Re: [hatari-devel] Small bug in Hatari Falcon emulation

[laurent.sallafranque@xxxxxxx]

Hi roger, 

> is the target location value just unmodified? 
> 
I'm just doing reads, so I'm not sure what you mean. 

He means 3 cases for a read :

The variable is set to 0

The variable is set to a random value

The variable is unchanged after the read

Regarde

Laurent

Le 23 nov. 2020 01:46, Roger Burrows <anodyne@xxxxxxxxxxxx> a écrit :

On 23 Nov 2020 at 1:08, Eero Tamminen wrote:
>
> On 11/23/20 12:47 AM, Roger Burrows wrote:
> > When the "STe Bus Emulation" bit (0x20) in the Falcon Bus Control Register
> at
> > $ff8007 is zero, "STe Bus Emulation" mode is set.  This affects bus error
> > handling.  Hatari already models this as far as the I/O memory area is
> > concerned (I haven't attempted to check how accurately yet).  But it also
> > affects bus errors when accessing RAM, which Hatari does NOT model.
> Basically,
> > on a real Falcon with "STe Bus Emulation" enabled, there are NO bus errors
> > generated for the whole $0 to $dfffff region, even in user state.  Even if
> RAM
> > isn't present at an address, no bus error occurs.
>
> Do reads to non-existing RAM areas produce some specific value like
> zero, or random values, or

A quasi-random sampling of values shows 0xff is returned.  That looks like a
floating bus (but what would I know, I'm a software guy).

> is the target location value just unmodified? 
> 
I'm just doing reads, so I'm not sure what you mean. 

Roger