4 ms·
You can’t just "drop in" a faster 6502 (or 6510) into something like a C64. For one, all the serial i/o routines are software bit-banged so parts of the "ROM Ke
by basementcat 5y ago
You can’t just "drop in" a faster 6502 (or 6510) into something like a C64. For one, all the serial i/o routines are software bit-banged so parts of the "ROM Kernal" need to be modified. More importantly, the VIC-II chip is the DRAM memory controller and it is tightly coupled with NTSC or PAL signal timings.
Most accelerator boards for the C64 need quite a bit of glue logic to overcome these difficulties.
- tyingq 5y agoIt has some of that accounted for, like: "Upon power-on, the 65F02 grabs the complete RAM and ROM content from the host and copies it into the on-chip RAM, except for the I/O area. Then the CPU gets going, using the internal memory at 100 MHz for all bus accesses except for any I/O addresses" There's also some soft cores for a Z80 that can work at the stock clock speed, but do more work per cycle, which is interesting. Edit: Some, not all, things are covered.
- basementcat 5y agoThe reason why many 8 bit home computers put the memory controller in the graphics chip was to give the graphics subsystem "first dibs" over bitmap data in RAM. If the microprocessor has its own copy of RAM then the graphics subsystem may never update the display unless the cpu "writes through" all memory write operations (resulting in a significant performance slowdown).