RAM expansion cross-talk issues (split from: Bitshifter's Z-code interpreter)

[Mike]

I wonder if I'm initiating things correctly. I'm using the MEGA-CART and doing a "normal reset", and choosing the option VIC 32 +3K. Maybe I have some bad RAM?

I made a reply in the other thread where you asked about dragos' RAM/ROM cartridge. This one definitely wouldn't work as it doesn't provide "true" +35K RAM (actually it produces crosstalk between the +3K and BLK5 "by design").

You can check the +32K +3K configuration of Mega-Cart the same way like I wrote to mrr19121970 earlier in the thread:

You can simply check with my CGA panning viewer. When it works, you have the +35K RAM. When it crashes or shows a wrong display (provided you didn't input a wrong file name), you either don't have +35K but just +32K, or you have crosstalk between RAMx or BLKx - unintended or intended by double use of a RAM chip a.k.a. "no-one needs +32K and +3K simultaneously".

Emphasis added (with regard to dragos' cartridge).

Please report back what you found out.

[ral-clan]

I will test your CGA panning viewer.
Alternatively, I have a switch-able 6 port expander board and all the necessary RAM expansion cartridges., perhaps that would be an alternative if the MEGA-CART proves to be the problem.

[ral-clan]

Okay, so I think we've found the problem. The Mega-Cart in 35K+3K mode displays the pictures incorrectly as such:

CECILE:

PCPAINT1:

So...I guess that means the Mega-Cart does not function as a proper 35K + 3K expansion?

Alternatives? I do have the UltiMEM (really a VIC-MIDI). Not sure how to use it as 35K +3K expander, or even if it can be.

I also have this Cardco 6-slot expander:

[Mike]

First of all, it's either +32K+3K or +35K RAM, not "+35K+3K" we're talking about here.

I'm just mentioning it, because you use "+35K+3K" three times in your preceding post - and I want to avoid confusion with another actually existing RAM config that adds *another* 2K in I/O2 and I/O3 to the +35K.

That being said, you have troubles with your setup. It need not necessarily be your Mega-Cart, it could also be issues with the cartridge port of that VIC-20 or, even worse, something with the VIC-20 circuitry itself. Besides trying it with VIC-MIDI, do you have another VIC-20 you could cross-check this way?

In any case, the VIC-MIDI *is* capable of the +35K RAM config.

Tokra's "Ultimem RAM-Expansion Chooser" (link) also works with VIC-MIDI (well, it should) - choose option 2 for a start.

[ral-clan]

First of all, it's either +32K+3K or +35K RAM, not "+35K+3K" we're talking about here.

I'm just mentioning it, because you use "+35K+3K" three times in your preceding post - and I want to avoid confusion with another actually existing RAM config that adds *another* 2K in I/O2 and I/O3 to the +35K.

Oh....okay, I see my error now. Obviously I need to re-read these messages several times, as my glancing through them is not allowing me to absorb the salient points properly.

So....the option I was choosing from the Mega-Cart was "32K + 3K". It didn't work. I will try the Ultimem.

In any case, the VIC-MIDI *is* capable of the +35K RAM config.

Tokra's "Ultimem RAM-Expansion Chooser" (link) also works with VIC-MIDI (well, it should) - choose option 2 for a start.

Okay, sounds like that's how I need to proceed then. WIth the VIC-MIDI / Ultimem. The VIC-MID only has 128K (or 512K?) not the full 1MB that the real Ultimem has....so hopefully Tokra's RAM chooser will work.

EDIT: On closer examination, I don't think I want to try the RAM chooser by TOKRA. I opened the ZIP file and realised it's not a loadable utility - it's a flash-able image for the flash ROM of the UltiMEM. If I use that on my VIC-MIDI I will erase the built in flashed MIDI software of the unit.

I will have to find a way to activate the onboard RAM with a POKE.

[tokra]

Oh....okay, I see my error now. But the reason I was writing "32K +3K" is that that is what the menu in the Mega-Cart actually says. It's not a typo on my part. I didn't realise what I really needed was 35K +3K.

Nooooooooh (Darth Vader-style). There is no such thing as 35K +3K. You only need 32K + 3K (= 35K expansion total)

I will have to find a way to activate the onboard RAM with a POKE.

http://sleepingelephant.com/denial/wiki ... le=UltiMem

You can find the POKEs there. Either 37K or 35K is fine.

