MiSTer FPGA Forum

Hello all,

I'm new to the MISTer project and after an unsuccessful first try with it I want to check all options before getting my hands with one of this systems.

I've seen some mentions about the use of dual ram. I know that at the moment the only official core supporting dual ram is the PSX and that, in fact, it only helps with half a dozen of games that had 24bit audio. Apparently with single ram there's a very very slight delay with audio there. Also, the new Saturn core is been developed both for dual and single ram MISTer. I don't know if both options will get fully developed or if there's a technical reason for needing dual ram for Saturn or maybe a future project (CPS-3, 3DO... ).

My question is, do you people think I should bet on dual ram? Do you think it will be mandatory for some games or cores?

I now is a question about the future of the project but I would love to read your thoughts and recommendations.

Thanks!

Right now, no you don't need dual-RAM. The Saturn core is making incredible progress and it does not look like dual-RAM will be necessary but that's not a certainty. There is still a lot to be implemented so don't take that as gospel. As Playstation goes, it's really unnecessary; there's an edge-case wherein audio can be imperceptibly late but I've yet to see it in the wild or reproduced in any meaningful way.

My gut tells me CPS3 won't, 3DO who knows (if and when anyone picks that up), Jaguar quite probably (if it is even possible)? I think the developers are really pushing the limits of the DE10-Nano and systems beyond the fifth generation start getting orders of magnitude more complicated and start getting out of reach from a memory bandwidth perspective for presently affordable, off-the-shelf FPGAs.

Tldr; I wouldn't worry about dual-RAM.

Today I wouldn´t bother about dual RAM. We´ll see in the future though.

You wouldn't use it now, and it'll be easy enough to add later on, so I wouldn't personally buy a second stick yet.

Malor wrote: ↑Sun Oct 23, 2022 5:23 pm You wouldn't use it now, and it'll be easy enough to add later on, so I wouldn't personally buy a second stick yet.

I'm a little confused about what's needed for the dual ram. Obviously a second ram stick but something more as the Digital I/O board or that is not needed at all?

You only need double SDRAM boards for testing unfinished/unstable cores; some of them require dual SDRAM before they get optimized enough to run with just one - or even without it entirely
Basically all the devices a MiSTer is able to replicate - so far at least - only had a few megabytes of RAM, thus one SDRAM board should be all you need.

The two SDRAM boards are meant to be installed directly on the DE10 nano connectors, you don't need an I/O board for that.
If you need an I/O board, only the digital one is shaped in a way to expose both the GPIO connectors of the DE10 nano (with an analog I/O board you can only fit 1 SDRAM).
If your have 1 SDRAM board, as it's usually the case, you can use either the analog or the digital I/O board - if you have any use for them, that is.

PhDTenma wrote: ↑Sun Oct 23, 2022 7:51 pm I'm a little confused about what's needed for the dual ram. Obviously a second ram stick but something more as the Digital I/O board or that is not needed at all?

ntt wrote: ↑Sun Oct 23, 2022 9:29 pm The two SDRAM boards are meant to be installed directly on the DE10 nano connectors, you don't need an I/O board for that.
If you need an I/O board, only the digital one is shaped in a way to expose both the GPIO connectors of the DE10 nano (with an analog I/O board you can only fit 1 SDRAM).
If your have 1 SDRAM board, as it's usually the case, you can use either the analog or the digital I/O board - if you have any use for them, that is.

It isn't specifically the shape of the analog I/O board that prevents being able to use a second SDRAM module. It's using pins from the second slot for the analog video output. The digital IO board doesn't add any additional video output so it doesn't need any pins of the second slot. That's why the digital I/O board is the only one of the two options that lets you use the second SDRAM.

PhDTenma wrote: ↑Sun Oct 23, 2022 7:51 pm

Malor wrote: ↑Sun Oct 23, 2022 5:23 pm You wouldn't use it now, and it'll be easy enough to add later on, so I wouldn't personally buy a second stick yet.

I'm a little confused about what's needed for the dual ram. Obviously a second ram stick but something more as the Digital I/O board or that is not needed at all?

The MiSTer has two more or less identical GPIO connectors. A 'normal' board has one RAM stick inserted in one of the GPIOs, taking all the pins. If you buy a second, it goes into the other GPIO, also taking all the pins. At that point, you can only add a digital I/O board. The analog I/O needs some of the pins from the secondary GPIO port, so you can't do both dedicated analog and dual RAM.

