Re: Building an Apple II from scratch

[et472@FreeNet.Carleton.CA (Michael Black)]

Dosius (steve@dosius.zzn.com) writes:
> mjmahon@aol.com (Michael J. Mahon) wrote in message news:<20030715024834.02823.00000128@mb-m02.aol.com>...
>> Great Hierophant observed:
>> 
>> >Yesterday, I took a look at the circuit diagrams and schematics of an
>> >Apple II found in the Apple II Reference Manual (the Red Book.)  I was
>> >struck with the number of components used, but also with their
>> >commonality.  In an original Apple II, there does not seem to be any
>> >custom chips or devices, unlike the later Apple IIes and IIcs.  Most
>> >of the Apple II/II+ seems composed of standard TTL logic chips.  The
>> >6502 CPU can be found.  The ROM, all 12-16KB of it, can easily fit on
>> >one EPROM.  48KB of DRAM can be done with two chips.   The connectors
>> >are probably standard.  Of course, one does not have to build a power
>> >supply  and can use an Apple II keyboard.  So, has anybody ever
>> >constructed an Apple II mainboard in the way I have described?
>> 
>> Steve Wozniak worked at HP Laboratories, and the Apple II was
>> constructed from parts available from lab stock (with the exception
>> of the 6502 itself).
>> 
>> HP at that time encouraged engineers to engage in projects on
>> their own time, and happily supplied the parts.  Very enlightened.
>> 
>> The result is that the Apple ][ and ][+ are easily constructed from
>> stock parts, and many were built like this in the early days, when
>> $1200 was a little steep for a device with $200 worth of parts.  ;-)
>> 
>> -michael
>> 
>> Check out amazing quality 8-bit Apple sound on my
>> Home page:  http://members.aol.com/MJMahon/
> 
> LOL, I once suggested to someone the possibility of building a 48K
> Apple ][+ with a PS/2 keyboard port and disk ][ emulation into a
> Commodore 1541 disk drive (also 6502-driven). :)
> 
> I wonder if it would be possible...
> 
I doubt it.  I'm pretty sure the "6502" in that drive is one of
the stunted ones, which don't have all the 16 address lines coming out
of it.  I can't remember if I read that somewhere, or saw it directly.

It also has limited memory.  And since one of the Apple II's claim to
faims is the nifty arrangement for refreshing RAM and displaying characters
on a screen with the same circuitry, terribly extensive work would have
to be done to add that to an existing 6502 board.

In other words, it would be easier to start from scratch than to try
to make an Apple II out of an existing 6502 board.

  Michael