[ral-clan]

Oh....okay, I see my error now. But the reason I was writing "32K +3K" is that that is what the menu in the Mega-Cart actually says. It's not a typo on my part. I didn't realise what I really needed was 35K +3K.

Nooooooooh (Darth Vader-style). There is no such thing as 35K +3K. You only need 32K + 3K (= 35K expansion total)

I will have to find a way to activate the onboard RAM with a POKE.

http://sleepingelephant.com/denial/wiki ... le=UltiMem

You can find the POKEs there. Either 37K or 35K is fine.

I edited my message above as I finally understand my compound errors in reading these threads too quickly. No more 35K+3K anymore. I promise!

[ral-clan]

Well, good news.

With the UltiMEM, both ZORK and the Mike's panning viewer work.
So I guess that the Mega-Cart's 32K+3K (35K) is not functional?

As for beta-testing this ZORK 32-column version:
I was able to load both Zork I and Zork II (didn't try Zork III).
I moved around a bit and was able to explore.
I was able to save and restore a game.

[orion70]

Strange... I use it with TNT's implementation of Infocom adventures, and don't see any problem

[ral-clan]

Strange... I use it with TNT's implementation of Infocom adventures, and don't see any problem

Yes, I can confirm that TNT's port works with the Mega-Cart, but just double checked and the same Mega-Cart RAM settings do not work with Bit-shifter's 32 column port.

Maybe it has something to do with the extra RAM needed for the 32-column mode. Perhaps the TNT version only uses the 32K and not the extedended 3K.

[Mike]

TNT's port only requires +32K.

Maybe it has something to do with the extra RAM needed for the 32-column mode.

The different display mode has not much to do with the extra RAM requirements of Bit Shifter's interpreter. A different implementation of the data structures and another choice how much of the story is supposed to be buffered has a much larger impact on the RAM needed. You can't go below a certain amount of buffering, otherwise the adventure would not stop accessing the disk drive, and this would slow down the game down to unplayability.

At least the culprit has been found. Maybe it's an ultra-rare case of cross-talk with your pair Mega-Cart+NTSC VIC-20 and AFAIK this has otherwise mainly been reported with FE3+NTSC VIC-20.

Could you please try out the +3K RAM expansion of your Mega-Cart on its own? At start-up, you should of course see the "6655 BYTES FREE", and ...

[ral-clan]

Could you please try out the +3K RAM expansion of your Mega-Cart on its own? At start-up, you should of course see the "6655 BYTES FREE", and ...

Yes, I do see 6655 BYTES FREE with the Mega-Cart only enabling 3K expansion.

[Mike]

... I was about to find a usable candidate to check the +3K expansion, but zimmers.net decided to ask me for login multiple times and didn't accept anonymous login. For whatever reason (it just happens sometimes).

Anyhow, I was wrong in one detail, actually TNT's interpreter also requires +35K (as stated somewhere earlier in this thread). In that case I can only suspect, that TNT did not store 'too critical' data into the suspected cross-talk regions, so it 'seems' to work. Presumably, you'll still get crashes later on while playing. This is the kind of bugs that doesn't necessarily reveal by just a few minutes of playtesting. If the wrongdoing RAM areas aren't used at the moment, you won't see any problems, but they appear as soon as they're used for processing.

My CGA viewer exercises the whole extra RAM thoroughly. That's the reason any misbehaviour will pop up immediately.

As I said, try to check your Mega-Cart with another VIC-20. Chances are it still works there.

[ral-clan]

Mike, you are right.

I tried with another VIC-20 and the 32-column ZORK port functions with that VIC-20.
So....now I need a mem-test utility. I'm moving this discussion to another thread:
http://sleepingelephant.com/ipw-web/bul ... f=1&t=8923

Any suggestions on a RAM test utility (please comment in that thread) would be appreciated.

[Bit Shifter]

Well, good news.

With the UltiMEM, both ZORK and the Mike's panning viewer work.
So I guess that the Mega-Cart's 32K+3K (35K) is not functional?

As for beta-testing this ZORK 32-column version:
I was able to load both Zork I and Zork II (didn't try Zork III).
I moved around a bit and was able to explore.
I was able to save and restore a game.

I'm glad, that you've found the problem.

My interpreters uses the 3K expansion for the storage of the track/sector table for all blocks of the sequential story file.
Also the Z-machine runtime stack and one page of variables are loacted there. So any memory corruption in this area will lead to an internal error very soon.