Search found 2415 matches

by TmEE co.(TM)
Fri Apr 09, 2021 9:59 am
Forum: Megadrive/Genesis
Topic: VDP FIFO and DMA questions
Replies: 3
Views: 1614

Re: VDP FIFO and DMA questions

Half lines are part of the video signal, around VSYNC signal. They existed to allow early sync separation circuits to reliably produce a VSYNC pulse using a simple integrator circuit on extracted CSYNC signal. Two halflines make a whole line. The 16 and 17 are Hsync length in the half lines, un pixe...
by TmEE co.(TM)
Fri Apr 09, 2021 3:25 am
Forum: Megadrive/Genesis
Topic: VDP FIFO and DMA questions
Replies: 3
Views: 1614

Re: VDP FIFO and DMA questions

Here is all there is to know about MD video output timings, from my unreleased MD VDP doc. Things are not fully finished around half lines parts, the number lines mean pixels counts during half lines, one number while in sync period, other outside sync. 888aaa999 ones mean pixel patterns during sync...
by TmEE co.(TM)
Sat Apr 03, 2021 10:56 pm
Forum: Super 32X
Topic: Reset and VRES
Replies: 2
Views: 1248

Re: Reset and VRES

I imagine you modify stack to have a new return address prior to exiting the interrupt and probably force caches to be flushed too.
by TmEE co.(TM)
Thu Mar 25, 2021 8:37 am
Forum: Super 32X
Topic: Questions on emulating the 32X
Replies: 14
Views: 2335

Re: Questions on emulating the 32X

Is this the case only when it's the backdrop color (no background/sprites), or when it's the backdrop color OR palette color 0 (from a background or sprite)? VDP never renders color 0 of any palette when drawing BGs and sprites on the screen, it is the backdrop color that is output when a particula...
by TmEE co.(TM)
Wed Mar 24, 2021 10:38 am
Forum: Super 32X
Topic: Questions on emulating the 32X
Replies: 14
Views: 2335

Re: Questions on emulating the 32X

VDP outputs a signal called !YS which is active when nothing/backdrop color is being output, it is present on cartslot along with !HSYNC and !VSYNC signals and 32X uses them for image alignment and composition purposes. There are 3 signals involved in controlling if 32X or MD RGB signal is switched ...
by TmEE co.(TM)
Tue Feb 16, 2021 7:53 pm
Forum: Megadrive/Genesis
Topic: Version Register
Replies: 6
Views: 1501

Re: Version Register

I have only ever seen the chip in Japanese machines, never in EU or US ones. I have the chip transplanted onto an EU VA5/6 board and the region mod changes TMSS behaviour. l_oliveira has some observations done too in past, telling that "SEGA" write is unnecessary when the language setting is in JP i...
by TmEE co.(TM)
Tue Feb 16, 2021 11:48 am
Forum: Megadrive/Genesis
Topic: Version Register
Replies: 6
Views: 1501

Re: Version Register

Right, 315-5402 is special, it shows no TMSS when in JP mode, while TMSS is shown in EN mode. I did notice the freezing problem with TMSS as I tried to dump the ROM when accessing the banking register...

The value is not adjustable externally.
by TmEE co.(TM)
Mon Feb 15, 2021 7:46 pm
Forum: Megadrive/Genesis
Topic: Version Register
Replies: 6
Views: 1501

Re: Version Register

Verison part is hardwired to 0001 on all hardware I have seen (that has TMSS)
by TmEE co.(TM)
Tue Jan 12, 2021 10:51 am
Forum: Megadrive/Genesis
Topic: Discrepency in TMSS ROM Dumps?
Replies: 5
Views: 1823

Re: Discrepency in TMSS ROM Dumps?

Amstrad uses 315-5476 ASIC which has the same TMSS in it as all the other MD2s. Teradrive is the only special one.
by TmEE co.(TM)
Mon Jan 11, 2021 8:11 pm
Forum: Megadrive/Genesis
Topic: Discrepency in TMSS ROM Dumps?
Replies: 5
Views: 1823

Re: Discrepency in TMSS ROM Dumps?

All the TMSS dumps I have done from various chips gave same file that already lingers on the internet. I have not had a chance to try to dump things from VA2 MD2s and I have not tried to dump Genesis3 VA2. MD2 VA4 and Genesis3 VA1 I think I have dumped but I am not sure, it has been 10 years by now ...
by TmEE co.(TM)
Sun Nov 29, 2020 8:06 am
Forum: Megadrive/Genesis
Topic: Megadrive ASIA Configuration
Replies: 2
Views: 2224

Re: Megadrive ASIA Configuration

50Hz + ENG, same as European models.
by TmEE co.(TM)
Sat Aug 22, 2020 5:02 am
Forum: Megadrive/Genesis
Topic: List of every detectable difference in Mega Drive revisions?
Replies: 17
Views: 8422

Re: List of every detectable difference in Mega Drive revisions?

That's something I didn't know, I mainly only commented among the actual consoles (except MD2 VA2, which I would like to get and a VA0 MD1). Discrete YM3438 has longer busy bit cycle from what I remember reading from nukeYKT core notes, compared to 2612 and ASIC which would be another way to detect ...
by TmEE co.(TM)
Fri Aug 21, 2020 5:30 pm
Forum: Megadrive/Genesis
Topic: List of every detectable difference in Mega Drive revisions?
Replies: 17
Views: 8422

Re: List of every detectable difference in Mega Drive revisions?

YM3438 only appeared as a block integrated in the MD2 ASIC, which first appeared in MD1 VA7 (the awful sounding MD1s lol).
by TmEE co.(TM)
Tue Aug 18, 2020 2:56 pm
Forum: Megadrive/Genesis
Topic: List of every detectable difference in Mega Drive revisions?
Replies: 17
Views: 8422

Re: List of every detectable difference in Mega Drive revisions?

Originally I saw it with CRAM yeah, but dedicated test used VRAM DMA. I will dig up the stuff hopefully in not so far future, there's currently bunc hof work stuff getting in the way (retro PC sound hardware stuff)...

I haven't actually ever experienced the DMA bug you describe.
by TmEE co.(TM)
Mon Aug 17, 2020 9:12 pm
Forum: Megadrive/Genesis
Topic: List of every detectable difference in Mega Drive revisions?
Replies: 17
Views: 8422

Re: List of every detectable difference in Mega Drive revisions?

Originally I saw it when I was doing very precise raster effects, where DMA triggering was in two writes to win time, but with Z80 running I noticed that I had failing DMAs every once in a while (in that case palettes didn't get updated). Then I made a specially crafted thing, where I deliberately s...