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Made ROM SIMMs, wrote ROMdisk driver, need help debugging


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8 hours ago, JDW said:

Thank you for the EBAY link.  They look very nice.  I love the metal tabs.  Sadly, they are not the type for the SE/30 though:

 

EBAY RAM SIMM Sockets:

image.thumb.png.21c5a5087df3ddb8cf8e43689037454f.png

 

SE/30 RAM SIMM Sockets (spaced apart) as shown on my motherboard:

 

image.thumb.png.c653df65a9882d1912cfc10ef6c16406.png

I have angled metal tabbed 30pin 2 row ones.  I wonder if it would be possible to use those.  It is the same as used on the regular SE.  I'm thinking if anything it could be too tight on one side. 

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9 hours ago, maceffects said:

I have angled metal tabbed 30pin 2 row ones.  I wonder if it would be possible to use those.  It is the same as used on the regular SE.  I'm thinking if anything it could be too tight on one side. 

The angled RAM SIMM sockets used on a Macintosh SE motherboard also have a gap as shown here:

 

image.thumb.png.d576996142ab8c52026b9879d4d1fbb8.png

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@JDW Good catch. I didn't think they would have different pitches. The pitch for the SE/30 looks to be 0.4" (~10mm). It may be difficult to find an exact replacement, so I think single sockets would be a good, easier to find alternative. Another advantage is if you want to fix just one broken socket, then you could clip the supports in between the two sockets and leave the other one alone.

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One option could be manufacturing adapter boards that mate with the SE/30 (or other model) motherboard via solder tabs, also some later era LC/Quadra/Centris models with the ROM socket solder holes unpopulated and either have the ROM board directly on that, or have that board have a new ROM SIMM slots. The slot, socket, port and other connector manufacturers even when initially out of stock, will re-run batches on demand, if the batch order count is high enough. In some cases "just" 1000 pieces, which could be doable in some group funding thing.

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8 hours ago, tt said:

@JDW...I think single sockets would be a good, easier to find alternative. Another advantage is if you want to fix just one broken socket, then you could clip the supports in between the two sockets and leave the other one alone.

True, but it could be that Apple deliberately choose dual sockets to ensure the user wouldn't apply too much pressure and break the solder joins on the pins.  With a single socket, all the force will be applied to its pins only.  With the dual sockets, that force is spread across two socket's worth of pins.

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Since 72 pin SIMMs are more affordable in higher capacities and they're electrically compatible with the 30 pin SIMMs. Each group of four 30 pin SIMMs map to a single 72 pin one. So how about some board-to-board adapter with two angled 72pin SIMMs to replace the eight 30 pin ones? Or even better, some modern-ish soldered on 128MB memory module that solders into the holes left by the 30 pin SIMMs?

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That's an interesting idea. I guess if it was cheaper than 30pin SIMMs and looked cool some people might go for it. If it could do more than replace the RAM then it would get even more interesting.

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But what i'd really want is some redesigned full motherboard replacement good old chips from corroded boards could go into and have some modernization for these memory modules (or just soldered-on maximum capacity RAM). Saved space would provide enough space for integrated upgrades, such as maybe some integrated CPU accelerator and graphics card too (let's say sacrificing external floppy port for a video out connector). Lots of reverse-engineering though, and would more or less require some SE/30 core logic thing. At that stage, also adding soft-power would be pretty cool too, if replacing the PSU by some small ATX-like thing.

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11 hours ago, tt said:

@JDW Good catch. I didn't think they would have different pitches. The pitch for the SE/30 looks to be 0.4" (~10mm). It may be difficult to find an exact replacement, so I think single sockets would be a good, easier to find alternative. Another advantage is if you want to fix just one broken socket, then you could clip the supports in between the two sockets and leave the other one alone.

I bought a bunch of dual vertical 30 pin sockets from, IIRC, Jameco when they were closing them out.  They are also spaced too close together, but they are relatively easy to cut apart and use individually.  I use a small bench vise to hold them and a cutting wheel on a dremel to do the cutting.

 

While a dual socket might provide some superior lateral stability, the cut-apart individual sockets do still have the strain relieving plastic pegs.

