Every time I see one of those evil NiCad batteries, I replace it with a 0.5F supercap.
I have never had an issue with my M100, or with the Olivetti equivalent (number escapes me at the moment) Having said that, the oldest would have been 8 years ago, so I don't have the same 30years of experience regarding leaking characters. Doug On Sun, 17 Mar 2024, 11:44 am Brian K. White, <[email protected]> wrote: > You can run plugged in to the wall for all normal random on/off > operating times without worrying about it too much, IE, all day long for > 8 to 12 hours or whatever, and for multiple days in a row, if unplugged > when turned off. > > And you can leave it plugged in turned on or off overnight for one night > to a few days. > > And you can even get away with exceeding those pretty badly once in a > while. > > What you want to avoid is plugging it in and leaving it plugged in 24/7 > for weeks or months or years, whether it's on or off. > > The harm is the charging circuit that charges the internal nicd battery > soldered on the motherboard. The battery is not a lead/acid or gel cell > that has a float value where it can just stay floating at a certain > value forever, and the charging circuit is not a smart modern battery > manager that knows how to stop charging when the battery is full, it > just keeps on supplying a bit higher voltage than the the cells own > voltage, and current just keeps on flowing backwards through the cell, > and sooner or later this kills the battery by a couple different > possible mechanisms from plain heat & pressure making it leak and cook > off all the electrolyte, to things like the electrolysis process like > electroplating, eating away all of one plate and building gunk up on the > other. > > It's pretty forgiving so you don't have to be super careful. You can > *mostly* never even think about it, and a normal random usage pattern > will just naturally be fine. Just don't plug it in and forget about it > for a year. > > It doesn't touch the AA's and it doesn't matter if the machine is turned > on or turned off. > > Now that you make me run through it all like that, I realise this might > finally be be an actual valid useful reason to install a supercap > instead of a new nimh cell. > > Mostly there is no point, because both a cap and a battery will only > last about the same number of years, and both will start to leak > corrosive juice after about the same number of years. A cap is not > harmed by being allowed to go all the way dead (which a battery is), nor > by being allowed to stay dead for a long time (extra especially bad for > a battery), but even a battery that has been so badly treated still > supplies more standby time than a brand new perfect cap. All in all, no > point. > > But one difference that matters, a cap should not be harmed by the > crudeness of the charging circuit. A cap will just charge up and stop > conducting and won't care about the charging supply at all. No current > will keep flowing through the cap, no cooking or electrolysis etc. > > I have always been very much not in the supercap camp, but this is one > real thing. > > -- > bkw > > On 3/16/24 16:33, Will Senn wrote: > > Wow, Brian! Super clear. Now, I want a REX# :). > > > > When you say that leaving it plugged in will kill the battery, do you > > mean that I should run it off AA batteries most of the time and not my > > 6v 200ma adapter? And the battery you're talking about killing is the > > nicad on the board, right? > > > > Thanks, > > > > Will > > > > > > On 3/16/24 3:21 PM, Brian K. White wrote: > >> I summarize REX as: "An on-board software-controlled option rom > >> library and ram image library." > >> > >> That's the shortest way I've found to say what it does, but that's not > >> the same as saying what it's good for or why you want one. > >> > >> Because of the particular features and limitations of a M100, probably > >> the single most life-improving thing you can do to one is to have > >> TS-DOS in ROM. > >> > >> That one thing addresses a few different pain points. > >> > >> The biggest pain points of a M100 are: > >> > >> - Battery-backed ram only storage. Very little storage, and easily > >> erased or corrupted, either by dead batteries or a software crash. > >> > >> - The way in manages machine-language software. How they all want to > >> run in the same place in ram, yet the OS does not provide very much in > >> the way of automatically moving programs into and out of that spot, so > >> software is always clobbering other software, or you limit yourself to > >> just having a single machine language app installed, or you have to > >> figure out the arcane way to hack the binaries to relocate them to run > >> at different addresses side by side, or you have to keep double copies > >> of binaries so that the running copy can get clobbered and later > >> replaced from the ram file copy... > >> > >> - The main rom provides no binary file transfer other than the > >> cassette. And no *convenient* file transfer even for text. > >> > >> These things combine to make life kind of difficult. For instance you > >> want some better file transfer app, but since you have no binary file > >> transfer to begin with getting the file transfer app itself installed > >> is a pain. Then once it's installed, it consumes precious ram, and is > >> easily broken because of the way machine language apps are are run, > >> and the simplest way to address that is to have a 2nd physical copy in > >> ram, which uses up yet more of that precious 32k. etc. > >> > >> Having any tpdd client at all installed in any form makes transferring > >> files a breeze, including binary files. This somewhat alleviates the > >> small ram problem because you can easily put files away and get them > >> back, as long as your tpdd software stays working. > >> > >> Even better is having a full featured tpdd client like ts-dos instead > >> of teeny, and having it in rom instead of ram. > >> > >> That alleviates all kinds of annoyances. > >> - It consumes almost no ram. > >> - It doesn't require a pain in the neck bootstrap/loader process to > >> get installed. > >> - It isn't subject to being clobbered and needing to be reinstalled > >> because of some other software writing over it or crashing. > >> - It isn't lost after a hard reset or dead batteries. > >> > >> With TS-DOS in rom, you can pick up a totally dead machine, or totally > >> kill your machine with a hard reset on purpose, or suffer a total ram > >> corruption from buggy