15 Comments »