Wednesday, 30 April 2014

MVS Adapters and a world first???

My colleague kindly finished soldering the MVS adapters, though I suspect it irked him that my soldering (arguably) wasn't up to scratch. I certainly didn't see anything wrong with it, and I haven't really had any problems with it in the past... but I can't complain considering he saved me the task!

So, I'm happy to report that the MVS adapter also works fine - that's 2 from 2!!! It's a bit tight on the horizontal 1-slot - in fact it does interfere with a cap on my MV-1FZ - and we're likely to run into more problems once the programmer/analyser board is connected, so I suspect I'll be repairing the multi-slot PCB's that I bought for this very eventuality.

What I was really keen to test, however, was swapping the two cartridge adapters for each system, to see if they would at least boot on the other hardware.

The obvious first choice was an MVS cartridge in the AES - there are several converter boards out there - and I thought it would be the more likely of the two configurations to work. Well, unfortunately that wasn't the case; my UNIBIOS-enabled AES system simply displays the same blank white screen that you get when you have no cartridge inserted. Quite disappointing. Also unfortunate was the fact that I had left my one-and-only Neo Geo controller at home, and I had no way to tweak UNIBIOS settings to see if I could coax it into working. So that will have to wait until another day.

EDIT: I just tried it again - and it worked!!! I guess I wasn't holding my tongue right!?!

So it was without much optimism that I plugged the AES cartridge into the MVS board and switched it on. Much to my surprise - no to mention delight - I was greeted with a mess of non-graphics that was none-the-less unmistakenly the rotating NEO-GEO logo, and then the FIX layer text appeared!!!

An AES cartridge running on an MVS motherboard

Not long after that, the demo of Fatal Fury 2 started running with the FIX layer intact and random data for the sprites (although in theory I would have expected fully transparent pixels, since I'd grounded the AES sprite data pins on the adapter). But I'll take what I got!

EDIT: The MVS sprite data lines are actually not connected (floating) so that would explain the random sprite data. OTOH the MVS cartridge in the AES system has the grounded serial sprite bus and I do indeed see black/transparent pixels on that system. So all good!

AES Fatal Fury 2 - all working but for random sprite data

Regardless, this is a very promising result, and has me wondering if this is indeed the first time anyone has ever run an AES cartridge on an MVS motherboard? Not that it is particularly useful - it's merely a by-product of my design - as it simply isn't possible (according to my limited analysis) to have the serial sprite data from the AES cartridge re-combined as parallel data, only to be re-serialised internally by the MVS hardware with the correct timing.

An AES cartridge plugged into an MV-1FZ motherboard

I'll therefore return to the issue of the MVS->AES adapter as soon as the opportunity permits with a renewed expectation that it should actually just work.

Finally, to return to the indecision I expressed in my last post; I've decided to keep my prototype flash cartridge as simple as possible, and stick to the original plan of using flash devices that must be programmed via the programmer PCB. I figure that it's adequate for my requirements in the short term, and more important that I maintain the momentum on the project.

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