blank when loading/saving from tape, not from disk

[moijk]

Why do the c64 blank the screen when loading/saving from tape, but not from disk?

 

[bdb]

It is a timing issue with the higher resolution screen (when compared to the Vic-20); the 1mhz 6510 CPU was over utilized keeping the screen active. This lead to blanking the screen on tape access which required very precise timing for accuracy (in fact the program is stored twice on tape with the two copies compared to each other). The c64 could not use the 1540 disk drive because it sent data too fast, so the 1541 was developed to send data slower. You could use a kernel that read the tape only once (?"Rabbit" is all I remember), but 6510 timing was crucial for a color 40 column screen. One can even speed up or slow down the CPU but it affects the screen colors. Remember, simplicity was often best back then. I mean does it make sense to give each disk drive their own 6502 CPU (same one that powered Apple II's and Atari's), their own RAM, & ROM? Or develop a C64 based disk drive controller (like the Amiga had)? The stuff from back then was based on economy not intellectual decisions; heck, look at the Amiga and the marketing/development, Gould was a pure schmuck. <-- my opinion. Poor Jack Tramel just passed away last week; he survived Auschwitz, only to be treated to losing his own company.