You can still get analog output with dual RAM, however, by using a special mode on some of the HDMI pins. I haven't actually worked with this, but I got the impression that you can put a Y cable on it, and drive both digital and analog simultaneously. (or just analog, of course.) This is a relatively recent feature, sometime this year I think. Analog I/O was the first solution, while retasking HDMI pins is a newer, cheaper method, one that doesn't need any pins from the second GPIO.

But I haven't done that, and I am not certain it works that way, so if you're interested in the feature, get more knowledgeable people to tell you that it works the way you want it to. I know for sure you can get analog signals from the HDMI port. I am not certain that you can get both digital and analog simultaneously.

Don’t listen to the stupid FOMO. Dual ram will never make sense! Get that analog board, it rocks. If you’re not using a CRT with your mister, you might as well get a Raspberry pi or some other boring solution. Heck, just use your pc.

I know, but in this context a simpler answer was preferable IMO

DevilHunterWolf wrote: ↑Mon Oct 24, 2022 12:01 am It isn't specifically the shape of the analog I/O board that prevents being able to use a second SDRAM module. It's using pins from the second slot for the analog video output. The digital IO board doesn't add any additional video output so it doesn't need any pins of the second slot. That's why the digital I/O board is the only one of the two options that lets you use the second SDRAM.

ntt wrote: ↑Sun Oct 23, 2022 9:11 pm You only need double SDRAM boards for testing unfinished/unstable cores; some of them require dual SDRAM before they get optimized enough to run with just one - or even without it entirely
Basically all the devices a MiSTer is able to replicate - so far at least - only had a few megabytes of RAM, thus one SDRAM board should be all you need.

You are wrong about how and why Dual Ram works. Its nothing to do with the total ammount of memory. Its all to do with the bandwidth for memory transfers. With Daul ram you can effectively write and read from both banks near simultaneoudly and therefore have a much higher memory bandwidth.

If you dont need analogue output then get a digital board and then you will be ready for Dual Ram. Only buy an Analog IO board if you absolutely have to. You can still get a CRT signal from a digital IO board via an adaptor

(That came a bit harsh, don't you think?)
I do know all that, and my point stands: the memory latency is depending on how people write/optimizes the cores - or else you could just use the 1GB ARM RAM, if you could write the memory I/Os efficiently enough.
I don't think the original poster is interested in such a level of detail, though.

FPGA64 wrote: ↑Mon Oct 24, 2022 7:09 am You are wrong about how and why Dual Ram works. Its nothing to do with the total ammount of memory. Its all to do with the bandwidth for memory transfers. With Daul ram you can effectively write and read from both banks near simultaneoudly and therefore have a much higher memory bandwidth.

If you dont need analogue output then get a digital board and then you will be ready for Dual Ram. Only buy an Analog IO board if you absolutely have to. You can still get a CRT signal from a digital IO board via an adaptor

I didnt think it was harsh, sorry if you thought it was. The newer consoles have higher bandwidth requirementa. Sticking to single ram makes it harder to write and require heavy optimisation. The PSX core for example uses up valuable resources to allow it to work with single ram.

Jaguar for example has high memory bandwidth requirements. The saturn core currently works better with Dual Ram. Yes in the future it may be optimised to only need a single stick but I dont believe we should be restricted to single stick solutions.

Thank you all, guys!

I finally understood well the need of dual ram and why it was always mention in conjunction of digital I/O boards

FPGA64 wrote: ↑Mon Oct 24, 2022 7:09 am If you dont need analogue output then get a digital board and then you will be ready for Dual Ram. Only buy an Analog IO board if you absolutely have to. You can still get a CRT signal from a digital IO board via an adaptor

This is precisely what I was thinking. Unfortunately, I don't have space nor easy access to a CRT so I think I won't be using analogue output... So it's better to get a digital I/O and be prepared just in case the dual ram becomes a necessity or, If I see a good deal with a prebuilt MISTer with dual ram.

Thank you again!

ntt wrote: ↑Mon Oct 24, 2022 7:35 am I don't think the original poster is interested in such a level of detail, though.

but it was very instructive Indeed I was totally fine with the high-level answers and that's probably what all newcomers are looking for, but the details also makes this thread more useful for anyone interested in the need or not of dual ram.

To be honest I'm an avid user of the pre-alpha Saturn and Jaguar cores, as well as of the unstable dual-SDRAM PSX core, so I'm probably the last person who should discourage anyone from getting 2 SDRAM boards, but it's a niche user case I believe..

PhDTenma wrote: ↑Mon Oct 24, 2022 8:05 am Thank you all, guys!

