Search found 2443 matches
- Sat Apr 03, 2021 10:56 pm
- Forum: Super 32X
- Topic: Reset and VRES
- Replies: 2
- Views: 7872
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.
- Thu Mar 25, 2021 8:37 am
- Forum: Super 32X
- Topic: Questions on emulating the 32X
- Replies: 14
- Views: 245489
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...
- Wed Mar 24, 2021 10:38 am
- Forum: Super 32X
- Topic: Questions on emulating the 32X
- Replies: 14
- Views: 245489
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 ...
- Tue Feb 16, 2021 7:53 pm
- Forum: Megadrive/Genesis
- Topic: Version Register
- Replies: 6
- Views: 13724
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...
- Tue Feb 16, 2021 11:48 am
- Forum: Megadrive/Genesis
- Topic: Version Register
- Replies: 6
- Views: 13724
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.
The value is not adjustable externally.
- Mon Feb 15, 2021 7:46 pm
- Forum: Megadrive/Genesis
- Topic: Version Register
- Replies: 6
- Views: 13724
Re: Version Register
Verison part is hardwired to 0001 on all hardware I have seen (that has TMSS)
- Tue Jan 12, 2021 10:51 am
- Forum: Megadrive/Genesis
- Topic: Discrepency in TMSS ROM Dumps?
- Replies: 5
- Views: 44639
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.
- Mon Jan 11, 2021 8:11 pm
- Forum: Megadrive/Genesis
- Topic: Discrepency in TMSS ROM Dumps?
- Replies: 5
- Views: 44639
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 ...
- Sun Nov 29, 2020 8:06 am
- Forum: Megadrive/Genesis
- Topic: Megadrive ASIA Configuration
- Replies: 2
- Views: 8950
Re: Megadrive ASIA Configuration
50Hz + ENG, same as European models.
- Sat Aug 22, 2020 5:02 am
- Forum: Megadrive/Genesis
- Topic: List of every detectable difference in Mega Drive revisions?
- Replies: 17
- Views: 240721
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 ...
- Fri Aug 21, 2020 5:30 pm
- Forum: Megadrive/Genesis
- Topic: List of every detectable difference in Mega Drive revisions?
- Replies: 17
- Views: 240721
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).
- Tue Aug 18, 2020 2:56 pm
- Forum: Megadrive/Genesis
- Topic: List of every detectable difference in Mega Drive revisions?
- Replies: 17
- Views: 240721
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.
I haven't actually ever experienced the DMA bug you describe.
- Mon Aug 17, 2020 9:12 pm
- Forum: Megadrive/Genesis
- Topic: List of every detectable difference in Mega Drive revisions?
- Replies: 17
- Views: 240721
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...
- Sun Aug 16, 2020 4:16 pm
- Forum: Megadrive/Genesis
- Topic: List of every detectable difference in Mega Drive revisions?
- Replies: 17
- Views: 240721
Re: List of every detectable difference in Mega Drive revisions?
DMA doesn't fail and load garbage, it is outright cancelled, the transfer does not happen and you can measure the time won from that and determine if DMA happened or not, or read VRAM instead.
- Sat Aug 15, 2020 1:40 pm
- Forum: Megadrive/Genesis
- Topic: List of every detectable difference in Mega Drive revisions?
- Replies: 17
- Views: 240721
Re: List of every detectable difference in Mega Drive revisions?
There is some small difference in timing of Z80 bus crossings between MD1 VA0...MD2 VA3 (MD1 chipsets, 315-5487/5660/5700/5708), MD1 VA4/Genny3 VA1(515-5960) and Genny3 VA2(315-6123). No clue about MD2 VA2.x with 315-5685/5786, I have none to play with. I was exploring what happens when DMA was done...