SDRAM board

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SDRAM board

Postby Sorgelig » Sat Sep 02, 2017 5:46 pm

This thread is about SDRAM board only.

Post your questions and suggestions here.

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Re: SDRAM board thread

Postby Sorgelig » Wed Sep 06, 2017 6:58 pm

SDRAM_rev board will become obsolete and incompatible when 4.0+ I/O board will be released.

The main SDRAM board design is SDRAM_uni v3.1U or older SDRAM v3.1.

Horizontal inward direction won't be supported if you will need new I/O board.

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Re: SDRAM board thread

Postby jcw » Sun Oct 15, 2017 9:20 pm

I'm just starting out on MISTer. Have assembled an V3.1R board today (horiz-inwards IIUC).

Is there any public information about your plans for the future V4 io-board at this stage?
I'm not asking for a timeline, just trying to gauge in what direction things will be g(r)o(w)ing...

(with a big thanks for all sharing all your efforts!)

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Re: SDRAM board thread

Postby Sorgelig » Sun Oct 15, 2017 10:43 pm

Latest I/O Board is v5.2. Newer version of I/O board includes features of older versions. So there is no plans to develop v4.x anymore as it's superseded by v5.x

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Re: SDRAM board thread

Postby jcw » Sun Oct 15, 2017 10:57 pm

Ah, of course - I've been reading up on the other threads. Ok, all clear now.

And the SDRAM board is working perfectly here at 140 MHz.
Thanks also to the excellent beginner's guide on the GitHub wiki.
Enough for some beginning MiSTer core explorations. Great!

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Re: SDRAM board thread

Postby TorsteinP » Mon Oct 16, 2017 7:25 am

jcw wrote:I'm just starting out on MISTer. Have assembled an V3.1R board today (horiz-inwards IIUC).

Is there any public information about your plans for the future V4 io-board at this stage?
I'm not asking for a timeline, just trying to gauge in what direction things will be g(r)o(w)ing...

(with a big thanks for all sharing all your efforts!)

Just a quick note: Inward SDRAM wount work with new I/O board 5.2. It covers the area used by SDRAM board.

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Re: SDRAM board thread

Postby jcw » Mon Oct 16, 2017 9:02 am

Yes, found out after I had placed the order at OSH-park. No prob.
Plenty to try out - I'll probably hand-wire an SD card to try the other cores.
Thanks for the heads up.

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Re: SDRAM board thread

Postby toromand » Fri Oct 27, 2017 5:41 pm

Strange thing. I have decided to try to salvage and resolder my faulty(the first one I have tried to make some time ago) that couldn't pass the high speed tests. After resoldering, it passes the 150MHz test (at least the 30min I have tried as I write this), but it does not work with the cores that use it.
Any thoughts?
My other board is working fine.

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Re: SDRAM board thread

Postby Sorgelig » Fri Oct 27, 2017 6:28 pm

I never encountered such problem. Have no idea...

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Re: SDRAM board

Postby Newsdee » Tue Dec 05, 2017 1:30 am

What are the P2 pins for?

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Re: SDRAM board

Postby Sorgelig » Tue Dec 05, 2017 3:40 am

Newsdee wrote:What are the P2 pins for?

it's for HW mod to wire to cold reset.
It's been discussed already in MiSTer generic thread.

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Re: SDRAM board

Postby Newsdee » Tue Dec 05, 2017 5:04 am

Sorgelig wrote:it's for HW mod to wire to cold reset.
It's been discussed already in MiSTer generic thread.

Found it:
viewtopic.php?f=117&t=31825&hilit=sdram&start=225#p323210

What about the other three holes? Is it P2R i.e. the same thing?
I suppose it means the board could be made with just three parts (capacitors, SDRAM and connector).

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Re: SDRAM board

Postby Sorgelig » Tue Dec 05, 2017 5:43 am

Newsdee wrote:
Sorgelig wrote:it's for HW mod to wire to cold reset.
It's been discussed already in MiSTer generic thread.

Found it:
viewtopic.php?f=117&t=31825&hilit=sdram&start=225#p323210

What about the other three holes? Is it P2R i.e. the same thing?
I suppose it means the board could be made with just three parts (capacitors, SDRAM and connector).


Oh, i didn't notice the thread is about SDRAM board. P2 and P2R are for Arduino header. Strange you're asking this.
P2R is for reverse mounting.

