Re: A86: 24-bit addressing


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Re: A86: 24-bit addressing



On Fri, 5 Sep 1997, Matthew Johnson wrote:

> >462F _TRANS_AHL_TO_PAGED_AND_SET_PAGE
> >4633 _TRANS_AHL_TO_PAGED
> >4637 _INC_AHL
> >463B _DEC_AHL
> >463F _INC_BDE
> >4643 _DEC_BDE
> >
> >Those first two calls translate a 24-bit virtual address into a 16-bit
> >physical address.  4633 puts the RAM page in A.  462F goes a step further
> >and sets the page for you.
> >
> 
> 
> Sounds simple enough.  What is the syntax of 24-bit addressing? How do you
> convert between 24-bit (virtual?)
> addressing and 16-bit physical addressing (by hand) and vise-versa.


You don't convert by hand; you use 462F and 4633 (see above).  The 16-bit
portion gets returned in HL.  Sorry I forgot to mention that before.


>  Is the ROM 128K just like the amount of Ram in the 86?
> Am I making a mountain out of a mole hill?

No, the ROM is 256K (16 16-K pages).

> One more question.. where do you get these ROM calls from! Jee, you probably
> know the 86 better then Pat
> does :-)  Do you have some secret archive of rom calls you aren't telling us
> about?

No, I did some disassembly of the ROM last month.  I haven't done any in
the last 3 weeks because I've been devoting more time to my summer job.


> Oh and how do you respond so fast! I write a message, and you answer pretty
> darn fast!  Have you found a way
> to make genetic clones of yourself (with another one of his rom calls!)
> ........ that would explain alot :-)

No, but that would be great.  I could have an assembler ready next week.
:-)  I'm browsing the Jargon File tonight, so I've been online for a few
hours.  It's a really interesting hacker's dictionary that everyone should
check out:

	http://www.it.com.au/jargon/

Bye.

--------
Dan Eble (mailto:eble@cis.ohio-state.edu)
         (http://www.cis.ohio-state.edu/~eble)


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