SpritesMind.Net

Here's some fragments of a recording form my MD2 I took long ago,


Thank you, but... isn't the "ladder effect" supposed to occur on the real YM2612 only? Does your MD2 have the external YM2612 and not the integrated one?

I guess we need a recording from an early MD1. I have one, but no ...

I was going to look at the DAC last, once I've finished examining the other components of the YM2612. I've also noticed the extreme jump between low volume and silence though. I'm sure the answer to that behaviour lies in the DAC.
I confirm that! A very noticeable ladder effect is exist.
http ...

The DRAM used by the Mega Drive VDP is a dual port design, which means that a read and read/write operation can occur at the same time. The VDP probably uses it for reading 16 bits of data on one cycle, writes however can occur only in 8 bit cycles.

Nemesis wrote: I'm not really sure how much immediately useful info a decap will give us, but it'll be fun.

The first component I would examine is the DAC.

Cool, thanks for the info!

Any access will lock up the system

This is not very specific, as you mentioned earlier, the Z80 apparently doesn't lock up. So, does Z80 access to VDP registers lock up the 68k? Does the VDP accept Z80 accesses? What role could the SMS mode play here in this scheme?


, and Z80 isn't very ...

What happens when the Z80 accesses VDP registers in this state? Could the Z80 somehow set up a working display either before or after the 68k is locked?