Macintosh SE/30 logicboard recreation (thread revival)

[craig1410]

Indeed, could we but get together in the real world to share those beers, efforts and yarns.

A great idea! Let's hope that as 2022 progresses, this sort of meet up becomes more a more likely to happen!

 

[NECyclone]

Thanks for the replies guys. I got into this wondering if $500 was in the ballpark. I did not realize how much time you guys were putting into this to make it work. It certainly is a "labor of love" for you guys and it becoming simply a "labor" is not likely going to happen nor should it. Just keep doing what you guys do though, it's fantastic.

 

[craig1410]

Hi,
Final update on the 25 pin D and PDS connectors.

I received my mouser order today with the correct footprint 25 pin D connectors and the solder pin PDS connectors and I have updated my mouser basket with these items. They are both now fitted to my board and look great! The 25 pin D connector has a hexagonal post rather than a circular one but that is the only aesthetic issue. The footprint is correct and the flange sits nicely against the board edge just like an original connector. The PDS connector is also correct and has solder pins this time instead of press-fit pins. It just dropped into position and is now fully soldered as well.

I'm doing a bit of testing of the board now but assuming everything works as expected I will take the board back out and give it a proper cleanup and take some final photos. I've also got 128MB of RAM on its way from Keystron which I'll install just for fun but I'm planning to split it between this board and my other SE/30 board. 128MB is cool "because you can" but I think 64MB is plenty.

I also got a BlueSCSI kit which is assembled and ready to test out. Looking forward to seeing how it compares to the SCSI2SD v5.2 I already have.

Any questions - please ask!

 

[Scott Squires]

I've also got 128MB of RAM on its way from Keystron

FYI, the 16 MB 30-pin SIMM modules by Keystron on eBay use 2x MT4LC16M4T8 chips (16Mx4) per SIMM. These are 3.3v parts, specified for operation at supply voltage up to 3.6v. They're made for 3.3v 72-pin SIMMs, never 30-pin SIMMs (which are always operated at 5v). I suppose Keystron might test these and bin them for ones that work at 5v, but it all seems quite sketchy to me. There's a reason they cover the chip markings with a "warranty void" sticker.

 

[craig1410]

FYI, the 128 MB 30-pin SIMM kit by Keystron on eBay uses 2x MT4LC16M4T8 chips (16Mx4) per SIMM. These are 3.3v parts, specified for operation at supply voltage up to 3.6v. They're made for 3.3v 72-pin SIMMs, never 30-pin SIMMs (which are always operated at 5v). I suppose Keystron might test these and bin them for ones that work at 5v, but it all seems quite sketchy to me. There's a reason they cover the chip markings with a "warranty void" sticker.

Hi, that's interesting.

I actually got the recommendation to use Keystron or Memory Masters by @ZaneKaminski after I inquired with him about buying some RAM from Garrett's Workshop. Unfortunately GW doesn't have any stock just now and it's probably going to be a little while before they do another production run. It's two 64MB (16MB x 4) kits that I've ordered and they are listed as being compatible with the SE/30 amongst others. How confident are you about your information?

 

[Scott Squires]

100% confident. I'm looking at them right now. I edited my post while you replied. It was the 64MB kit that I purchased. But it does look like all their 16 MB modules are the same design.

 

[Scott Squires]

There are people here who are using Keystron 16 MB modules and it works. But it *is* overvolted.

 

[cheesestraws]

Memory Masters

The ones I've had from Memory Masters do use proper 5V chips, as far as I can see.

 

[craig1410]

Oh well, it's too late to cancel the order now.
I could have gone with Memory Masters or Keystron but IIRC Memory Masters were charging twice as much for delivery and had a slightly poorer feedback rating than Keystron.

Thinking about the issue of running over voltage, I wonder just how much of an issue that is likely to be, especially since the SE/30 is running at a much slower access speed (120ns) than the 60ns rating of these modules. That might help to reduce any excess heat that might otherwise build up.

Anyway, I appreciate the heads-up. I'll see if they work when they arrive and if not then I'll certainly challenge Keystron about it. If they do work then as long as they don't get any hotter than other SIMMs then I'm not too concerned.

Edit: I've sent a message via eBay to the seller so we'll see what they say.

 

[craig1410]

I've had a reply from Keystron already and although I don't want to directly quote the guy since I don't have permission, I can paraphrase a few points:

1. He doesn't deny that they are using 3.3V chips
2. He says they tested these 3.3V chips from various manufacturers many years ago and found that they would work reliably at 5V without any overheating issues.
3. He says their product has many years of trouble free operation.
4. Keystron will stand behind their product with a lifetime warranty and they encourage anyone who is having problems to contact them for support.
5. He has heard it said that 3.3V and 5V parts are made using the same process but the batches with faster chip speeds are labelled as 3.3V parts. He concedes that this statement has questionable credibility although it sounds plausible at least.

