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PostPosted: Mon Mar 20, 2017 9:43 am 
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anyone working on a genesis hdmi mod not the one reviewtechusa was working on?


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PostPosted: Tue Mar 21, 2017 8:21 am 
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You can probably get a retron 3 or 5 which plays Sega Genesis and outputs HDMI. But I don't see a need considering that the Genesis only had a 320x224 resolution.


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PostPosted: Tue Mar 21, 2017 8:44 am 
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The problem with the Retron is that it uses emulation. Not good for development, because of accuracy and the fact that Flash carts don't work on it at all. You may also have problems playing carts not yet on the system's database (homebrews, for example).

The problem with old consoles with new TVs is not the resolution, but the fact that TV usually do a really crappy job out of interpreting the non-standard video signals old consoles normally output. This results in problems with color, frame rate, interlacing... If you never noticed that, you didn't look hard enough.


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PostPosted: Tue Mar 21, 2017 8:46 am 
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DementedPurple wrote:
You can probably get a retron 3 or 5 which plays Sega Genesis and outputs HDMI.

How compatible is the RetroN 5 with Sega CD games, Virtua Racing (which uses the SVP), Team Player games, 4-Way Play games, Codemasters J-Cart games, and 32X games? And, as tokumaru mentioned, anything recent.

DementedPurple wrote:
But I don't see a need considering that the Genesis only had a 320x224 resolution.

HDMI improves compatibility with TVs purchased in the past decade.
In this post, Rahsennor wrote:
I recently discovered that my Toshiba 40TL900 LCD TV silently disables "game mode" when fed [composite video, giving] 200-300 ms of lag

In this post, Light-Dark wrote:
Some modern TV's don't even have composite video anymore.

In this post, Rahsennor wrote:
I just tested my old Samsung UA32EH5006. It doesn't support 240p


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PostPosted: Tue Mar 21, 2017 9:57 am 
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If you were to do it, I don't think that the 32X would work with it because it requires AV signal form the genesis to be hooked up to it.


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PostPosted: Tue Mar 21, 2017 10:17 am 
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If we want to talk about digital Genesis video, it'd be great to do that. A pixel bus snooping solution would be difficult, but not impossible.

VDP register $0C bit %00010000 enables the 8-bit pixel bus output. This bus gives us a 6-bit index into the color ram (CRAM), as well as shadow/highlight status. This is similar to the EXT bus on the 2C02 PPU, except we don't have to do any intercepts to infer a missing fifth bit.

The problem is snooping palette writes. Capturing writes done with simple CPU-->VDP writes are not hard. Many games use DMA to transfer colors, though, so the challenge becomes complicated. We must snoop writes to the VDP to 1) determine that a DMA to CRAM is being set up, 2) recognize that the DMA has begun, and 3) accurately capture palette data being written during DMA.

CRAM is internal to the VDP, otherwise this would be extremely easy. Since it's not accessible, a cycle-accurate DMA controller must be replicated, and what other internal state of the VDP it relies on is unknown to me. That is the challenging bit.

tepples wrote:
HDMI improves compatibility with TVs purchased in the past decade.

In addition, it doesn't look like dogshit.


Last edited by mikejmoffitt on Tue Mar 21, 2017 10:18 am, edited 1 time in total.

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PostPosted: Tue Mar 21, 2017 10:18 am 
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DementedPurple wrote:
If you were to do it, I don't think that the 32X would work with it because it requires AV signal form the genesis to be hooked up to it.

tepples was just being funny... none of the things he mentioned work and he knows that. About the 32X in particular, the video cable is a very minor problem compared to the fact that the Retron 5 simply dumps data from cartridges for play on its built-in emulators. It's not a console, it's just an emulator box + cartridge dumpers. After a cartridge is dumped, it's useless, and any extra hardware that is present in things like the 32X or the Everdrives is never used.


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PostPosted: Tue Mar 21, 2017 10:24 am 
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tokumaru wrote:
DementedPurple wrote:
I don't think that the 32X would work with it because it requires AV signal form the genesis to be hooked up to it.

tepples was just being funny... none of the things he mentioned work and he knows that.

