SDRAM board

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tomywong
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Re: SDRAM board

Postby tomywong » Thu Jan 24, 2019 11:26 am

I want to make sdram card for myself. Can someone tell me what is the thickness of sdram card PCB ? Thank you.

THaase
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Re: SDRAM board

Postby THaase » Thu Jan 24, 2019 12:27 pm

'Normal' 1.6mm

tomywong
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Re: SDRAM board

Postby tomywong » Thu Jan 24, 2019 2:27 pm

Thank you THaase :D

hyiger
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Re: SDRAM board

Postby hyiger » Sun Mar 17, 2019 6:02 pm

I'm a bit late to game in this forum, just started with the MiSTer project but some notes with regard to soldering the SDRAM board. I've done a lot of soldering over the years. I also have a reflow over, hot air station and of course a hand iron. I've built 5 RAM boards (for myself and friends) and consistently get 160+ with Alliance RAM.

1. First I suggest using Alliance memory, getting cheap or NOS memory on eBay will most likely end if grief. Don't panic about not achieving 160+mHz in a memory test, 150mhz is sufficient. I suspect 99%+ of the cores can't go that high anyway. A typical fMax on DE10-Nano boards with the T80 core (used for most of the arcade cores that require a Z80) is probably around 150-155 and that's on a good day... Probably more like 130-135mhz is to be expected. In other words if you can pass at least a 150mhz test then you are fine. In fact you are probably OK with on 140mhz.

2. Any SMD 0805 package capacitor in the range of 0.1uf - 1.0uf will work. That is, you don't need to get the "exact" Kemet part.

3. No need to go overboard and use a stencil with solder paste and a reflow oven (unless you have one of course). However, I suspect if you have a reflow oven you don't need my advice :) . The chip can easily be hand soldered even if you are new to soldering.

4. I suggest soldering the RAM using a "drag solder" technique and plenty of liquid flux (there are probably plenty of Youtube videos on this). There is no need to solder pin by pin, besides it will take forever. Drag soldering takes seconds. For SMD hand soldering, I use Kester 959T Soldering Flux and Kester 32117 Solder (1.57mm) with a small chisel tip. I've tried many types of solder over the years and I've found that Kester is the best. Secure opposite corners of the ram with solder, apply lots of flux to the pins (but don't go overboard), apply solder to a clean tip then drag it across the pins. Repeat 1 or 2 times as needed. Apply a little bit more flux to clean up any bridges with iron. Should take only a couple of passes and it's quick and effective. Inspect with a 10x loupe or microscope. Note: High quality solder and flux is a must! Do not use cheap solder! If soldering by hand I suggest using 60/40 tin/lead solder (unless you are environmentally conscience, but lead-free soldering can be tricky)

5. Remove flux and debris afterward. Although there are differing views on this, RAM can be sensitive to stray capacitance and certain fluxes can cause problems in this area (I find I get better performance after cleaning the board). Note: you do not need to buy specific "Flux Remover". I use Isopropyl alcohol (ethanol or methanol work fine as well) in a high concentration (around 90%) and a soft-bristle toothbrush. This can be purchased easily in a pharmacy (chemist). I usually rinse the board immediately afterward with demineralized, distilled water but this is probably not necessary. Do not rinse the board with tap water!

5. Again, inspect the solder around the pins using 5-10x magnification to look for: not enough solder, too much solder and most importantly solder bridges. Also make sure there are no debris around the pins (especially fine copper wire if you used a solder braid to clean up excess solder).

uigiflip
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Re: SDRAM board

Postby uigiflip » Thu Jul 11, 2019 3:14 pm

I know some people are now testing 64MB sdram, is it true there could be possibility of plugging in a second 64MB sdram on unused pins for more memory for neogeo core (and possibly others core maybe minimig)?
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Sorgelig
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Re: SDRAM board

Postby Sorgelig » Thu Jul 11, 2019 3:53 pm

uigiflip wrote:I know some people are now testing 64MB sdram, is it true there could be possibility of plugging in a second 64MB sdram on unused pins for more memory for neogeo core (and possibly others core maybe minimig)?

There will be an option later.
Cannot tell any specific details as it's still in development.

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Re: SDRAM board

Postby PhantombrainM » Mon Jul 22, 2019 8:14 pm

By the way...if we have ~700mbit with 64MB SDRAM Module for NeoGeo and the biggest games have 706mbits...
...can't we just copy the sound ROM's to DDR3?
I think this will free up the left 6mbit's and I don't think that soundfiles/music needs high data throughput?
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THaase
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Re: SDRAM board

Postby THaase » Tue Jul 23, 2019 4:28 am

It will be either 32MB (256MBit) OR 64MB (512MBit) - not both together. (How do you count ~700?)
1GBit Chips are only available as BGA - this will cause (at least) new board, 4Layer and big soldering problems for normal people.
And I'm also not sure (have not count) it we would have enought address lines at all (possible).

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Re: SDRAM board

Postby quack75 » Tue Jul 23, 2019 5:16 am

MiSTer now supports 128MB dual SDRAM ?

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Re: SDRAM board

Postby THaase » Tue Jul 23, 2019 5:36 am

No - why do you think so?
At the moment Sorgelig is thinking about exchanging the 256MBit SDRam chip with a 512MBit one with the same footprint afaik.

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Re: SDRAM board

Postby quack75 » Tue Jul 23, 2019 8:09 am

THaase wrote:No - why do you think so?
At the moment Sorgelig is thinking about exchanging the 256MBit SDRam chip with a 512MBit one with the same footprint afaik.


Cause SmokeMonster said so and he is generally well informed:
https://twitter.com/SmokeMonsterTWI/sta ... 4714981376

MiSTer now supports 128MB dual SDRAM and Sorge has been heavily editing @furrtek
's Neo Geo core. Although this doesn't necessarily mean that 128MB will be required--options are still being explored.

THaase
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Re: SDRAM board

Postby THaase » Tue Jul 23, 2019 9:17 am

Yes - you're right - I can also see it in the commits from Sorgelig .... well let's wait :D

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Re: SDRAM board

Postby NobleX13 » Mon Aug 05, 2019 3:40 pm

I just wanted to drop in and say that I built my first SDRAM boards today. Getting just the right amount of solder on the connector pads can be finicky, but after some practice it is pretty easy. I used some MG Chemicals solder paste for the actual memory module and the capacitors. Worked a treat!

I also quickly learned to use the DE10-nano to determine the spacing for the three-pin header. I had to desolder my first one and spend some time cleaning out the vias to get it fixed.

Both of the modules I have assembled so far have passed the memory test core at 167 MHz. Pretty pleased with this so far.

I have another eight boards to build. This project was the boost I needed to get into SMD soldering seriously and I cannot thank you enough. Obviously I only need one board for my setup, but I figured I would build all ten as practice.

I also went a little crazy and ordered parts for a batch of IO and USB boards.

Here is a completed pic. Please ignore the flux residue; the black solder mask makes it look worse than it is.

Image
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