65c802

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Dbug
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65c802

Post by Dbug » Wed Mar 18, 2020 10:21 pm

A few weeks ago, I managed to find a rather uncommon variant of the 6502 family, the 65C802, which is an hybrid between the 65c02 and the 65c816, pin compatible with with the 65C02, with all the instructions and special features of the 65c816, but without the ability to access more than 64k of memory.

I did a quick check, and yes, that worked - with some weird side effects - but that worked:


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Re: 65c802

Post by Dbug » Sat Mar 28, 2020 10:12 am

Hmm, it looks like the machine is having problems starting up: 9 times out of 10 it just freezes on startup, but when it works it just runs fine (same behavior with normal 65c02, not just with the 65c802).

By looking at various messages from people who installed 65c02 on 6502 based machines (including Apple II and Oric/Pravetz), I've seen the following solutions:
A - Just plugg it, it works! (rarely)
B - Just bend the pin 1 so it's not connected
C - Add a 1ko resistor to the pin 1
D - Bend the pin 1, and also connect together pins 8 (VCC) and 36 (BE)
E - Bend the pin 1, and also connect together pins 2 (RDY) and 36 (BE)
F - Add the 1ko resistor to pin 1, and also connect together pins 2 (RDY) and 36 (BE)

I've tried A (did not work), B (Worked about one out of ten boots), D (worked like B).
I've not tried C, E or F.

Any suggestion?
Should I check things like the "63b modification on IC21" mentioned page 35 of the service manual?

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Re: 65c802

Post by Chema » Mon Mar 30, 2020 11:44 am

Dbug wrote:
Sat Mar 28, 2020 10:12 am
Hmm, it looks like the machine is having problems starting up: 9 times out of 10 it just freezes on startup, but when it works it just runs fine (same behavior with normal 65c02, not just with the 65c802).
Random comment :) A friend of mine was complaining about his Oric not booting most of the times and he opened it up and replace all the capacitors. Voilá: it now boots every time :D

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Re: 65c802

Post by Dbug » Mon Mar 30, 2020 5:03 pm

Guess it's worth trying :)
By all capacitors, do you mean ALL, or just the chemical ones?

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Re: 65c802

Post by Chema » Tue Mar 31, 2020 9:36 am

Dbug wrote:
Mon Mar 30, 2020 5:03 pm
Guess it's worth trying :)
By all capacitors, do you mean ALL, or just the chemical ones?
Let me check his message in the Telegram group...

Found it! He said he changed 3 capacitors: the one of the RESET circuit 1uf (he put one of 10 instead, and said the booting is much more stable), one of 100 uf and the last one of 22uf. And he also said that the buzzing sound from the speaker has disappeared :)

So probably just the chemical ones.

By the way, he is the one who just finished the Oric + Microdisc FPGA core for Sidi, Mistica and Mist, and the one which has just been ported to Mister too!

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Re: 65c802

Post by ibisum » Tue Mar 31, 2020 12:50 pm

>Oric + Microdisc FPGA core for Sidi, Mistica and Mist, and the one which has just been ported to Mister too!


!!! Interesting!

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