Search found 2434 matches

by TmEE co.(TM)
Tue Jan 17, 2023 12:01 pm
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 863
Views: 768859

Re: New Documentation: An authoritative reference on the YM2612

One thing is that the write itself happens at the end of instruction so the delay really starts then and what happens next depends on what comes after. In the end I gave up trying to optimize access speeds and use IX/IY with YMPORT in them permanently, since I don't use them for anything else due to...
by TmEE co.(TM)
Tue Jan 17, 2023 1:42 am
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 863
Views: 768859

Re: New Documentation: An authoritative reference on the YM2612

I remember needing a larger than normal delay on key on/off registers when I made my sound driver many years ago, the envelope thing you mention is because the 4bits react differently and sometimes one or more won't do same as others and this can dramatically alter the sound. I also remember getting...
by TmEE co.(TM)
Mon Jan 09, 2023 9:09 pm
Forum: Mega/SegaCD
Topic: Thoughts on BIOS modding.
Replies: 2
Views: 353

Re: Thoughts on BIOS modding.

I would do it to my machines just beacuse I don't have or are unlikely to ever gonna have the RAM cart, those extra 24KB will be most welcome lol
by TmEE co.(TM)
Tue May 31, 2022 10:01 am
Forum: Megadrive/Genesis
Topic: Questions About Megadrive Chips/Signal
Replies: 2
Views: 919

Re: Questions About Megadrive Chips/Signal

Z80 bus request and reset come from bus chip, using the single data line that is connected to it. Z80 banker also is done by that chip, one bit at a time. Version register with its many bits comes from the IO chip, and !FDC (MCD presence) and region signals also connect to it. IO chip has all data l...
by TmEE co.(TM)
Fri May 27, 2022 8:46 am
Forum: Video Display Processor
Topic: SMS and SMS mode output levels
Replies: 4
Views: 8743

Re: SMS and SMS mode output levels

I think I made a typo and meant to write CXA output instead. Signal levels are near 1Vpp for full while there. It was so long ago so I am not totally sure anymore. MD VDP RGB DAC output is roughly linear when unloaded indeed, but it is quite high impedance and the loading from the divider will cause...
by TmEE co.(TM)
Mon May 16, 2022 7:01 pm
Forum: Megadrive/Genesis
Topic: VPA Signal in interrupt process
Replies: 7
Views: 1655

Re: VPA Signal in interrupt process

It is driven by 315-5308/5364/5402/5433 and it should be response to FCx pins which also connect to these chips. I don't know any further details though...
by TmEE co.(TM)
Sat Mar 05, 2022 10:24 am
Forum: Hardware
Topic: Decapping more Genesis chips
Replies: 16
Views: 22726

Re: Decapping more Genesis chips

*is excited about future*
by TmEE co.(TM)
Sun Jan 02, 2022 6:49 pm
Forum: Super 32X
Topic: 32X VDP going crazy with my attempts to draw
Replies: 33
Views: 8941

Re: 32X VDP going crazy with my attempts to draw

There is only enough fill rate to cover all of the screen once while using all of the CPU power, due to all the wait states on VRAM access. If you want 60FPS you need to limit amount of stuff that gets drawn, both in area and definitely in overdraw. It is faster to check what has to be drawn and cul...
by TmEE co.(TM)
Thu Sep 23, 2021 1:22 am
Forum: Cartridge
Topic: Change RAM, CRAM from addon
Replies: 2
Views: 5827

Re: Change RAM, CRAM from addon

Cartslot is slave only with no means to do bus mastering (it cannot initiate writes to the console, only receive them) so you'll need software help. One way is to hijack frame interrupt, do your thing in it and then run the original handler, but it might break timing sensitive games.
by TmEE co.(TM)
Sun Sep 12, 2021 1:49 am
Forum: Video Display Processor
Topic: CRAM question
Replies: 1
Views: 2074

Re: CRAM question

CRAM is a physical array of 64 x 9 bits on the silicon, the unused bits in the data port are simply not connected to the actual memory at least as far as writes are concerned. These unused bits can be anything, they simply are ignored when writes are done. For reads I am unsure what will happen, are...
by TmEE co.(TM)
Wed Aug 11, 2021 10:26 pm
Forum: Video Display Processor
Topic: VDP Resolution
Replies: 3
Views: 2789

Re: VDP Resolution

A TV often does what is referred to as the overscan, which means that only some part of the full image gets shown on the physical screen. There is no direct pixel mapping going on and because of this a game is not supposed to put anything in the edges of the screen since they are simply not guarante...
by TmEE co.(TM)
Wed Aug 11, 2021 10:11 pm
Forum: Megadrive/Genesis
Topic: TMSS
Replies: 6
Views: 3759

Re: TMSS

TMSS ROM inside the MD (if present) checks for presence of "SEGA" or " SEGA" at $000100 in your ROM, if found it will boot your ROM. Otherwise it just enters an idle loop and the ROM will not be started and you won't get to see the "produced by...." screen. TMSS ROM has no relation to the $A14000 re...
by TmEE co.(TM)
Tue Aug 10, 2021 8:45 pm
Forum: SGDK
Topic: 68k based PCM Audio mixer for YM2612
Replies: 7
Views: 2863

Re: 68k based PCM Audio mixer for YM2612

You have line and frame interrupts so that is not a problem, though Z80 only gets frame interrupt. Yes, Z80 can do it, and you are supposed to use Z80 for it (and all the sound tasks in general). You cannot send data to Z80 RAM without stopping the Z80 so updating any buffers while also doing playba...
by TmEE co.(TM)
Tue Aug 10, 2021 9:26 am
Forum: SGDK
Topic: 68k based PCM Audio mixer for YM2612
Replies: 7
Views: 2863

Re: 68k based PCM Audio mixer for YM2612

You're in for a big disappointment because the PCM on MD doesn't work anywhere near like it does on the ST. You just have one IO port in the YM that you must manually feed with new data, all timing is up to you as there is no automatic sample fetching and you don't have any regular interrupt to do t...
by TmEE co.(TM)
Mon Aug 02, 2021 4:57 am
Forum: Video Display Processor
Topic: VDP Resolution
Replies: 3
Views: 2789

Re: VDP Resolution

224 vs 240 has 8 pixel borders in top and bottom, but 256 vs 320 is filling the screen horizontally, with non square pixels in 256 (just like Master System and (S)NES stuff. Pixels are longer in the video signal output by VDP compared to shorter ones of 320, there's no really good ways to cleanly ap...