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Re: [f-cpu] Supported Instructions



Yes, I see what you mean! But actually you could already
start with f-cpu prototyping when you just have basic
instructions running. Some while ago I read in an article
that it would be enough to start with a bit test, a bit
modify and a jump instruction. You may be able to emulate
everything else with them. So why not (at least) think
about this way?

JG


On Sun, 7 Apr 2002, Christophe wrote:

>In my mind, invalid instruction always triggers a trap.
>
>If you want to emulate some instructions (whatever you want) and be able to
>access the F-CPU registers to read, you can have a speed up using the
>possibility that an invalid instruction traps updates three SRs which will
>contain the contents of three registers fields of an opcode (valid or not for
>this opcode). So when we execute the handler it can quickly have the contents
>it needs to compute without need to get them from CMB. Of course we still need
>to update those registers in CMB if necessary. If you want to emulate an
>instruction without registers fields, well, just let the emulation ignores
>those three register operands.
>
>But okay, it is just a suggestion for the problem of a CMB not totally saved
>(when our three registers are not saved yet in the CMB), but, I must admit, I'm
>not totally convinced with this suggestion :).
>
>----- Original Message -----
>From: Juergen Goeritz <goeritz@oekomm.de>
>To: <f-cpu@seul.org>
>Sent: Sunday, April 07, 2002 7:02 PM
>Subject: Re: [f-cpu] Supported Instructions
>
>My idea is to implement nothing at all for unimplemented
>opcodes to be free for future changes. And unimplemented
>opcodes should always generate an exception.
>
>
>
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