Search found 2441 matches

by TmEE co.(TM)
Mon Dec 09, 2019 10:29 pm
Forum: Megadrive/Genesis
Topic: M68K Bus Control and Vdp
Replies: 26
Views: 42706

Re: M68K Bus Control and Vdp

68K duplicates high and lwo bytes during 8bit writes (i.e $12 is $1212 on the bus). Reads are aways 16bit and CPU internally chooses which half to use depending on address.
by TmEE co.(TM)
Tue Nov 26, 2019 1:31 am
Forum: Tools
Topic: Aseprite Mega Drive Digitizer
Replies: 19
Views: 34970

Re: Aseprite Mega Drive Digitizer

Computer composhit output would look nothing like the MD output (i.e near complete lack of various artifacts) and you still have the problem of non-linear level ramp that most emulators and tools don't treat right from what I know ( http://gendev.spritesmind.net/forum/viewtopic.php?f=22&t=2188 ). Th...
by TmEE co.(TM)
Mon Nov 18, 2019 9:42 pm
Forum: Megadrive/Genesis
Topic: Noob questions: DEFINITIVE info about Z80 BUSREQ, RESET?
Replies: 28
Views: 32608

Re: Noob questions: DEFINITIVE info about Z80 BUSREQ, RESET?

I haven't had any issues by doing a shorter than 192 cycle reset, but I always explicitly zero out all the YM registers and it seems internal state is also fine.
by TmEE co.(TM)
Fri Nov 15, 2019 12:53 pm
Forum: Megadrive/Genesis
Topic: DMA and FIFO
Replies: 11
Views: 15080

Re: DMA and FIFO

68K User manual suggests it is based on bus cycles rather than instruction cycles, I got the impression you can get the bus while an instruction is still halfway done. The processor asserts BG as soon as possible. Normally, this process immediately follows internal synchronization, except when the p...
by TmEE co.(TM)
Thu Nov 14, 2019 12:48 am
Forum: Video Display Processor
Topic: Upload speed on display time
Replies: 2
Views: 7518

Re: Upload speed on display time

There's 16 or 18 access slots spread around one line during rendering, depending on 256 or 320 pixel mode, each capable of accepting one byte so 16 or 18 bytes are possible to transfer in best case during a line. 4x 68K cycles is 3.5 pixels, these access slots come in triplets that are 16 pixels apa...
by TmEE co.(TM)
Sun Oct 27, 2019 3:33 pm
Forum: Cartridge
Topic: Designing MD sdcard flashcart for fun, advice?
Replies: 37
Views: 49535

Re: Designing MD sdcard flashcart for fun, advice?

If it is a proper NOR flash it'll take more than 100k writes before the flash fails. Overall the idea looks doable but I'm not sure if you can cleanly supply NOPs to the 68K and later get it execute something more useful. If I were you I'd pull !MRES low (this signal you can drive yourself, but only...
by TmEE co.(TM)
Thu Oct 03, 2019 7:18 pm
Forum: Controls
Topic: New device letters
Replies: 20
Views: 37990

Re: New device letters

Ok, so you support the Saturn stuff in your game ? How would the MD port pins be connected to the Saturn port ? I'm not sure any standard exists...
by TmEE co.(TM)
Sun Sep 29, 2019 11:42 am
Forum: Controls
Topic: New device letters
Replies: 20
Views: 37990

Re: New device letters

Use lowercase letters too not just uppercase ones, or perhaps just set the top bit to show it is saturn peripheral and not MD.
by TmEE co.(TM)
Mon Sep 23, 2019 5:22 pm
Forum: Demos
Topic: Hyrule in Megadrive/Genesis
Replies: 12
Views: 17818

Re: Hyrule in Megadrive/Genesis

Atmosphere of mars is just incredibly thin, roughly 100x thinner than earth. If it was 100x denser you could even breathe it for a limited amount of time, while there's possibly enough oxygen to sustain you, there's far too much carbon dioxide and you will get a CO2 poisoning from it. The thiness al...
by TmEE co.(TM)
Tue Sep 10, 2019 4:43 pm
Forum: Hardware
Topic: Making Light gun for LCD TV
Replies: 45
Views: 93637

Re: Making Light gun for LCD TV

Composhit is always available, even if one uses RGB. In a proper cable the composhit line is used for sync info for example and also acts as fallback when TV isn't supporting RGB via the SCART. It is also trivial to get luminance info out of both composhit and RGB, and sync you always have side by s...
by TmEE co.(TM)
Sun Sep 08, 2019 1:23 am
Forum: Megadrive/Genesis
Topic: Megadrive was always the answer
Replies: 22
Views: 33101

Re: Megadrive was always the answer

Faster CPUs, more RAM and just enhancing VDP and sound is far more useful and much more doable... getting the two sides share single cart is not going to happen more or less though just adding second VDP (and not doing DMA with it) can work out to some extent. It does take a significant FPGA to fit ...
by TmEE co.(TM)
Fri Sep 06, 2019 10:58 pm
Forum: Megadrive/Genesis
Topic: Megadrive was always the answer
Replies: 22
Views: 33101

Re: Megadrive was always the answer

FPGAs are the only solution, and stuff where you can fit substantial amount of things are easily 50€ a chip (but some simpler stuff can be done with the cheap 20€ chips), and you still need various other parts such as DACs, memories, connectors and also plastic, assembly and distribution. What is yo...
by TmEE co.(TM)
Fri Sep 06, 2019 1:50 pm
Forum: Megadrive/Genesis
Topic: Megadrive was always the answer
Replies: 22
Views: 33101

Re: Megadrive was always the answer

I have already explored this sort of stuff, the hardware part is actually easy and not a huge challenge, but it will be incredibly difficult to keep the costs sane even when I used cheapest parts and nobody will pay price of a modern game console for another 32X essentially, which will only ever see...
by TmEE co.(TM)
Mon Sep 02, 2019 11:31 am
Forum: Megadrive/Genesis
Topic: Sega Tech Docs archive
Replies: 26
Views: 309182

Re: Sega Tech Docs archive

Both links are same...