Re: Hardware emulation of 6509 using 6502?

From: groepaz_at_gmx.net
Date: Thu, 09 Nov 2017 18:58:51 +0100
Message-ID: <1576848.ZPG0gtpG4N@rakete>
Am Donnerstag, 9. November 2017, 18:37:20 CET schrieben Sie:
> On Wed, Nov 08, 2017 at 11:01:29PM +0000, smf wrote:
> >On 08/11/2017 18:06, David Holz wrote:
> >>On writing to 00/01, the 6510 enables a Write on the bus but doesn't
> >>assert the data pins. In the C64, the net effect is that the lingering
> >>prior data value from the VIC-II's bus phase will get written to those
> >>RAM locations.
> >
> >Does it have the same reliability issues to running code in de00/df00
> >from vic fetches, which vary by motherboard capacitance and
> >temperature.
> 
> I expect so. BTW, this question was asked here only a few weeks ago, and
> if I remember correctly, in reply to my reply, Groepaz posted a link to
> his test program that writes and reads the memory locations 0 and 1.

its actually quite reliable (just like the unconnected I/O, btw) - reliable 
enough that some copy protection used it (unfortunately i forgot what game it 
was... but it was a very good obfuscation)

-- 

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