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Re: SDRAM board

Postby JimDrew » Tue Dec 05, 2017 7:33 am

If I wanted to make a SDRAM board with 128MB (32MB x 4), can you support it for the cores? This would require 4 extra pins on for the addressing. Could those be next to the 3 existing extra pins that plug into the Arduino header?
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Re: SDRAM board

Postby Sorgelig » Tue Dec 05, 2017 7:37 am

What's the purpose of 128MB of SDRAM? I don't see the cores requiring 128MB of SDR SDRAM.
And be sure the speed of this construction will be inferior. Something like 60MHz max.

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Re: SDRAM board

Postby JimDrew » Tue Dec 05, 2017 7:46 am

32MB is not enough memory for an Amiga core. My real Amigas have 64MB or more.

Why would the memory speed be restricted by increasing the amount memory (because of the new upper two address lines)?
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Re: SDRAM board

Postby Sorgelig » Tue Dec 05, 2017 9:34 am

JimDrew wrote:32MB is not enough memory for an Amiga core. My real Amigas have 64MB or more.

There is no reason to add more memory to Minimig in its current state. Minimig requires faster CPU and RTG to utilize more memory.
Even in current state on Minimig, it's possible to use DDR3 as FastRAM which can give you 256MB. But as i've wrote, i see no point of more memory without improve other parts.

JimDrew wrote:Why would the memory speed be restricted by increasing the amount memory (because of the new upper two address lines)?

GPIO used for SDRAM are not specialized for memory driving. It's OK to drive one chip, but not more. Even though only one chip of SDRAM is used now, it's very low powered. Check the specs of AS4 chip used on SDRAM board. It's lowest in power consumption among all other chips in this class. 60mA - only. Choose SDRAM chip with standard 120mA and the max speed you will achieve will be around 100MHz (or even 80MHz).

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Re: SDRAM board

Postby JimDrew » Tue Dec 05, 2017 3:52 pm

Sorgelig wrote:
JimDrew wrote:32MB is not enough memory for an Amiga core. My real Amigas have 64MB or more.

There is no reason to add more memory to Minimig in its current state. Minimig requires faster CPU and RTG to utilize more memory.
Even in current state on Minimig, it's possible to use DDR3 as FastRAM which can give you 256MB. But as i've wrote, i see no point of more memory without improve other parts.

JimDrew wrote:Why would the memory speed be restricted by increasing the amount memory (because of the new upper two address lines)?

GPIO used for SDRAM are not specialized for memory driving. It's OK to drive one chip, but not more. Even though only one chip of SDRAM is used now, it's very low powered. Check the specs of AS4 chip used on SDRAM board. It's lowest in power consumption among all other chips in this class. 60mA - only. Choose SDRAM chip with standard 120mA and the max speed you will achieve will be around 100MHz (or even 80MHz).


But only one SDRAM chip at a time would be driven, setup as 4 banks. There is plenty of power on the connector port.

32MB is really not enough memory for an Amiga. AmigaKit and such as selling 128MB and 256MB expansion boards for real Amigas. Whether the Amiga is 7MHz or 7GHz, memory is the number one requirement.
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Re: SDRAM board

Postby alexh » Tue Dec 05, 2017 4:49 pm

JimDrew wrote:32MB is really not enough memory for an Amiga.

I disagree. An 020 Amiga with no RTG does not really need any more. What AmigaOS program is going to use more than 32MiB? I can think of only 1 or 2.

JimDrew wrote:AmigaKit and such as selling 128MB and 256MB expansion boards for real Amigas.

You make it sound like people are regularly fitting 256MB in their A1200! These upgrades are for big box Amiga's. A3000/A4000 computers for those who have an accelerator with no DRAM controller (A3640) and too little money to buy a better accelerator.

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Re: SDRAM board

Postby JimDrew » Tue Dec 05, 2017 6:03 pm

The A1200 was a poor selling computer in the U.S. compared to the A2000, A3000, and A4000.

Ray tracing, desktop publishing, graphics design, hard drive backup, hard drive optimization, and a slew of other programs can use more than the 24MB FAST RAM limit of the current Minimig core (due to the available RAM). Of course, emulations can also use more memory as well. Even 48MB of extra RAM in Replay's Amiga core is not enough, which is why Mike added another 64MB on the daughterboard. The Vampire boards have 128MB of RAM. My real Amiga 3000 has 80MB of RAM. You can never have too much memory.

