Search found 2359 matches

by TmEE co.(TM)
Tue Jun 18, 2019 9:39 pm
Forum: Sound
Topic: How DAC works ?
Replies: 8
Views: 151

Re: How DAC works ?

YM2612 outputs for one cycle every 6 cycles (one channel time), while YM3438 output at 5 (at least I recall gaps between each channel) of these 6 cycles IIRC. This gives 3438 much better SNR and also makes it need much less amplification and easier filter to get good output level compared to 2612. T...
by TmEE co.(TM)
Mon Jun 10, 2019 6:32 pm
Forum: Mega/SegaCD
Topic: Japanese MegaCD BIOS 1.00C
Replies: 1
Views: 139

Japanese MegaCD BIOS 1.00C

I was given a chance to dump a new Mega CD BIOS, Japanese version 1.00C and here it is :
http://www.tmeeco.eu/SMD/BIOS/MegaCD%20J%201.00C.BIN
Image
by TmEE co.(TM)
Tue Jun 04, 2019 10:16 am
Forum: Mega/SegaCD
Topic: Questions on writing a new Mega CD emulator
Replies: 112
Views: 5305

Re: Questions on writing a new Mega CD emulator

The big filters are for bandwidth limiting and are responsible for the characteristics of the passband ripple and whatever goes on in the stopband. This isn't really useful to model, especially since whatever plays the sound will do its own stuff like that, mangling whatever you did (and you need to...
by TmEE co.(TM)
Wed May 22, 2019 12:39 pm
Forum: Demos
Topic: MD-NICCC - a 3D Mega Drive experience by TiTAN
Replies: 55
Views: 3468

Re: MD-NICCC - a 3D Mega Drive experience by TiTAN

It actually is connected, just on VA0 32X. on VA1 it is replaced with GND connection on the cartridge end. I wonder why...
by TmEE co.(TM)
Wed May 22, 2019 8:18 am
Forum: Demos
Topic: MD-NICCC - a 3D Mega Drive experience by TiTAN
Replies: 55
Views: 3468

Re: MD-NICCC - a 3D Mega Drive experience by TiTAN

Write strobe is passed but in only works from accesses from 68K side, SH2s can only produce read cycles in cart area. I don't know if this is a limitation due to bus management chip or SH2 configuration registers caused problem. You're not supposed to change those registers after initial setup but I...
by TmEE co.(TM)
Tue May 21, 2019 1:50 pm
Forum: Demos
Topic: MD-NICCC - a 3D Mega Drive experience by TiTAN
Replies: 55
Views: 3468

Re: MD-NICCC - a 3D Mega Drive experience by TiTAN

That's good to know, another mod to add to a 32X to make it more useful. Just need to figure out how exactly should overriding stuff work lol
by TmEE co.(TM)
Mon May 20, 2019 9:49 pm
Forum: Demos
Topic: MD-NICCC - a 3D Mega Drive experience by TiTAN
Replies: 55
Views: 3468

Re: MD-NICCC - a 3D Mega Drive experience by TiTAN

Then I remember wrong. I recall that it used one such area that 32X didn't pass through and possibly used it for itself thus SVP cannot run through it but seems only A15xxx range is used by SVP outside normal stuff. But it could just be the DMA latency issue I just read about from your docs. 32X doe...
by TmEE co.(TM)
Sun May 19, 2019 10:50 am
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 40
Views: 4733

Re: Cart Design Questions

You can use !AS to latch the current address for decode purposes etc. I'm not sure if DMA uses it or not though.
by TmEE co.(TM)
Sat May 18, 2019 7:39 pm
Forum: Demos
Topic: MD-NICCC - a 3D Mega Drive experience by TiTAN
Replies: 55
Views: 3468

Re: MD-NICCC - a 3D Mega Drive experience by TiTAN

It can only be used in ranges where VDP doesn't generate it for you such as 800000...9FFFFF. This area is used by 32X and SVP for example. You cannot forcibly override !DTACK since VDP actively drives it on most accesses.
by TmEE co.(TM)
Sat May 18, 2019 7:37 pm
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 40
Views: 4733

Re: Cart Design Questions

You can only drive !DTACK in 800000...9FFFFF range and other ranges (holes in IO ranges) where it isn't generated by VDP for you. In ranges where it is you will cause contention and that's gonna destroy something sooner or later.
by TmEE co.(TM)
Wed May 15, 2019 9:56 pm
Forum: Demos
Topic: MD-NICCC - a 3D Mega Drive experience by TiTAN
Replies: 55
Views: 3468

Re: MD-NICCC - a 3D Mega Drive experience by TiTAN

VDP is what generates the !DTACK *for* 68K. During DMA the 68K is in bus requested state so that signal has no meaning of any sort.
by TmEE co.(TM)
Fri May 10, 2019 7:46 pm
Forum: Demos
Topic: MD-NICCC - a 3D Mega Drive experience by TiTAN
Replies: 55
Views: 3468

Re: MD-NICCC - a 3D Mega Drive experience by TiTAN

One edge puts address on the bus, other edge collects the data. One clock cycle.
by TmEE co.(TM)
Sun May 05, 2019 7:03 am
Forum: Megadrive/Genesis
Topic: I'm officially building a microcode-level 68000 core
Replies: 41
Views: 3112

Re: I'm officially building a microcode-level 68000 core

These names make me think of stuff seen in Visual6502
by TmEE co.(TM)
Fri May 03, 2019 12:41 pm
Forum: Super 32X
Topic: Using 32x as a 3rd plane, possible?
Replies: 28
Views: 2640

Re: Using 32x as a 3rd plane, possible?

Fusion definitely ignores RV bit and always keeps ROM areas same as in MD mode with the exception of vector stuff. For 32X dev you aboslutely need real hardware to do all testing on. When I did more 32X stuff I learned very early on that emulation is way too forgiving and it is super easy to get som...