RE: JIffyDOS Coding

From: Marko Mäkelä (
Date: 2001-03-28 09:21:58

On Wed, 28 Mar 2001 wrote:

> Is there a "screen blanking" mode or something which keeps the TED running
> at constant speed?

Yes.  There are two settings: "screen blanking" and slow mode.  In fast
mode, the screen can be enabled or disabled.  When it is disabled, there
are 2*57-5 cycles per line available for the processor.  5 cycles are slow
ones, since those are memory refresh cycles.  When the screen is enabled,
the cycles not required for TED memory accesses are fast cycles.  This is
more intelligent than the 2MHz mode on the C128, since the screen won't be

I think that you could blank the screen and use either the fast mode and
take the memory refresh cycles into consideration, or the slow mode and
use the cycles sparingly.  The PAL C64 runs at 17734472/18 Hz, while the
PAL C16 clocks at 17734472/20 Hz (or /10 in fast mode).  For NTSC
machines, these figures are 14318181/14 and 14318181/16 (or was it /18?).


This message was sent through the cbm-hackers mailing list.
To unsubscribe: echo unsubscribe | mail

Archive generated by hypermail 2.1.1.