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Made ROM SIMMs, wrote ROMdisk driver, need help debugging
Posted by: JDW on 2020-09-21 08:08:05 I haven't replaced the RAM sockets yet, but I did recently buy some from an eBay seller that come in a lot of 10 pcs. RAM sockets with METAL tabs, by chance?
Posted by: tt on 2020-09-21 08:29:24 Yes... QTY (10) 30 POSITION DUAL SIMM SOCKETS SMV2030-6 AUTOTEK
Posted by: JDW on 2020-09-21 08:58:02 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: SE/30 RAM SIMM Sockets (spaced apart) as shown on my motherboard:
Posted by: maceffects on 2020-09-21 09:19:35 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: View attachment 37451 SE/30 RAM SIMM Sockets (spaced apart) as shown on my motherboard: View attachment 37452 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.
Posted by: JDW on 2020-09-21 10:24:16 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:
Posted by: maceffects on 2020-09-21 10:25:35 @JDW if the space is the same it should fit, I just hope it will clear the ICs. I may try because I have a few boards with broken plastic clips.
Posted by: tt on 2020-09-21 12:46:41 @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.
Posted by: jammi on 2020-09-21 12:51:26 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.
Posted by: JDW on 2020-09-21 13:11:14 @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.
Posted by: Trash80toHP_Mini on 2020-09-21 13:37:57 Nap, it's just half the time stuffing the board using paired sockets and pairs sit more flatly/steadily than singletons with the wider baseline for the wave soldering process. [😉]
Posted by: tt on 2020-09-21 13:46:53 Agreed, mechanically it doesn't buy much, it's more for production. The 68 pin socket is on its own and many other designs are single sockets as well.
Posted by: jammi on 2020-09-21 13:49:59 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?
Posted by: tt on 2020-09-21 14:43:25 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.
Posted by: jammi on 2020-09-21 14:46:28 I guess one thing such a module could do would be battery-backed RAM for read-write RAM disks and such, and could incorporate the ROM-SIMM functionality too, since they're on the same address and data paths afaik.
Posted by: jammi on 2020-09-21 14:53:02 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.
Posted by: trag on 2020-09-21 16:11:49 RAM sockets with METAL tabs, by chance? 30 pin sockets either straight or angled available here: https://www.peconnectors.com/sockets-pga-cpu-and-memory/
Posted by: trag on 2020-09-21 16:15:10 @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.
Posted by: JDW on 2020-09-21 17:11:39 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.
Posted by: Trash80toHP_Mini on 2020-09-26 23:56:05 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. 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? View attachment 35317 Now if I could just develop adequate desoldering skills. :🙂
Posted by: jammi on 2020-09-27 01:03:29 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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