Re: Strange 8255 behavior

From: silverdr_at_wfmh.org.pl
Date: Wed, 13 Jun 2018 23:45:48 +0200
Message-Id: <C642B22B-14FF-4EFF-B5D2-4D0469506070@wfmh.org.pl>
> On 2018-06-13, at 23:27, Francesco Messineo <francesco.messineo@gmail.com> wrote:
> 
>>>>> probably the best thing would be re-creating a clone of the 6525 in a
>>>>> MAX7000 (5V series) CPLD. I can help (but I haven't a lot of spare
>>>>> time) if anyone likes doing that.
>>>> 
>>>> I am still waiting for someone to reimplement the 6526 replacement, which probably is in higher demand...
>>> 
>>> well, yes, I could try that indeed. I have the impression though that
>>> the 6526 isn't among the most scarce ICs. I was thinking just today to
>>> attempt to design a CPLD adapter to use a 6502 in place of the
>>> 7501/8501. Having a nice C16 without a working CPU annoys me and the
>>> 7501/8501 prices are outrageous.
>> 
>> By the time you finish the 7501, your TED will go belly up and you'll have next nice project on your desk :-)
> 
> well, I have repaired a few computers from the 264 family, I've never
> found a faulty TED, but I know they tend to die too.

In my practice they were even more die-prone than the CPUs. I'd say about 55 for the TED, 40 for the CPU. With the remaining 5 being ROM/RAM/other.

> The CPUs die more often. My C16's TED is still working fine (I can
> test it whenever I get a suitable cousin to be repaired).
> 
> It seems to me the 7501 isn't difficult to design around a 6502, if it
> only was more "documented".

Yea. The 6502 has been reimplemented multiple times so it would require "only" to know what needs to be done on top.

-- 
SD! - http://e4aws.silverdr.com/
Received on 2018-06-14 00:02:24

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