Search found 2352 matches

by TmEE co.(TM)
Sun May 19, 2019 10:50 am
Forum: Megadrive/Genesis
Topic: Cart Design Questions
Replies: 34
Views: 3476

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: 44
Views: 1246

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: 34
Views: 3476

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: 44
Views: 1246

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: 44
Views: 1246

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: 32
Views: 882

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: 1053

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...
by TmEE co.(TM)
Thu May 02, 2019 6:24 am
Forum: Mega/SegaCD
Topic: Questions on writing a new Mega CD emulator
Replies: 87
Views: 1906

Re: Questions on writing a new Mega CD emulator

Top address byte of DMA transfer is a page register so to say, only the lower two bytes actually increment with each transfer, thus the 128KB pages where transfers take place.
by TmEE co.(TM)
Thu May 02, 2019 6:21 am
Forum: Super 32X
Topic: Using 32x as a 3rd plane, possible?
Replies: 28
Views: 1053

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

68K can certainly draw into the framebuffers but it is probably tens of times slower that SH2 and you can probably forget about things like scrolling etc. since they'll use up a lot of 68K time, every single pixel needs to be manually written to the framebuffers by CPU, there's no hardware blitter. ...
by TmEE co.(TM)
Wed May 01, 2019 8:46 am
Forum: Sound
Topic: Some beginner questions concerning YM2612
Replies: 24
Views: 688

Re: Some beginner questions concerning YM2612

There is no initialization, the attack begins wherever last state left off. Only way to get maximum attenuation is to wait out the envelope, using fastest release to reduce the time needed. Only on chip reset the internal attenuation is at max attenuation, once first note begins all bets are off.
by TmEE co.(TM)
Wed May 01, 2019 3:36 am
Forum: Super 32X
Topic: Using 32x as a 3rd plane, possible?
Replies: 28
Views: 1053

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

Motorola couldn't up the clocks and their chips started to lag behind others (intel, IBM etc.) who were getting faster and faster, their big flagship chips weren't competitive anymore and customers moved to new things. In the end they dropped 68k line and started doing PowerPC instead...
by TmEE co.(TM)
Tue Apr 30, 2019 2:18 pm
Forum: Super 32X
Topic: Using 32x as a 3rd plane, possible?
Replies: 28
Views: 1053

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

68040 and 68060 are the pipelined 68k series CPUs.
by TmEE co.(TM)
Mon Apr 29, 2019 2:15 am
Forum: Sound
Topic: Some beginner questions concerning YM2612
Replies: 24
Views: 688

Re: Some beginner questions concerning YM2612

Most of the info is found in this post and this thread in general : viewtopic.php?p=5716#p5716
by TmEE co.(TM)
Sat Apr 27, 2019 11:13 pm
Forum: Sound
Topic: Some beginner questions concerning YM2612
Replies: 24
Views: 688

Re: Some beginner questions concerning YM2612

Attack is done with reverse logarithmic slope while other things are done with normal logarithmic slopes. The way envelopes progress is tied to couple LUTs, after every certain amount of samples according to one LUT and ADSR settings, a value from another LUT is added to the attenuation value. Attac...