Re: Hardware emulation of 6509 using 6502?

From: Mia Magnusson <mia_at_plea.se>
Date: Wed, 21 Feb 2018 16:15:37 +0100
Message-ID: <20180221161537.00002c41@plea.se>
Den Wed, 21 Feb 2018 10:52:24 +0100 skrev didier derny
<didier@aida.org>:
> for the 6509 I guess it's not so simple... the data has to be
> inserted at the right time and aec is missing on the 6502

Fortunitely, according to all the schematics I've looked at (P500, low
profile and high profile B's, at Zimmers mirror of the defunct funet.fi
site) the AEC is not used but tied to VCC using a resistor.

I don't know of any other 6509 based computers, so maybe the AEC were
never used.

The coprocessor slot of the B series uses separate muxes. 4-to-1 muxes
is used for the DRAM adress buss whith one input for the refresh
counter, two inputs for row/column in 6509 mode, and the fourth input
comes from the coprocessor connector. It's a bit strange that the
coprossesor only can access dram directly while everything in page 15
(I/O e.t.c.) is always connected to the 6509 and a hack using two
6526's connected to each CPU is used to communicate betweeen the 6509
and 8088. That could probably had been made nicer, but somehow it
works. It's interesting that the B refresh circuits is used also in
8088 mode even though the ras/cas muxing is done separately on the 8088
board in 8088 mode.

> for the 6525 I was thinking to use a GODIL, 
> http://www.oho-elektronik.de/index.php?c=1&s=index
> 
> I tried to replace a 6530 a few years ago, but the GODIL I was using
> was broken
> 
> I was testing on a kim but I had to give back the kim board before
> the working godil arrived
> 
> the main problem with the GODIL:  it is huge !!! and with all these
> pins a lot of risks for a short circuit
> 
> 
> there is also a product made by enterpoint, the craignel 
> https://www.enterpoint.co.uk/shop/home/48-craignell1.html
> 
> it's really expensive... and the options for he vcc/gnd pins are
> really limited

Back in the days there were a version of the Intel 8048 series that
acts like a peripherial. But I think it has too few pins and also it
uses Intel instead of 6800/6502 bus handshake.

Anyways it seems unnecessary to emulate all of an 6525 as the two first
ports seems similar to the common 6821 or maybe the rather common 6522.


> the cbm II is really new for me, I only saw them once at the Cebit
> 1982

About the same here, might have seen one at some fair back in 1983, but
have been reading about them now and then in recent years. But they are
so rare and seem so expensive that a replica might seem like a good
hardware project. :)

I know that I'm the kind of person who overthinks things and feature
creeps everything until it's not feasable, but I think some kind of
"universal-ish Commodore 8-bit board" would be nice.

Here in Sweden a guy who produce small add-ons for vintage computers
(for profit) is doing a thing that can emulate CBM keyboards. Something
similar would probably be necessary as PET, CBM-II/B, VIC20/C64 uses
different electrical keyboard layouts.

> I have a new world to discover :)

+1

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Received on 2018-02-21 16:00:03

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