More Apple II fun - 4116s...

[Tony Duell]

> 
> Converting the original IBM 5150 planar from 64K using 4116s to 256K 
> using 4164 was the subject of a number of kits--and magazine 
> articles.  It wasn't difficult.
>

A word of warning if you want to use all of the 4164 (as opposed to the 
mods we've been discussing so far that only use 1/4 of it) : Make sure 
you remove all the decoupling capacitors on what used to be the +5V line 
in the RAM array, and which becomes the A7 line. Typically there's 0.1uF 
per chip, and no normal driver is going to drive a 1uF capacitor to 
ground (i.e. 10 of the decouplers in parallel) without major timing problems.

Yes, the is the voice of experience. The Epson QX10 graphics board can be 
populated with either 4116s or 4164s. There are jumper links to select 
which ones are fitted,they basically do the pin-swaps we've been talking 
about. What none of the manuals point out is that if you fit 4164s, you 
_must_ remove the decoupling capacitors, or you get 'interesting' screen 
displays. One of my QX10s came to me non-working because the previous 
owner ad fitted 4164s, had done the link swaps correctly, but left the 
capacitors in. I spent some time sorting that one out...

-tony