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I have a number of non-functional older PalmOS devices (of the 68000 processor variety, not the later ARM processor models). I'd like to be able to reuse the memory cards from these in new applications, but I'm struggling to find much information about the cards. What I can see is this:

  • The cards use a form factor similar to a modern SO-DIMM; the clip mechanism is essentially identical to a modern laptop's memory cards.

  • The interface has a 72-pin double sided connector.

  • Some of the devices I have have a seperate ribbon connector to the main board, although this may be a proprietory extension as these cards came from enhanced PalmV devices with barcode scanners manufactured by Symbol.

I would ideally like to know:

  • What precise connector model is used to hold these cards?

  • What RAM technology is used? (I'd usually assume traditional DRAM, but there's a possibility that SRAM was used to increase battery life)

  • What is the pinout of the connector?

  • What is the purpose of the extra ribbon cable connector on the Symbol devices?

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    IIRC the memory upgrades on those Palms were custom and could include other chips other than just memory. – Joe Apr 24 at 11:57
  • I think RAM was SRAM, because it held all installed software and data, if switched "off" (that is, in sleep mode), and even for some minutes with the batteries pulled out. There might be a low-energy refresh mechanism, though. – the busybee Apr 25 at 11:46
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    @thebusybee The Palm Pilots used SDRAM. I think SRAM of that size would have just been prohibitively expensive. They originally used the SDRAM power-down self refresh mode, which unfortunately wasn't completely reliable in the chips used. So they switched to doing more active refreshes I think, which luckily didn't impact battery life all that much. – Andreas Bombe Apr 25 at 17:35
  • @AndreasBombe Oh, thank you very much for the insights! There are some Palm down the cellar, from Pilot to TungstenT, but I never came to open one. – the busybee Apr 26 at 10:32
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Assorted sources on the internet indicate that the Palm / Pilot models before the Palm III used "PSRAM", or "pseudo-static RAM" for the replaceable onboard memory. This means a device that contains a DRAM, but has the electrical interface of an SRAM, which makes things simpler for the host machine. Those modules also contain the device's ROM, and ROM and (P)SRAM share basically the same interface, other than ROM lacking a write-enable pin.

The book "Hardware Hacking: Have Fun While Voiding Your Warranty" gives the Toshiba TC518512AFT as an example of a RAM chip suitable for upgrading the storage on the Pilot 1000, 5000, and Professional. It also gives schematics for the memory cards -- unfortunately it doesn't include the pinout of the edge connectors, but it does indicate that they're bringing out the PSRAM/ROM signals out directly — 20 address lines, 16 data lines (8-bit PSRAMs are used in pairs), power, and chip select / write enable lines. The only difference between the Pilot 1000/5000 cards and the PalmPilot cards seems to be an increase in the number of chip select lines — and the number of chips.

I don't think the connector is called anything except an "edge connector", with the spacing between trace centers ("pitch") specified.

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I don't recall the Palm-branded PalmOS devices ever supporting any standards other than SDCard for memory expansion, but that was only after several models had been released. The original Pilots had a proprietary memory expansion, the III and VII devices weren't expandable, however the V and later devices did support the SDCard. I think Sony produced some compatible devices as well, but if I remember correctly, they used the proprietary Sony Memory Stick, no SDCard. That being said, the SDcards used in the PalmOS devices are compatible with any device today that uses SDCard (though they're probably way too small to be useful nowadays).

The first clones were the Handspring devices which did have the Springboard expansion slot on the back. These sound a bit more like the form factor you mention, but they were used for more than just memory - there were devices for cellular connections, cameras, I/O, etc. so the connector went beyond standard SODIMM connectivity. As you can see on the pinout I found here, pins 60 and 61 were for microphone connectivity, something that makes it sound definitely proprietary and not a typical RAM connector.

FWIW, I had a III and Tungsten-T3 during the years what I was a PalmOS user, so I never really had much experience with Handspring or any expansion devices like you describe.

UPDATE 2020-05-01: I stand corrected, the original PalmPilot 1000/5000 devices did have the removable back door to a memory expansion slot. Though upon further investigation on these sites, it looks proprietary as the form factor is slightly different from SODIMM but also I can't find any reference to it being anything standardized. At the minimum, it appears that the boards also held ROM.

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  • Here's the pinout for the Springboard expansion slot. It's physically the same as PCMCIA but the pin assignments are different. It's been a while but it appears to be the 68000 system bus plus power and some additional PDA-specific functions (microphone, low battery, etc.). – Alex Hajnal Apr 26 at 4:44
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    The devices I have are an original 3com PalmPilot Professional and a handful of Symbol SPT1500 devices. The cards from both are compatible with each other, and all of these devices were manufactured before Handspring launched. – occipita Apr 30 at 18:53

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