Weird Incompatibilities...

naI · April 09, 2009, 09:58 AM

Some game programs (most notably, "Elite"

) appear to be corrupted on my Commodore 128, but work just fine on my friend's C=64c. Using my friend's 1541-II drive doesn't rectify the issue, either. I do not use any fast loader cartridges, and disabling JiffyDOS produces the same results. Just what could be causing this?

SmallCleverDinosaur · April 09, 2009, 09:17 PM

In what way is the computer corrupted? What are the symptoms?

Does the C128 show 38911 bytes free when started in C64 mode?

Wasn't Elite one of those games that was "enchanced" when used in C64 mode of a C128? If so, maybe it uses the VDC memory and you have a VDC upgrade that might cause the problem.

naI · April 09, 2009, 11:13 PM

There is graphical corruption (garbage) on the screen during or after loading, depending on the program, that ultimately results in a crash. Elite displays several screens of garbage, when it should display an animated ship coming from a black screen. The results are the same when I use GO64 or start up with the C= key pressed down.

64 mode shows 38911 bytes free.

Quote from: SmallCleverDinosaur on April 09, 2009, 09:17 PM
Wasn't Elite one of those games that was "enchanced" when used in C64 mode of a C128? If so, maybe it uses the VDC memory and you have a VDC upgrade that might cause the problem.

As far as I know, it wasn't enhanced. I do know that there is an enhanced hack out there for the C=128, but I have the original. I just recently upgraded my VDC, and this problem existed before I did that. But the C=64 mode uses the VIC and I don't think it has access to the VDC.

Alex · April 10, 2009, 07:27 AM

Do you have anything else connected to you C128?

naI · April 10, 2009, 10:32 AM

Quote from: Alex on April 10, 2009, 07:27 AM
Do you have anything else connected to you C128?

A C2N datasette. But unplugging it doesn't help.

RobertB · April 13, 2009, 11:38 AM

FWIW, I have had few problems loading and running games into my C128DCR.

Truly,
Robert Bernardo
Fresno Commodore User Group
http://videocam.net.au/fcug
Notacon 6 / Blockparty 3 on April 16-19
http://www.notacon.org , http://www.demoparty.us

naI · May 04, 2009, 11:53 PM

I'm still wondering about this. Does anyone have any ideas as to what's causing the incompatibilities? It it even something that can't be helped?

SmallCleverDinosaur · May 05, 2009, 12:32 AM

Do you have an original version of Elite? Or is it a copy? If so, you can transfer it to a d64 and post it on the forum so we can test it in our computers.

And just to make sure, you do have a NTSC version of the C128? You didn't by it from ebay Europe or another place that could have sent you a PAL version?

Wes · May 05, 2009, 10:28 PM

Have you tried holding down CAPS LOCK when you boot?

See:

QuoteSome of the few C64 programs that fail on a C128 run correctly when the CAPS LOCK key is pressed down (or the ASCII/National key on international C128 models). This has to do with the larger built-in I/O port of the C128's CPU. Whereas the SHIFT LOCK key found on both C64 and C128 is simply a mechanical latch for the left SHIFT key, the CAPS LOCK key on the C128 can be read via the 8502's built-in I/O port. A few C64 programs are confused by this extra I/O bit; keeping the CAPS LOCK key in the down position will force the I/O line low, matching the C64's configuration and resolving the issue.

BilHerd · May 23, 2009, 05:55 AM

I'd have to go with cursed... do you have some chicken skulls laying around that we could use for a cleansing?

Seriously if you get garbage characters, especially if they just happen, then something is probably hosed at a basic level. If it makes it all the way into the memory used for displaying stuff you can imagine whats happening to the rest of memory where vital things are stored.

This is just a guess however based on a brief description and my binary assessment of a working computer vs. a broken one.

Bil

naI · May 24, 2009, 03:36 AM

Quote from: Wes on May 05, 2009, 10:28 PM
Have you tried holding down CAPS LOCK when you boot?

Yes.

Quote from: BilHerd on May 23, 2009, 05:55 AM
I'd have to go with cursed... do you have some chicken skulls laying around that we could use for a cleansing?

Seriously if you get garbage characters, especially if they just happen, then something is probably hosed at a basic level. If it makes it all the way into the memory used for displaying stuff you can imagine whats happening to the rest of memory where vital things are stored.

This is just a guess however based on a brief description and my binary assessment of a working computer vs. a broken one.

Bil

Hmm... that's a shame... The idea of malfunctioning memory had occurred to me, but it just didn't make sense, considering that only some programs seemed to be affected. Also, this has only ever happened in 64 mode. I'm certain that plenty of those programs use 64K, but I'm not exactly sure how that works on the C=128 with more total memory and an MMU (so far, I only know a minimal amount of BASIC). I doubt that there's a glitch in the kernel, because, AFAIR, this problem existed both before and after I installed the JiffyDOS kernel replacement.

...Come to think of it.. I must have broken a mirror while the C=128 was in the same room.. But that's just superstition ...right?

Good to hear from you, Bil. That's a nice machine you've got there. It's almost like... A Higher Intelligence.

megabit · May 24, 2009, 11:49 AM

Try running your program in RAM 1. If you have a problem with RAM 0, it may run in RAM 1.

Go to the internal monitor and enter this small program:

.1300 LDA #$40 ;switch to ram 1 with all
.1302 STA $FF00 ; ROMS present
.1305 LDA $D506 ;switch 40-col screen
.1308 ORA #$40 ; to RAM 1
.130A STA $D506
.130D JMP $E24B ;jump to GO64 routine

Save the program to disk:

S"RAM1-64",8,1300,1310

When you are ready to run the program, use the monitor again to load the program to $03F0, the location is common for RAM 0 and RAM 1.

L"RAM1-64",8,03F0

Then type G03F0 and hit return. You will be in 64 mode in RAM 1.

Dan...

naI · May 25, 2009, 03:33 AM

Quote from: megabit on May 24, 2009, 11:49 AM
.1300 LDA #$40 ;switch to ram 1 with all
.1302 STA $FF00 ; ROMS present
.1305 LDA $D506 ;switch 40-col screen
.1308 ORA #$40 ; to RAM 1
.130A STA $D506
.130D JMP $E24B ;jump to GO64 routine

Unfortunately, after I loaded this program numerous times last night, there was no change in behavior. It looks like it just won't work. Is there another register to which I should try loading this? Or would it not matter? Anyway, it doesn't look like RAM 1 makes a difference; I even checked $03F0 in the monitor to make sure the program matched your post.