CPS3 NOR Open SIMMs

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BigP_BigP

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I am not sure if anyone here is interested in this type of project, but I was for a few reasons (mainly to get my own CPS3 working with all 6 titles). While looking into them I made a few interesting discoveries that are not widely publicised and may assist anyone looking at taking on this project. This is based on early testing so ill update it when or as I know more.
1. They appear to be 100% compatible with the UltraBios, so you dont need to update your cart again if you already have an UltraBios.
2. The instability issues mentioned on the github appear to stem from the LS148a. This part appears to be to slow to turn off (tDIS) causing the mentioned instability. It can be fixed by using a 74F148 in the same location. I suspect a 74LVC148 would also achieve the same thing but have not tested it. This is important because the 74F is obsolete and difficult to obtain where as the 74LVC is still in production.
 
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pubjoe said:
If you're looking to make batches I'm interested in buying a set.
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I was not planning on it and that was not the intention of this post. There are a few reasons for this, but things could change if there was enough interest.

Having said that because you have to order PCBs in lots of 5 I have 2 (and a half) sets (5 64mb simms and 10 128mb) on hand. If your interested in 1 remaining full set i could work something out with you (i was planning on putting the extra set up on my eBay store at some point anyway).
 
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yoganuggy said:
There was a thread on arcade projects about this. The commercial simms are made by darksoft and he feels the open simms are a clone of his work so you can't talk about them there.

Example of closed thread

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Yeah its tricky and i dont really know all the history on that. What i can say from building a set is that they are slightly different but if you made the chang to VLC i suggested above they would start to look very similar indeed. Darksoft is very kind with sharing his work whenever I have asked. I dont really want to annoy him. I personally thought it a little rude to post about a compering product on a forum he uses to distribute his products and had a big part in getting up and running. A bit like sticking an ad for a local hamburger shop up in McDonalds window... probably wouldn't go down well.
I felt this info could help anyone thinking about trying to build some and would be good to have out there but didn't really think it was an option to post it on AP.
Its also why I have been a little reluctant to build a large batch. However with the price of NOR flash I suspect that prices of the commercial option will rise significantly and/or may even become difficult to find. So it would be nice to have both a replacement SIMMs and multigame solution available without totally breaking the bank. After all there are only 6 games and 3 or them are SF3.
 
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OK I have these fully working. There are a few more things that anyone attempting to build these should know.

1. As mentioned before you need to use 74F148 in the place of 74LS148. I suspect 74LVC148 will also work but it have not tested it.
2. You need to use Micron flash for BOTH 128mb and 64mb SIMMs. This use for a few reasons that will become apparent in a second.
3. I recommend that you use them with UltraBios NOT the NOS bios. This is because when you dig into the NOS bios there are a few issues. This creates some rather large ethical issues for me as the SIMM hardware is not too hard to replicate, however the Bios mod would have taken considerable work. This is the largest reason I am not willing to sell these unless there is no other option available. Using the NOS with UltraBios is only possible if you use Micron flash for both SIMM sizes.
4. I had rather large issues with pin contact on 1 of my SIMMs. This was a tolerance issue. When I measured all of the SIMM thicknesses most were very close to 1.2mm but the one giving me issues was closer to 1.1mm (1.08mm). To find and fix this I had to buzz out every pin in the slot to its contact pad on the SIMM. I would not have worked this out for ages if it was not foe @cruzlink32 on AP (thanks). Then I had to bend the pins that were not making contact ever so slightly. As well as this I had to reseat a few headers on the game selector board so it was not pulling any pressure on the SIMMs, in turn pulling them away from the pins.

Hope this helps anyone trying these. I decided to build these for 2 reasons.

The first to see how much of a rip off of Ultrasimms they really are. The hardware is very similar and the BIOS supplied with the NOS has some issues so I will leave that up to you to make your own decision about.

It is possible that at some point in the future the issues with the NOS bios will be sorted but for now they are slightly problematic.

The second was to learn a bit more about the CPS3 hardware and that I did.
 
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BOM cost was about $250aud (£135). With the research and finding the right parts to fix the instability issues about 12-14 hrs but with the info provided if you are competent st SMD soldering you should be able to get that down to 4-5 hrs actual work. If you are not well versed in SMD I would say its still possible but maybe double that to account for learning a bit.
 
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