Why does the 8 bit C= run at 1MHz and the A8 run at 1.7+MHz
Posted: Sat Nov 19, 2011 8:26 pm
As put forward by Tezza as a post in its on right.
The one thing I find interesting as of yet its still a question of what known against what I have erad about the C64 is why does the Atari run at 1.7 odd and the C64 seems to run at 1 yet they both use an 8 bit CPU ?
Atari
CPU:
6502B (most 400/800 machines)
Atari SALLY 6502 (late 400/800 machines and all XL/XE machines)
CPU CLOCK RATE:
1.7897725 MHz (NTSC machines)
1.7734470 MHz (PAL/SECAM machines)
Commodore
The C64 uses an 8-bit MOS Technology 6510 microprocessor. This is a close derivative of the 6502 with an added 6-bit internal I/O port that in the C64 is used for two purposes: to bank-switch the machine's ROM in and out of the processor's address space, and to operate the datasette tape recorder.
which I have be told and have read some where on the internet only give a speed of about 1 MHz
But the VIC11
The VIC-II was manufactured with 5 micrometer NMOS technology[2] and was clocked at either 17.73447 MHz (PAL) or 14.31818 MHz (NTSC). Internally, the clock was divided down to generate the dot clock (about 8 MHz) and the two-phase system clocks (about 1 MHz; the exact pixel and system clock speeds are slightly different between NTSC and PAL machines). At such high clock rates, the chip generated a lot of heat, forcing MOS Technology to use a ceramic DIL package (called a "CERDIP"). The ceramic package was more expensive, but it dissipated heat more effectively than plastic.
Been looking around its seems the Commodore runs at more than one speed and can be 1MHz 2MHz or even 3MHz
see
http://archive.6502.org/datasheets/mos_6510_mpu.pdf
The one thing I find interesting as of yet its still a question of what known against what I have erad about the C64 is why does the Atari run at 1.7 odd and the C64 seems to run at 1 yet they both use an 8 bit CPU ?
Atari
CPU:
6502B (most 400/800 machines)
Atari SALLY 6502 (late 400/800 machines and all XL/XE machines)
CPU CLOCK RATE:
1.7897725 MHz (NTSC machines)
1.7734470 MHz (PAL/SECAM machines)
Commodore
The C64 uses an 8-bit MOS Technology 6510 microprocessor. This is a close derivative of the 6502 with an added 6-bit internal I/O port that in the C64 is used for two purposes: to bank-switch the machine's ROM in and out of the processor's address space, and to operate the datasette tape recorder.
which I have be told and have read some where on the internet only give a speed of about 1 MHz
But the VIC11
The VIC-II was manufactured with 5 micrometer NMOS technology[2] and was clocked at either 17.73447 MHz (PAL) or 14.31818 MHz (NTSC). Internally, the clock was divided down to generate the dot clock (about 8 MHz) and the two-phase system clocks (about 1 MHz; the exact pixel and system clock speeds are slightly different between NTSC and PAL machines). At such high clock rates, the chip generated a lot of heat, forcing MOS Technology to use a ceramic DIL package (called a "CERDIP"). The ceramic package was more expensive, but it dissipated heat more effectively than plastic.
'Carcenomy wrote:Yeap they do only run at 1MHz. Not sure why... you'd need to ask the designers. Could be to do with the timing of the memory modules they were using I guess?
Good grief, five posts and we're already back to computing as a topic!
Been looking around its seems the Commodore runs at more than one speed and can be 1MHz 2MHz or even 3MHz
see
http://archive.6502.org/datasheets/mos_6510_mpu.pdf