So I think that's a pretty good response to a valid concern and I look forward to receiving my SIMMs. I hope this is helpful to others looking to buy RAM.

 

[Scott Squires]

On one hand, it sounds somewhat reasonable, considering sourcing issues for obsolete chips. On the other hand, it irks me that they hide the fact that they are operating out-of-spec. Also if they truly stand behind their hardware, they should discontinue their use of these "warranty void" stickers.

 

[craig1410]

On one hand, it sounds somewhat reasonable, considering sourcing issues for obsolete chips. On the other hand, it irks me that they hide the fact that they are operating out-of-spec. Also if they truly stand behind their hardware, they should discontinue their use of these "warranty void" stickers.

It seems to me that they are applying a "common sense" approach to provide a product that is in demand but which otherwise would have cost driven up and/or supply restricted due to the lack of suitable 5V DRAM chips. I wouldn't expect them to advertise the fact that they are using 3.3V parts but they certainly didn't try to lie about it when I challenged them. It's not as if we're running these machines in a data centre or as part of some mission critical system. If we were then we'd be looking for ECC modules instead and we'd certainly not be expecting to see 3.3V parts running at 5V in that instance.

They are taking the risk of these modules failing by providing the lifetime warranty but presumably their experience is that they very rarely DO fail otherwise this wouldn't be a viable solution. The warranty stickers are pretty common practice and, even though they carry very little legal importance from what I've read, the only reason anyone would really have for removing it in this case is to see what chips they are using, perhaps with a view to reverse engineering the module. It's not like it's a warranty seal sticker preventing you from opening up a games console or something.

Anyway, getting back on topic, I'll be sure to provide a quick update once I've tried them out and will post a photo of my completed board with obligatory 128MB of RAM installed.

 

[superjer2000]

I’ve had good luck with other world computing‘s 16mb kit and it seems cheaper too. I just ordered 8 more 16 mb simms.

 

[craig1410]

I’ve had good luck with other world computing‘s 16mb kit and it seems cheaper too. I just ordered 8 more 16 mb simms.

Yeah and it looks like they also ship to the UK. Total price for 8x16MB SIMMs shipped to the UK is $103.58 compared to $137.72 for Keystron. That's a decent saving.

I can't quite make out the chip part number but there are certainly 8 of them instead of 2 with the Keystron module. I wonder if these are 3.3V or 5V. And just look at that "Warranty Void If Removed" sticker.

 

[craig1410]

@Bolle and anyone who is building or about to order PCBs for SE/30 Reloaded, I think there is a very minor PCB error which affects the printer port. On the schematic (original and remastered) the following traces are specified:

RP3 pin 13 to UD12 pin 14
RP3 pin 14 to UD12 pin 13

However, on the Rev 02 PCB these are reversed. This effectively inverts the TXDB+ and TXDB- signals for the printer port which is probably why I can't get that port to pass tests in Snooper. The modem port passes tests fine so presumably it's okay.

I've not reworked the board yet as I can't quite bring myself to install bodge wires yet but just wanted to give folks a heads up in case anyone was just about to order some boards. Might be worth waiting for a fix if Bolle has some time. I don't think it'll be a hard one to fix hopefully, and the rework on existing boards should be minimal. I'll post a photo once I've done it and confirmed it fixes the printer port issue.

 

[Bolle]

RP3 pin 13 to UD12 pin 14
RP3 pin 14 to UD12 pin 13

Ha, good one. Fixed and updated board files.
Easiest to rework that will probably be to cut the traces that come out of RP3 at pins 7 and 8 and wire them right to the port.

 

[craig1410]

Ha, good one. Fixed and updated board files.
Easiest to rework that will probably be to cut the traces that come out of RP3 at pins 7 and 8 and wire them right to the port.

Wow, 25 minute response time - not bad!

Happy to confirm I've reversed my lines and Snooper now reports no problems at all! Happy days!

Seems an appropriate time to post photos of my finished board both with and without the socketed chips and also showing my printer port rework and clean Snooper tests.

Thanks again to Bolle and everyone else who has contributed to this amazing project. Now I just need to figure out what to do with my working SE/30! Dark Castle seems like a good place to start!

 

[PacificState]

Perfect - Bolle, does this have the tweaked SIMM holes?

 

[PacificState]

(also - I *really* *really* appreciate you doing this in the first place, and keeping it updated!)

 

[Bolle]

Perfect - Bolle, does this have the tweaked SIMM holes?

Yes.