[fpc-devel] M68k: important milestone reached

[Sven Barth]

On 24.02.2014 18:06, Karoly Balogh (Charlie/SGR) wrote:
> Hi,
>
> On Mon, 24 Feb 2014, Sven Barth wrote:
>
>> Am 24.02.2014 17:29, schrieb Michael Schnell:
>>> On 02/24/2014 03:41 PM, Sven Barth wrote:
>>>>   are normally OS independant as they normally use corresponding CPU
>>>> instructions.
>>> Of course for simple stuff like inc/dec I can (better) use atomic 68 K
>>> instruction :-) .
>> Of course. But e.g. not every Coldfire architecture supports them. For this
>> reason I introduced the cpuflags CPUM86K_HAS_TAS and CPUM68K_HAS_CAS which are
>> set if the test-and-set and the compare-and-swap instructions are available
>> respectively (68000 only has the TAS, but not the CAS, 68020 and 68040 have
>> CAS and TAS while Coldfire ISA-A and ISA-A+ have neither and ISA-B and ISA-C
>> only have TAS). When I find the time I will implement the Interlocked*
>> functions accordingly :)
>
> Keep in mind that at least TAS is (basically) forbidden on Amiga, because
> it's incompatible with several HW implementations by Commodore and by how
> DMA accesses are generated by various bus extensions (Zorro II) or custom
> chips (eg. Agnus) in respect to the CPU and/or CPU expansion cards.
>
> The same applies to CAS/CAS2, I guess. Basically anything which tries to
> do an atomic read-write cycle is not guaranteed to work correctly on
> Amiga.
>
> More info:
> http://amigadev.elowar.com/read/ADCD_2.1/Hardware_Manual_guide/node012B.html
> http://www.devili.iki.fi/mirrors/haynie/systems/amiga2k/docs/tasa2k.pdf
> http://eab.abime.net/showthread.php?t=58493
>
> So if you decide to implement anything related to this, better make it
> OS specific too. :) Thank you.

Thank you for the warning. ^^ *marks the mail*

Regards,
Sven