Actually I didn't know that. It would be theoretically possible for an emulator-based console to emulate the 32X, SVP, or multiplayer accessories after dumping the cart, and even emulate a Sega CD if an optical drive is plugged into a USB port. The hard problem would be making an HLE BIOS.


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PostPosted: Tue Mar 21, 2017 10:34 am 
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mikejmoffitt wrote:
A pixel bus snooping solution would be difficult, but not impossible.

Would that be necessary, though? I thought all Sega machines had easily accessible RGB video (which is encoded into composite by a separate chip) that could be used to generate pretty clear HMDI video, no? Specially considering that the genesis uses only 3 bits per channel, it should be easy to reconstruct the digital signal, shouldn't it?

tepples wrote:
It would be theoretically possible for an emulator-based console to emulate the 32X, SVP, or multiplayer accessories after dumping the cart, and even emulate a Sega CD if an optical drive is plugged into a USB port. The hard problem would be making an HLE BIOS.

True, any special hardware that has been replicated into the emulator could be used to make it seem like the peripherals are working as expected, but I don't think they'd go through the trouble of figuring out a hardware setup to support the Sega CD. Can a 32X cartridge be dumped from the MD side?

Anyway, why would you go through all this trouble if you can just connect your laptop computer to your TV and emulate anything you want? If emulation is good enough for you, A pair of good USB controllers is all you need to have a better experience than what the Retron can give you.


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PostPosted: Tue Mar 21, 2017 10:44 am 
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tokumaru wrote:
mikejmoffitt wrote:
A pixel bus snooping solution would be difficult, but not impossible.

Would that be necessary, though? I thought all Sega machines had easily accessible RGB video (which is encoded into composite by a separate chip) that could be used to generate pretty clear HMDI video, no? Specially considering that the genesis uses only 3 bits per channel, it should be easy to reconstruct the digital signal, shouldn't it?


It might be easy enough, so long as the captures are clocked by MCLK or some reliable division of it. Since the Genesis can do a pixel clock of MCLK/4 (H40) or MCLK/5 (H32), capturing at MCLK might be easiest. Even if it's only 3 bits per channel, with S/H you can get up to 12 different luminance levels, so that must be accounted for.


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PostPosted: Tue Mar 21, 2017 10:55 am 
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mikejmoffitt wrote:
with S/H you can get up to 12 different luminance levels, so that must be accounted for.

Oh yeah, I did think of the shadow/highlight effects but didn't know how much they could affect the colors. Do you think a full reconstruction of the digital picture is possible even when those modes are used?


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PostPosted: Tue Mar 21, 2017 10:59 am 
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tokumaru wrote:
Can a 32X cartridge be dumped from the MD side?

Yes. 32X carts are normal Genesis carts except that their ROM needs to be 80 ns or faster.

tokumaru wrote:
Anyway, why would you go through all this trouble if you can just connect your laptop computer to your TV and emulate anything you want?

This requires either ownership of a laptop whose video output is compatible with your TV or willingness to purchase and maintain an additional desktop PC to put next to the TV. (Older laptops may include VGA but not DVI-D or HDMI out, and some TVs include HDMI in but not VGA in.) Another advantage of an emulator running on a dedicated device is that it's likely to have less latency than an emulators running on a PC with a full-featured window system. But the advantage of an authentic console over any popular emulator is that it reproduces all original bugs, which is helpful for someone testing a game not yet released. Or are Genesis emulators as accurate as higan yet?


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PostPosted: Wed Mar 22, 2017 5:45 pm 
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A brazilian guy seems to have succeeded.
He doesn't show how he did it, and he's using a portable MegaDrive (called MDPlay) inside the original MegaDrive.


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PostPosted: Wed Mar 22, 2017 7:49 pm 
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Fisher wrote:
he's using a portable MegaDrive (called MDPlay)

Well, that sucks! Have you ever heard the sound in those things? Are those things even actual MD hardware or just an emulator that can't even use cartridges?


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PostPosted: Wed Mar 22, 2017 10:19 pm 
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Discussion elsewhere on the internet seems to think that they are actually 68k based, but ... not very accurate otherwise.


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