Re: IIc ramp chips mapped from self-test

[dempson@swell.actrix.gen.nz (David Empson)]

In article <1993Dec24.080123.24549@presby.edu>
sebugg@presby.edu (Stephen Buggie) writes:

> Last week I asked the Apple group to help me interpret this error message
> on the self-test:
> 
>             RAM     0  0  1  0  0  0  0  0
> 
> I could not find the explanation in the IIc Tech Ref manual, which I have.

You didn't look hard enough.  It isn't documented in the main body of
the text (as far as I can see), but is documented in a comment block at
the start of the diagnostic routine in the ROM listing.  This is at
location $D4A9 in the auxiliary bank of the ROM, and is documented on
page 438 of the IIc Technical Reference Manual (first edition, 1985).

In your case, bit 5 of main memory was failing.  If it was auxiliary
memory, an * is printed first.

> I would recommend strongly that users of the oldest "original IIc" should
> take advantage of the free motherboard upgrade.  The upgraded board has the
> diagnostic self-test;  without the self-test, I would have had no clue
> as to which of the 16 chips was bad!

It isn't necessarily a motherboard upgrade - a ROM upgrade (and simple
motherboard modification) is all that is required to support the
UniDisk 3.5 and the improved self-test.  The motherboard upgrade fixes
the possible problem with the timing on the serial ports.
-- 
David Empson                                                               
dempson@swell.actrix.gen.nz                                                
Snail mail: P.O. Box 27-103, Wellington, New Zealand