Re: Hardware emulation of 6509 using 6502?

From: Mia Magnusson <mia_at_plea.se>
Date: Tue, 6 Mar 2018 20:51:37 +0100
Message-ID: <20180306205137.00006941@plea.se>
Den Mon, 5 Mar 2018 21:37:23 +0000 (UTC) skrev Steve Gray
<sjgray@rogers.com>:
> There was a 24K ram cart for the CBM-II series. It adds 24K into bank
> 15. I wonder if the P500 could use that ram for graphics/sprites?

Well, apart from the color ram with it's special access, it seems like
the 1k sram is the only thing VIC-II can see that resides in bank 15.

I really don't understand why this sram is there at all instead of just
map a part of the 64k dram in bank 0 as a 1k window in bank 15.

> IMHO, Commodore should have fully populated BANK 15 with 64K ram and
> made it possible to bank out the ROMs as the C64 does. This would
> have made the machines 100 times more useful and would have allowed
> large programs to run without all the overhead required to access
> kernal routines from other banks. Steve

Someone who were any good with software should had pulled some
emergency break before they actually sent the 6509 into production :)

What they could had done is fill all non-rom non-i/o parts of bank 15
with a mirror of bank 0.

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Received on 2018-03-06 21:00:02

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