Edited by trag
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9 hours ago, trag said:

30 pin sockets either straight or angled available here:   https://www.peconnectors.com/sockets-pga-cpu-and-memory/

Thank you for the link!

 

I still feel that the stock dual sockets will offer more resilience against solder joint cracking and offer less strain on the socket  legs over time than a single socket, especially if you swap RAM often.  But it seems the dual socket kind are no where to be found.

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We're getting a bit far afield here. SIMM socket replacement has been a recurring theme in many topics, now's probably a good time for someone to get a dedicated thread going in Hacks.

 

On 9/21/2020 at 4:49 PM, jammi said:

Since 72 pin SIMMs are more affordable in higher capacities and they're electrically compatible with the 30 pin SIMMs. Each group of four 30 pin SIMMs map to a single 72 pin one. So how about some board-to-board adapter with two angled 72pin SIMMs to replace the eight 30 pin ones? Or even better, some modern-ish soldered on 128MB memory module that solders into the holes left by the 30 pin SIMMs? 

We've been kicking the 72-pin SIMM and modern memory on the board notions around in Macintosh SE/30 Schematics (modernization effort)

 

As a teaser, you can see height's no problem if using angled sockets. Working on a refit board for my SE/30's busted socket bank: 72-pin SIMM injection for updated SE/30 Schematic?

 

SIMMs-under-Plexiglass-2.JPG

 

Now if I could just develop adequate desoldering skills. ::)

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9 hours ago, Trash80toHP_Mini said:

We've been kicking the 72-pin SIMM and modern memory on the board notions around in Macintosh SE/30 Schematics (modernization effort)

 

As a teaser, you can see height's no problem if using angled sockets. Working on a refit board for my SE/30's busted socket bank: 72-pin SIMM injection for updated SE/30 Schematic?

 

Now if I could just develop adequate desoldering skills. ::)

Thanks, that looks awesome! I've found things with heavy ground planes such as the SIMM slots on SE/30 are easier to desolder with a SMD rework station's hot air blower than desoldering gun.
I've used the desoldering gun on the through-holes after I've picked the socket off to clear the holes from old solder.

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Please let me know your thoughts on these AMP 822113-2 dual-sockets (30-pin). 

 

For the life of me, I cannot find the AMP drawings or schematics. The Length is probably right, but the Width is wider than the stock sockets, or at least it would seem when looking at the EBAY listing photos.  If you look at my SE/30 motherboard RAM sockets, you will see they are a perfect rectangle. But the EBAY sockets have little parts at either end which jet out a bit.  Even so, there is a gap between each dual socket on the motherboard.  I just cannot tell from the EBAY photo of the two parts that jet out would be longer than that gap. Can you?

 

Normal SE/30 motherboard SIMM sockets:

image.thumb.png.703bbf74f3e5529d89f5b9285b4c0e82.png

 

AMP 822113-2 dual 30-pin SIMM sockets:

image.png.4ed2059731a2183baa8196ef091f1311.png

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This is becoming widely far afield, I think we really need to spin this memory socket tangent off into a dedicated hacks topic @Cory5412

 

https://www.te.com/usa-en/product-822113-2.html

Customer drawing spec is .5" (1/2") spacing vs. what looks like .375" (3/8") spacing for the upright paired sockets on my SE/30 board.

https://www.te.com/commerce/DocumentDelivery/DDEController?Action=showdoc&DocId=Customer+Drawing822113JtifEnglishC_822113_J.tif822113-2

 

Single SIMM sockets are the way to go it seems.

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  • 2 weeks later...

The last we heard from @ZaneKaminski in this thread was August 9th.  It's Oct. 13th today.  I can understand being very busy for a few weeks, but it's been more than 2 months.  I can't help but worry about what might have happened.  Zane, if you are listening, despite your busy schedule, please check in by posting a single sentence saying, "Guys, I'm still alive!"  Thanks!

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I guess I'll contribute to this tangent, too. :)

 

It looks like PE connectors also sell dual 30 pin sockets. The product they offer looks similar to the eBay product that @JDW was discussing previously. Thankfully, PE Connectors provides technical drawings of the sockets, so one could determine if they will fit or not.

 

https://www.peconnectors.com/sockets-pga-cpu-and-memory/hws9229/

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  • 2 weeks later...

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