Re: Update on Apple II rev 0 replica kits

[Mike Willegal <mike@willegal.net>]

Hi,

I think the old Apple II reference manual has a description of most of 
the functional differences between Rev 0 and later revs.  There is a 
scanned copy online, somewhere. Also my website has pages that detail 
most of the differences.

http://www.willegal.net/appleii/appleii-recreation.htm
http://www.willegal.net/appleii/appleii-pcb.htm

Power up without reset results in a random text filled screen and no 
prompt.  Actual display depends on what state memory comes up in.  My 
experience is that the screen is mostly filled with the same inverse 
character, with a few oddballs spotted around.  I am unsure of what the 
processor is doing - it would take a logic analyzer to determine if it 
normally processes instructions, without a proper reset, or just hangs. 
 I suspect you could simulate the display simply by holding down reset 
when powering up a later rev board.


You are pretty much on the mark for very early systems coming with 4K 
memory.  Systems with more memory were available from Apple, but were 
VERY expensive.  Most folks purchased aftermarket memory, soon after 
purchase, as 4k was very restictive.  I tried to enter a program from 
David Ahl's Basic Computer Games book, and it wouldn't fit into my 4K 
system the very first night I brought the system home.   I ran my system 
with 36k for a long time, because even aftermarket memory was expensive.

Regards,
Mike Willegal

Bryan Parkoff wrote:
> Mike,
>
>
> > Correct - rev0 - only 4 colors in hi res mode, no built in reset (although 
> > disk II controllers have a reset circuit).  24K memory bug, etc.
>
>
>     Can you please describe what RESET look like?  For example, you turn on 
> the power supply.  The screen should be frozen showing 16 colored LO-RES 
> blocks.  MPU might operate without initializing all internal registers.  You 
> press RESET key manually every time after you turned on.  Then, monitor 
> prompt comes back to normal.  The LO-RES screen will be switched to TEXT 
> screen.  Is it the way how the procedure goes?
>
>     Can you please list all bugs from original Apple II rev 0's motherboard? 
> I am curious to know.
>
>     I suppose that Apple II rev 0 only has 4 KB RAM.  Integer BASIC can be 
> written to manipulate LO-RES / TEXT screen, but it is limited to 2 KB RAM. 
> Other 2 KB RAM is used for zero page, stack page, buffer page, and TEXT / 
> LO-RES page.
>     I guess that earliest games were released with LO-RES screen until 
> people could afford to buy extra 4 KB RAM or 16 KB RAM.  With 16 KB RAM, 
> they were able to write first page of HI-RES.
>
>
> > I don't supply power supplies, case and keyboards as they can be easily 
> > obtained from an inexpensive apple II plus.
>
>
>     I thought that original Apple II rev 0's keyboard and Apple II Plus' 
> keyboard are different design, but they operated the same.  Is Apple Plus' 
> keyboard compatible to Apple II rev 0?
>
> Bryan Parkoff