In article <CnJn8D.Kox@crash.cts.com> shack@crash.cts.com (Randy
Shackelford) writes: 

>Well I just received an Apple ][ in the mail. As in original Apple ][, the one 
>before the ][+ even. The thing is it's missing a memory chip. Trying to track  
>down a 16K memory chip has been futile so far. Can anyone who used to have an  
>old ][ or ][+ help? As it came, it would turn on and beep but there was no     
>video. I tried removing an entire bank of chips, which got it where it would   
>flash a screen of question marks on the screen before going blank. Does anyone
>know if you have to change anything on the logic board when installing or      
>removing memory? 

Yes ! See below

>Does the memory start at the front row and go back or at the
>back row and go forward? Better yet, does anyone have any of the right kind of
>memory chips around or know of any? It will be really cool if I can get this
>fossil up and running.
>--
>Randy Shackelford                                "That's right, keep dancing
>shack@crash.cts.com                               on the minefield"
>                                                                  -Al Bundy


Hi Randy, How goes it across the ditch?
 

From page 70-71 of the Apple II Reference (1979) ....

The Apple's RAM memory is composed of 8 to 24 chips. These IC's are in 3
rows of sockets. Each row can take 4k (MK4096 or MCM6604) chips or 16 k
(4116) chips. 

The leftmost IC in a row represents the least significant bit (LSB) of each 
byte in the bank (blimey). The row of RAM ICs closest to the keyboard 
holds the first bank, and they progress in order (thankfully :-)

You configure the RAM by plugging memory control blocks into 3 IC sockets 
on the left side of the motherboard. The blocks are 14 leg bulky 
IC-looking things. There are no chips inside them, just wire-wrap 
jumpers. They must be modified to reflect your changed memory status. 

each one has pinouts thus:
               
                        keyboard end
                       ------\_/----- 
4k range $0000-$0FFF 1 |o          o| 14  = Frontmost row active
         $1000-$1FFF 2 |o          o| 13  = Middle Row active
         $2000-$2FFF 3 |o          o| 12  = Back Row active
         $3000-$3FFF 4 |o          o| 11  No Connection
         $4000-$4FFF 5 |o          o| 10  16k Range $0000-$3FFF 
         $5000-$5FFF 6 |o          o| 9             $4000-$7FFF
         $8000-$8FFF 7 |o          o| 8             $8000-$BFFF
                       --------------
                         other end

to specify a row as a particular bank of RAM you connect the ROW pin to a 
BANK pin ie you want the middle row of 16k chips to hold the range 
$4000-$7FFF... connect pin 9 to pin 13 and so on.

If you had 4K chips you would do a similar thing, connecting pin 9 to one 
of the pins in range 1 to 7.

Memory should always be configured as contiguous ie no blank bits and 
should always start from 0 (sorta makes sense :-)) but the manual points 
out that it doesn't have to be. You can use a memory map and pick out the 
memory bits you really like most.

WARNING: Revision 0 boards had a memory problem with 20 or 24k RAM, avoid 
this particular configuration if possible.

You should be able to get 4116 type 16k DRAMs from most electronic stores 
or buy another Apple II for about $A 30. :-( 

Hope this helps


Michael Hickey

u901841@student.canberra.edu.au