Thursday, November 27, 2008

A sound idea and Vista kicking you when you're down.

I was fixing some sound issues with Minus4j last night, as I suddenly discovered it was actually pretty broken. If both channels went quite loud and high frequency, it all started to break up - samples too in point of fact. So I spent some time fixing this and its all much nicer, samples sound pretty clean and music in Commando and Monty on the Run are much much nicer.

This then lead me to look at D64 support. I was trying to load TerraNova and it started to work, then didn't. It gets stuck in some odd loop which i think is sample based, but I'm not sure, and I think I have my interrupt flagging wrong. Currently I flag them only when $FF0A is also set, but I believe this is wrong. I think you should always flag them, they just dont kick off an interrupt!

So i thought I'd do some test code on the real machine and see what happens. It was at this point I realised I haven't downloaded anything since I've upgraded (and I use that term losely) to Vista x64. Parallel port access requires a system driver, and under x64 all system drivers must be x64 based. This means my great little 32bit dll which gives me raw access to a parallel port under windows, now no longer works, which in turn means I can no longer download directly to the plus4 - OR carry on with my debugger. FEK!

So I've managed to find a 64bit version of the driver, but its just not working, and now I dont know if thats because the driver isn't working, isn't being found or simply because the parallel port on my machine is set up wrongly. FEK.

So tonight I hope to fix this and test out the interrupt registers a bit more. At the same time, I've started adding D64 support via the Commodore 1551 parallel port registers. This is why turbo loaders dont work on Minus4 as I assume its one of these devices. I used to just intercept calls to the LOAD command, but this is a little better. Anyway, I hope to get basic D64 support in soon although with all the disk turbo loaders around I'm not sure how much use it'll be.

As a little aside.. I was looking at the Minus4sim I started years back. This was a cycle perfect version of Minus4, but I got bored with emulation and mechanic was a little too messy for my likeing. However... C# has some really, REALLY cool constructs for pausing code mid execution, and i think if I ported it over to C#, it would all become VERY elegent and simple to follow. No longer would you have to hold partial states etc. You just pause and resume. So I may play with this at a later date as it would give some very simple code but yield some amazing results. It would also allow me to finally do a fully emulated 1541, which I've been meaning to do for years.

Still mustn't get too side tracked. I have to finish up with Minus4j, then the debugger, then back on to Xeo3.

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