Re: [hatari-devel] add support for TT ram -> problem with HD emulation and DTA

["Roger Burrows" <rfburrows@xxxxxxxxx>]

On 17 Dec 2014 at 17:13, Nicolas Pomarède wrote:

> Le 17/12/2014 17:06, Uwe Seimet a écrit :
> > Hi,
> >
> > It's probably not documented what exactly happens, but it's documented
> that
> > it doesn't work. (And it does not work, indeed.)
> >
>
> but what "doesn't work" really means ? Does the dma transfer stops when
> you read/write ? Does it complete but transfer garbage ? That's not
> precise enough to improve the emulation.
>
I understand, but don't forget "the best is the enemy of the good".  Even if
you don't know exactly how to report an error, or what error to report, you
should at least prevent the transfer from happening.  That would be much better
than allowing it.

> For example, I tested on my STF that if you read a sector with the FDC
> to ROM, then you won't get any error, nothing will be written to ROM of
> course, but you have no way to know the operation had no sense.
>
> Is this the same when using the HD on an STF, a TT or a Falcon, which
> have different HW / DMA ? Does the command fails or completes in all
> cases ? It's hard to guess without proper tests.
>
On a TT, to the best of my knowledge, no data is transferred if you try to DMA
to/from TT RAM.  There is no TT RAM on any other original Atari system, but I
believe that the same is true for the CT63.  I can easily write a program to
verify if you wish (I have the hardware).

Roger