Re: [hatari-devel] DSP Bootstrap ROM

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Am Thu, 23 Sep 2021 13:24:22 +0200
schrieb Nicolas Pomarède <npomarede@xxxxxxxxxxxx>:

> Le 23/09/2021 à 13:18, Andreas Grabher a écrit :
> > The actual loop is some kind of hack, that partially simulates what
> > the bootstrap program does. While in that loop the DSP does not
> > run. That saves lots of host CPU cycles.
> > 
> > I don‘t know how the DSP is connected on the Falcon. On the NeXT it
> > is possible to select DSP mode by software via system control
> > register. Furthermore it would be possible to set the DSP to any
> > mode by writing to the OMR. But I did not yet see a program doing
> > that. 
> maybe someone needs to check falcon's doc first to see if such
> bootstrap mode is possible on real HW. If not, I'm not sure we need
> to backport this bootstrap code from Previous.

According to one of the DSP560001.pdf files from Motorola on my
hard disk, the bootstrap rom is built-in the DSP:

The bootstrap feature of the DSP56001 consists of four special
on-chip modules: the 512 words of PRAM, a 32-word bootstrap
ROM, the bootstrap control logic, and the bootstrap firmware


This 32-word on-chip ROM has been factory programmed to per-
form the actual bootstrap operation from the memory expansion
port (Port A) or from the Host Interface. You have no access to
the bootstrap ROM other than through the bootstrap process.
Control logic will disable the bootstrap ROM during normal oper-


Bootstrap ROM contains the bootstrap firmware program that
performs initial loading of the DSP56001 PRAM. The program is
written in DSP56000/DSP56001 assembly language. It contains
two separate methods of initializing the PRAM: loading from a
byte-wide memory starting at location P:$C000 or loading
through the Host Interface. [...]"

So I think we should include this in Hatari, too, but maybe leave it
disabled by default until we hit a program that really requires this.


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