Multiface II - How to use successfully?

[Lomax]

I've had a bit of a play around with the Multiface II but cannot get saves to load again. I'm using it so that I can save my progress in games like Jet Set Willy.

My machine is an Amstrad CPC 6128 with a Gotek (running HxC firmware) instead of the FDD

Here's my procedure:
1. I run Jet Set Willy, start a new game and play for a while
2. Hit the Stop button, screen colours change and distort and the Multiface II menu appears
3. Choose Save, enter a file name, choose Disc (Program is selected). A series of files are save to disc.
4. Choose Return, and the game continues as normal (screen colours are restored (more or less) to their correct state).
5. Turn off and back on the Amstrad using it's switch
6. Run the first of the save files that is now on disc. The drive operates as if loading something for a while and then the screen appears as it was in step 2 (discoloured and distorted). The drive continues operating for a while.
7. Video output ceases (i.e. not a black screen, but no signal). Using the Reset button on the multiface resets the Amstrad OK.

What am I doing wrong? Are these units a bit hit-and-miss in-so-far as what can be successully saved and re-loaded?

[Longshot]

Why did you create a new thread on the multiface?

The multiface is not able to restart some programs for various reasons.
When you press the stop button, the rom of the multiface is connected between 0000 and 1FFF, and its ram between 2000 and 3FFF and an NMI interrupt occurs.
In other words, the Z80A saves the address where the PC was when you press the button, and jumps to #0066 (in the rom of the multiface2)
But if the stack is in the area of ​​the ram of the multiface when it is connected (when you press STOP), the return address will not be written in the CPC ram but in the ram of the multiface. I have not checked if the cartridge handles this situation well, but it is a possibility.

Also, the multiface can not read the registers of the circuits like the gate array or the crtc because some of these registers are read only.
In fact, it "copies" the registers when the CPC makes OUTs to modify these registers.
But the filtering is too precise because the multiface uses all the bits of the IO address.
But on the CPC, you can assign multiple circuits at the same time depending on each bit in the IO address
Say otherwise, you can hide to the multiface the modification of the records of the CRTC, but also affect, through the "standard" registers, values ​​able to crash the CRTC, or put all the inks in black for example.

The best way to know what's wrong is to look the data saved in the first file.
Can you post this file here ?

[Lomax]

Why did you create a new thread on the multiface?

My apologies, my other thread was asking about addressing, I thought I’d post another that was more specific to what I’m doing with the Multiface. OMG, I’ve just realized who you are!


I know nothing about low level addressing, etc, but I’m trying to get up to speed as fast as I can. Any relevant reading material will be appreciated.

The best way to know what's wrong is to look the data saved in the first file.
Can you post this file here ?

I will do shortly.

[Lomax]

I've attached the first of the save files. Let me know if anything else is required. Also please let me know the tools you use to probe it.

[Longshot]

In the attached dsk, you will find a program (run "razram") that you can run before starting the game, and that will erase the banks, because it seems that Multiface detects that the game occupies 128kb, which is rather strange for "jet set willy" game.

You can also run the "Analyse" program, which clearly displays some of the data contained in the "Save.bin" file.(chip registers, z80 registers)

Can you tell if you have 8 saved files again when you start "razram" before loading the game (and then saved with MF2).
It's accessory, but with "antimv12.eng", you can create a loader without needing the multiface anymore.