I finally understood well the need of dual ram and why it was always mention in conjunction of digital I/O boards

FPGA64 wrote: ↑Mon Oct 24, 2022 7:09 am If you dont need analogue output then get a digital board and then you will be ready for Dual Ram. Only buy an Analog IO board if you absolutely have to. You can still get a CRT signal from a digital IO board via an adaptor

This is precisely what I was thinking. Unfortunately, I don't have space nor easy access to a CRT so I think I won't be using analogue output... So it's better to get a digital I/O and be prepared just in case the dual ram becomes a necessity or, If I see a good deal with a prebuilt MISTer with dual ram.

Thank you again!

Unless you're trying to use a TOSlink aka S/PDIF connection to a receiver, you don't need the digital I/O board. You get perfectly good digital video and audio through the HDMI port, without needing anything extra.

The digital I/O gives you a TOSLink and some possibly useful buttons, but you can run perfectly well without it. The biggest reason I like mine is because it sends uninterrupted sound even when the monitor loses sync. For whatever weird reason, the monitor flicker as it resyncs feels much less intrusive when the sound is smooth. I notice this the most with the PS1 core, which changes resolution fairly frequently. The video flickers are tiny, but the HDMI sound takes longer to resume, and that just goes away with the separate TOSLink cable.

I'm glad I have mine, but unless you're in a similar situation, the I/O board won't add much to the base unit.

Malor wrote: ↑Tue Oct 25, 2022 3:37 am

PhDTenma wrote: ↑Mon Oct 24, 2022 8:05 am Thank you all, guys!

I finally understood well the need of dual ram and why it was always mention in conjunction of digital I/O boards

FPGA64 wrote: ↑Mon Oct 24, 2022 7:09 am If you dont need analogue output then get a digital board and then you will be ready for Dual Ram. Only buy an Analog IO board if you absolutely have to. You can still get a CRT signal from a digital IO board via an adaptor

This is precisely what I was thinking. Unfortunately, I don't have space nor easy access to a CRT so I think I won't be using analogue output... So it's better to get a digital I/O and be prepared just in case the dual ram becomes a necessity or, If I see a good deal with a prebuilt MISTer with dual ram.

Thank you again!

Unless you're trying to use a TOSlink aka S/PDIF connection to a receiver, you don't need the digital I/O board. You get perfectly good digital video and audio through the HDMI port, without needing anything extra.

The digital I/O gives you a TOSLink and some possibly useful buttons, but you can run perfectly well without it. The biggest reason I like mine is because it sends uninterrupted sound even when the monitor loses sync. For whatever weird reason, the monitor flicker as it resyncs feels much less intrusive when the sound is smooth. I notice this the most with the PS1 core, which changes resolution fairly frequently. The video flickers are tiny, but the HDMI sound takes longer to resume, and that just goes away with the separate TOSLink cable.

I'm glad I have mine, but unless you're in a similar situation, the I/O board won't add much to the base unit.

Don't forget the user port on the IO boards though, used for things like SNAC adapters and the mt32-pi. I do like the colored status LEDs on it as well. Then there's the SD card slot, but that is hardly ever used.

Oh, right, I forgot that! I'm even using mine for the MT32-Pi, and totally forgot about it. User port is definitely a good thing.

I'm not hugely fond of the extra LEDs on the digital I/O. Their constant flashing is a little annoying.

Thank you both, I wanted an I/O Board also because of the buttons: if you have a problem with the keyboard at least you can get the menu and load cores, without that I think is not possible, right? Also, the user port, yes

Another thing is that when you buy pre-builds the usually include an I/O Board and even the standard kits include it. At the moment, I'm ambivalent between buying a prebuild unit or buying on my own the DE10-Nano and then the parts, but that's another topic

PhDTenma wrote: ↑Tue Oct 25, 2022 12:31 pm Thank you both, I wanted an I/O Board also because of the buttons: if you have a problem with the keyboard at least you can get the menu and load cores, without that I think is not possible, right? Also, the user port, yes
...

You can always use a controller to get into the menu, load cores, ...

jca wrote: ↑Tue Oct 25, 2022 1:06 pm

PhDTenma wrote: ↑Tue Oct 25, 2022 12:31 pm Thank you both, I wanted an I/O Board also because of the buttons: if you have a problem with the keyboard at least you can get the menu and load cores, without that I think is not possible, right? Also, the user port, yes
...

You can always use a controller to get into the menu, load cores, ...

Well, yes but only if you have a controller with enough buttons, right? In my brief time with a MISTer I had problems with controllers so maybe was because of that.

One button to activate the menu, the D-pad to navigate, one button for OK covers most of everything. You can also setup one button or a combination of 2 buttons to unmount disks, I am not sure as I always use BS on the keyboard.