71B MultiMod: MEMORY LOST when changing batteries?

[Dave Britten]

(04-21-2021 03:25 PM)rprosperi Wrote:  Unrelated to the MMod, this behavior varies a lot among various 71B machines (I have several). Some machines will let me casually change batteries (always one at a time) with no ML (when powering-on), others will ML after even < 1 sec of removal.

Installation of additional RAM modules (in both front and CR ports) also can affect this, though not always as simply 'more modules = less time'. Some cannot withstand ANY time with modules installed, others seem OK.

As a general rule, I suggest you always connect a power supply before changing batteries, and also, once new batteries are installed, I recommend you 'roll them' in place, by simply rubbing across the 4 batteries with you fingers, which seems to ensure better contact, before powering on.

Note: If you're new to the 71B, it's important to know that most often when an ML occurs, the contents of IRAM ports are not lost and are preserved intact. I point this out because if you assume that all RAM is lost (as the ML message would seem to imply) you may remove a RAM module, or make other configuration changes, which would then in fact lose the IRAM contents, which otherwise were OK.

What does the 71B use to power the RAM while the batteries are removed? Is it a plain electrolytic cap, a "super-cap", or something else? A few months ago, I bought an old Handspring Visor Neo that couldn't withstand battery removal, and I had to solder in a new super-cap to fix it. I wonder if the same is possible or necessary on the 71B.

Regarding IRAM, it's not possible to edit programs unless they're in main memory, right? Can you merge multiple RAM modules to create one big IRAM? (e.g. I have 3x 4K modules, can I use them as a single 12K IRAM?)

If there's ever a MultiMod 2.0 that also incorporates a nice chunk of battery-backed SRAM, you can definitely put me down for one.