Re: Determining amount of RAM on a board?

[pausch@saaf.se (Paul Schlyter)]

In article <izmf7.31447$vW2.13893050@news1.sttln1.wa.home.com>,
Ernest <ernestls@home.com> wrote:
>Is there an easy way to find out how much RAM an Apple II has, or more
>specifically, an Apple II clone? I'm not familiar enough with the different
>chips to be able to easily tell by looking at the physical RAM on the board.
>If I see several rows of chips in the RAM area on the mainboard, how do I
>determine whether it's 48 or 64k?

The best way is probably to do it from software: access memory locations
at 16K, 32K, 48K, 64K etc and try to determine whether there's RAM there or
not: write a value, read it back, flip all bits, write it again, read it
back -- if you always read back what you wrote, there's RAM at that
address.

To reliably access the uppermost 16K of RAM (if any), the program should
be written in machine language executing at some low address guaranteed
to have RAM, since the uppermost 16K has both ROM and RAM, and if you
try the RAM test there with the ROM switched on, you won't find any
RAM of course.



-- 
----------------------------------------------------------------
Paul Schlyter,  Swedish Amateur Astronomer's Society (SAAF)
Grev Turegatan 40,  S-114 38 Stockholm,  SWEDEN
e-mail:  pausch at saaf dot se   or    paul.schlyter at ausys dot se
WWW:     http://hotel04.ausys.se/pausch    http://welcome.to/pausch