Re: Hardware emulation of 6509 using 6502?

From: Mike Naberezny <mike_at_naberezny.com>
Date: Thu, 15 Mar 2018 15:00:40 -0700
Message-ID: <d19ba9fb-5862-1177-9cd9-3ecfb632d6fe@naberezny.com>
On 3/15/18 1:55 PM, Michał Pleban wrote:
> I am not familiar with the 65816, so I have an obvious question - could
> KERNAL routines be called in the 65816 mode? If not, than the
> usefullness would be limited (no editor/KERNAL/BASIC calls, probably no
> interrupts as well).

I wrote a SoftBox terminal program that runs from the 24K RAM cartridge.  This 
program doesn't use the ROMs at all; it just uses the I/O devices directly. 
It has its own screen, keyboard, and IEEE routines (the IEEE routines are 
limited to what is needed for the SoftBox).  Porting this program to '816 
native would allow me to stop using the cartridge and have much more space for 
code and buffers.  It would also speed up the terminal, e.g. the '816 memory 
move instructions could be used to scroll regions of the screen.

For those times when the built-in routines are needed, the '816 can be 
switched to emulation mode to call the ROMs.  Although, with so much 
contiguous RAM available in '816 native mode, those routines could also be 
ported to '816 native and run from RAM.

I think the '816 adapter is worth pursing because it would be similar in size 
and cost to the existing adapter but would add powerful features for programs 
written to use them.

Regards,
Mike

-- 
Mike Naberezny (mike@naberezny.com) http://6502.org
Received on 2018-03-16 00:01:53

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