If drive power (I/O lines) is truly a concern then I can use bi-directional buffers and tri-state each SDRAM when not being accessed. People have asked me if I would make a memory board with at least 64MB on it, so I am asking if I design and build the boards could it be supported by MiSTer? Ideally I would like to have 128MB or 256MB.
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Re: SDRAM board

Postby alexh » Tue Dec 05, 2017 7:12 pm

JimDrew wrote:Ray tracing

Yes. Lightwave is perhaps the only program anyone would ever want to run on MiSTer which could use more than 24MiB

JimDrew wrote:desktop publishing, graphics design

MiSTer users are not really going to use these programs creatively on MiSTer when they can use a modern PC/MAC programs.

JimDrew wrote:hard drive backup, hard drive optimization

Both irrelevant to MiSTer users.

Minimig on MiSTer is far less useful than Replay as it has no 060 or RTG support. And Vampire is incomparable because it's increased CPU power means it can run modern programs with much higher memory overhead.

More RAM would be an interesting thing for the future if hybrid CPU emulation could be done

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Re: SDRAM board

Postby Sorgelig » Tue Dec 05, 2017 11:34 pm

alexh wrote:More RAM would be an interesting thing for the future if hybrid CPU emulation could be done

And Hybrid emulation will use CPU+FastRAM on ARM side (DDR3), so SDRAM expansion is not required anyway.

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Re: SDRAM board

Postby ijor » Wed Dec 06, 2017 12:57 am

JimDrew wrote:If drive power (I/O lines) is truly a concern then I can use bi-directional buffers and tri-state each SDRAM when not being accessed. People have asked me if I would make a memory board with at least 64MB on it, so I am asking if I design and build the boards could it be supported by MiSTer? Ideally I would like to have 128MB or 256MB.


I"m not sure power is a problem. But certainly there is a problem of timing and signal integrity. This connector is not designed for high frequencies. We are quite lucky that the DRAM board works at these high frequencies. If you make the math and perform timing analysis the DRAM interface doesn't meet timing. It works mostly because the Alliance Memory part we use has some outstanding specs and probably performs even better than the specs. Probably also the FPGA specifications are a little too pessimistic.

Multiple chips will increase the risk of signal noise, delays and skew. But it is ultimately a matter of testing. Make a couple of boards and see what you get. Adding buffers might improve the signal integrity, but they will add some delay that might be critical. If you add buffers, choose fast ones.

Adding support at the core might be trivial assuming the Minimg core already supports extra DRAM with similar configurations on other platforms.

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Re: SDRAM board

Postby JimDrew » Wed Dec 06, 2017 12:59 am

The DE-10 is capable of running the Vampire core, with tons of room to spare. You are looking at what is available today for MIST (and MiSTer), not what people are actually working on in the FPGA world. Adding RTG to the Minmig is certainly possibly the Replay core is open source, and I know the guy that did the RTG driver. :)

You do know that I develop critical hardware for a living (UAV guidance and weapons control systems)? I have been designing hardware for 35 years now. I can certainly make a SDRAM board that is buffered correctly. I just need to know if I do it, you'll support it. I wonder if this would also help the performance of the 486 emulator using the SDRAM instead of on board DDR memory?
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Re: SDRAM board

Postby Sorgelig » Wed Dec 06, 2017 2:41 am

JimDrew wrote:Adding RTG to the Minmig is certainly possibly the Replay core is open source, and I know the guy that did the RTG driver. :)

Replay core is NOT open source. It will be open source when it will be available in public repository and license won't restrict to use it on other boards.
Give me the RTG source code and i will see if i will be able to integrate it.
I other thread Mike said that RTG on Replay is done on RPi module. If so, then it will be hard to port to Minimig.

JimDrew wrote:I can certainly make a SDRAM board that is buffered correctly.

You can use 64MB chip ISSI (version D - i forgot the part number, can check later if you need). It passes 130MHz memtest. It's backward compatible with 32MB chip and uses the same PCB. I've assembled one board with 64MB chip and use sometimes if more memory is needed. But this chip costs 4 times more than 32MB chip.
Currently Minimig supports only 32MB chip. I didn't check this part of Minimig and don't know how much effort it will require to add more memory. If there any restrictions or not.
Keep in mind, one of the main advantage of MiSTer is price. Making expensive extension boards which will be used only in single core is not reasonable.

JimDrew wrote: I wonder if this would also help the performance of the 486 emulator using the SDRAM instead of on board DDR memory?

nope. Original ao486 is running on DE1 board with SDR SDRAM and speed per-MHz is the same as on DE10-nano. The main problem is CPU model, not memory.


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