The inputs of the 74LS153 chip were mixed, which caused the address block decoding to fail. By now, I know of two Commodore 64 (mine and Pekka Pessi`s) where this expansion has been built, and of four Commodore 128s (of which two expanded by me, and the other two by Wolfgang Scherr and Matthias Kirchner from Germany). The expansion never became a success, although
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the banked concept is technically better than e. g. the Commodore REU. Meanwhile, there is one more program that supports the expansion: my transfer system prlink. Commodore 64 becomes remarkably more efficient by adding memory to it. Then the worst slow-down, incredibly slow disk drive, can be worked around by using a part of the memory as a RAM disk. In 1986, when the original article was written, there were no commercial memory extensions for sale in Finland. (Commodore`s RAM Expansion Units came to our market in the year 1987. ) Of course there were some in the USA, but they were quite useless, as they had only 64 ½kB of memory, and the price was high as well. When built by oneself, the following memory expansion should have costed 300-400 Finnish marks. One American dollar (USD) is equivalent to five or six Finnish marks (FIM). I constructed my expansion in 1993 March, and it costed 111 FIM. It could easily have been about 20 FIM cheaper. Many goals were set to the expansion. As many programs as possible should work also with it installed. This means that there could not be any radical changes to the memory map. The address space of an expanded machine really remains same for a usual programmer. After reset, the computer doesn`t differ from an unexpanded one practically at all. Even taking a look at the machine from outside doesn`t reveal the expansion, as Pekka needed the expansion port for his IEEE-488 interface...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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