> -----Original Message-----
> From: Laurens Holst [SMTP:[EMAIL PROTECTED]]
> Sent: Wednesday, September 16, 1998 8:52 PM
> To: [EMAIL PROTECTED]
> Subject: Re: Memory Mapper mirror effect?
>
> > Anyone knows if there are memory mappers with mirror effect (i.e.,
> > for example, a 128k mapper (8 pages), if I select page 16, I'll get page
> > 8). I don't know any, but maybe there is...
>
> All mappers do this 'mirroring'...
> If they didn't then it would not be possible to detect the mappersize...
> (only legal mappersize-detection is done by using the mirror-effect).
>
It would be possible if selecting a page that doesn't exist results
in selecting memory that is not present.
Then data written to an address in that page can not be read back.
In fact. it would be simpler then:
10 i=0
20 out &hfe,i:d=peek(&h8000):poke&h8000,d xor 255
30 if peek(&h8000)<>d xor 255 then 100
40 poke&h8000,d
50 if peek(&h8000)<>d then 100
60 i=i+1:if i=256 then 100
70 goto 20
100 print i;:print " pages of mapper RAM"
Well, something like this...
Greetz,
Patrick
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