Re: Hardware emulation of 6509 using 6502?

From: didier derny <didier_at_aida.org>
Date: Thu, 22 Feb 2018 10:04:22 +0100
Message-ID: <9d00e424-552d-86e2-8d0c-2c1e6f40b8fe@aida.org>
if AEC is tied to VCC I wonder if it is possible to "plug" a 6502 and 
force P0..P3 to access only the main page and test the machine

(obvisouly a custom rom would be needed to test the functionalities)


it's useless to try to buy expensive stuff if the board is totally broken...




Le 21/02/2018 à 16:15, Mia Magnusson a écrit :
> 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 2018-02-22 10:00:14

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