Hello !!!
My name is Pedro, and this is my first post in the forum.
I've bougth a C64 as gift for my brother birthday.
He is a C64 fan, but he has been using vice since our previous C64 hadf crashed. Finally I decided to buy another. This Commodore was made in USA (NTSC).
When I first turn on, I noticed something strange ...
1514 bytes FREE !!!!. I was pretty sure that 38911 was the rigth number.
I tried to load programs using the dataset without success. They don't load or eventually crash.
After several retries, instead of the expected welcome (Commodore Basic V2 ....) appears OUT OF MEMORY IN 0.
I started to reading here, and the piggyback method and I'm ready to try this.
I've found a local IC vendor who has the 4164 chips in stock and also the 74ls257.
But, before this hard work, I made a silly test ...
I made several pokes and peek to different addresses and always recover the value previosuly written. Even after a short turn-off the values is there.
I tried several addresses:
2048
4096
15000
23000
35000
40000
With 0 and 255 values each one
Seeing the schematic and the 4264 datasheet, the memory is a 65536 bit memory and the 65536 byte memory bank was made with eigth of them in the way that every byte is composed from its bit outputs (D0-D7) .. D0 is always pin 2-14 of one 4164, D1 is the 2-14 of another and so on.
The question is:
Is one memory is blown, and every byte need one bit of that memory, how is it possible that writing 255 to one byte and then reading retunr the same value. Of course I tried with 0, and it read 0 also. If one chip were damaged, let's say that D7 chip is blown, after writing 255 you must read 127 .....
Where is the trick ????. I'm in my first steps inside the C64 ... so I need your help.
Many thanks for reading
Pedro.
My name is Pedro, and this is my first post in the forum.
I've bougth a C64 as gift for my brother birthday.
He is a C64 fan, but he has been using vice since our previous C64 hadf crashed. Finally I decided to buy another. This Commodore was made in USA (NTSC).
When I first turn on, I noticed something strange ...
1514 bytes FREE !!!!. I was pretty sure that 38911 was the rigth number.
I tried to load programs using the dataset without success. They don't load or eventually crash.
After several retries, instead of the expected welcome (Commodore Basic V2 ....) appears OUT OF MEMORY IN 0.
I started to reading here, and the piggyback method and I'm ready to try this.
I've found a local IC vendor who has the 4164 chips in stock and also the 74ls257.
But, before this hard work, I made a silly test ...
I made several pokes and peek to different addresses and always recover the value previosuly written. Even after a short turn-off the values is there.
I tried several addresses:
2048
4096
15000
23000
35000
40000
With 0 and 255 values each one
Seeing the schematic and the 4264 datasheet, the memory is a 65536 bit memory and the 65536 byte memory bank was made with eigth of them in the way that every byte is composed from its bit outputs (D0-D7) .. D0 is always pin 2-14 of one 4164, D1 is the 2-14 of another and so on.
The question is:
Is one memory is blown, and every byte need one bit of that memory, how is it possible that writing 255 to one byte and then reading retunr the same value. Of course I tried with 0, and it read 0 also. If one chip were damaged, let's say that D7 chip is blown, after writing 255 you must read 127 .....
Where is the trick ????. I'm in my first steps inside the C64 ... so I need your help.
Many thanks for reading
Pedro.