Re: what can run on a plain 48k Apple2 europlus

["Knut" <see-sig@online.no>]

"Michael J. Mahon" wrote:
> Linards Ticmanis wrote:
> > Knut Roll-Lund wrote:
> >
> >
> >>Grasping at straws: What if there is an adressing problem that data is
> >>overwritten because of an adress line failure. Would APTEST see that? Is
> >>there a RAM test that would test the address lines?
> >
> >
> > I don't think APTEST would see this at all. The RAM test in APTEST is
> > extremely simple minded: fill all of RAM with Value X, then test if it's
> > still there. Repeat for next X. This obviously won't find broken or
> > flaky address lines.
> >
> > You could try something simple like this (with no DOS loaded):
> >
> > 10 FOR I = 2500 TO 49000 STEP 2
> > 20 PRINT I;
> > 30 POKE I, 85:POKE I+1, 170
> > 40 NEXT I
> > 50 FOR I = 2500 to 49000 STEP 2
> > 60 PRINT I;
> > 70 POKE I, 170:POKE I+1, 85
> > 80 NEXT I
> >
> > Then see if and at what value of I you get screen corruption.
>
> Or you could take two passes, and store the high/low byte of
> the address at each address, then read back and verify.
>
> If any address line is open, stuck, or shorted to another, the
> values read back will not match.

Hi, thanks for the answers.

I have designed simple RAM tests through my work (embedded stuff). I would 
typically test address lines by using powers of two for each RAM area (in 
assembly using registers so the RAM is free) writing and reading back to see 
if they would affect each other.

I'm still learning about the Apple2 and especially I don't yet know where it 
is allowed to POKE. I could probably interpolate on your program and use the 
area 2500 to 49000 to test all the address lines, test separately within 
each bank of RAM.

BTW I did have a flaky RAM, at first, but identified it and fortunately I 
have some compatible spares. It sometimes got through the APTEST and 
sometimes not. I have been moving the RAM chips around so I'm pretty sure 
they work now (tested them all in the first bank). The faulty RAM was 
originally in the middle bank so DOS3.3 would boot fine even with it 
failing.

After changing that RAM the fault that is left is there all the time. 
Beautiful boot has never worked nor Wizardry or any other big games I have 
tried. Some smaller games work. There was something strange with the 
graphics on one lunar lander I tried but the game seemed to work (the 
hillsides were corrupted) I have no joystick or paddles for II+ yet so I 
couldn't test more there.

I have tried beautiful boot in several emulators in II+ mode but this is not 
a good test as emulators tend to have lots of extra "hardware". Should 
beautiful boot work on my plain II+ 48k machine with only a DiskII card? 
Beautiful boot is very typical on floppy images I find on the net and it 
seems to use HGR.

I'll try some basic when I get home from work.

--
Knut