software, and with just "CALL 63012" you are up > >> and running again, connect to a computer and pull down files. > >> > >> But even though this makes a lot of things a lot better, this still > >> needs a computer and serial cable. The tpdd client just makes it so > >> that you can effortlessly connect to a pc and move files back & forth, > >> and having it in rom just means you can effortlessly always have the > >> tpdd client regardless of crashes or dead batteries. > >> > >> That still leaves a couple things that could be better: > >> - If you had a plain ts-dos option rom, it means you can't use any > >> other option rom because the single socket is occupied already by > ts-dos. > >> - You still need a serial cable and pc (or a real tpdd drive or a > >> Backpack or PDDuino) to actually get the files from somewhere / put > >> them somewhere. > >> > >> REX gives you ts-dos in rom just for starters. It gives you ts-dos in > >> rom which just that right there alleviates several things above, but > >> also: > >> > >> - all other options roms besides ts-dos > >> - full ram image backups > >> - all on-device self-contained with no computer or serial cable needed > >> (after initial loading) > >> - impervious to dead batteries or resets or crashes > >> > >> And although you do need a computer to install option rom images onto > >> the rex one time, ts-dos in particular is pre-installed, so that > >> single most-needed one never needs even the initial one-time install > >> from a computer. Only all the other roms need to be loaded from a pc > >> once. And the loading process is easy, because REXMGR uses tpdd > >> protocol internally to pull the rom images from a pc. No > >> bootstrapper/loader procedure. > >> > >> The other option roms give you mostly a few different office software > >> kits, ie spreadsheets and word processors, and a few other things like > >> there is a FORTH rom and an assembler/debugger/renumberer. > >> > >> The ram image backups give you essentially more copies of 32k ram. It > >> helps a few different ways: > >> - you can physically hold more than 32k of apps or data. > >> - you can recover from a dead battery or reset or corrupted ram from > >> crashed software by restoring a ram image. > >> > >> There are something like 30 or so available slots, and each slot can > >> be either an option rom or a ram image. That's a lot. > >> > >> All without a computer. In the coffee shop, on the train etc, just > >> recover from dead zero in a few seconds. Just "Call 63012" and away > >> you go, all interactive app and menu driven after that. > >> > >> So that is why you want a REX of any stripe, REX Classic, REX#, or > >> REXCPM. > >> > >> Now for REXCPM in particular.... > >> > >> Those particular advantages are something the REXCPM is less good for. > >> > >> REXCPM does give you all of that, but only as long as the M100 > >> internal battery is not dead and the REXCPM and bus adapter board > >> remain installed in both sockets. > >> > >> You can recover from software crashes that scramble the ram, and from > >> intentional hard resets that wipe all ram (ctrl-break-reset), but not > >> from dead batteries or switching off the memory power switch on the > >> bottom for more than a few minutes, or removing the device from the > >> m100 for more than a few minutes. > >> > >> If the M100 internal battery runs out, or you uninstall it for more > >> than a few minutes (you do get a pretty good grace period of several > >> minutes, maybe even over 10 minutes) then you have to reload the > >> REXCPM from scratch as you just experienced. If you had a REX Classic > >> or REX# instead of REXCPM, all you would have done is type "call > >> 63012" and you'd be all back up & running. No pc, no "37 easy steps". > >> Done. And to remember "call 63012" just write it on a sticker or > >> label-maker on the bottom. Put it on the underside of the option rom > >> or battery cover if you want to hide it but then you have to at least > >> remember that it's there. > >> > >> I did make a "UPS" for REXCPM that should keep it alive for a few > >> years, but it's pretty involved to build and ultimately hard to justify. > >> I don't pretend it's practical for most people, but it does work and > >> exists. > >> https://github.com/bkw777/REXCPM_UPS > >> > >> You have to buy the parts from digikey or mouser etc, order pcbs from > >> elecrow or oshpark etc, and then it's a pretty fiddly soldering job, > >> and it ends up costing as much or more than the rexcpm itself just to > >> give it a battery. And for all that, I think I only estimated 6 months > >> per cell x 4 cells = 2 years, but that's after the M100's own > >> batteries run out, and if you have fresh alkaline AA's and a charged > >> internal battery, the M100 itself can last anywhere from a few months > >> to a year. So maybe up to 3 years? > >> > >> A better long-term solution would be a keeper. You remove the rexcpm > >> and plug it in to something with socket and a big battery. But that > >> doesn't help with one that's installed in a machine. You'd need to > >> remove it from the machine to put it in the keeper. Plus the molex > >> sockets are no longer made. There are a few around available still but > >> this would be a wasteful way to use one up instead of keeping them to > >> repair machines. Really, for the long term like over 5 years, it's > >> probably more practical to just let it die and reload it. With a > >> convenient bootstrapper and tpdd server on a pc, it only takes a few > >> minutes to reload a rexcpm from scratch. It's several steps that > >> requires a cheat sheet to follow, but none are very difficult or long. > >> The hard part is just deciphering the original directions to figure > >> out what actually are the steps you need to do. > >> > >> So all in all, I'm not sure how necessary the ups is. It's probably > >> more practical to just do 2 things to live a happy life with a REXCPM: > >> > >> 1 - Keep it installed in a machine. And keep that machine charged. > >> (Unfortunately, you can't just lave the machine plugged in to the wall > >> 24/7 for months, that will cook the internal battery.) > >> > >> 2 - Get good at reinstalling it. It's several steps, but it's possible > >> to write a little cheat sheet that is easier to follow than the full > >> original documentation. And none of the steps are very difficult or > >> long. You don't even need the cheat sheet after a few runs through. > >> > >> If you aren't specifically wanting to run CP/M then I always say a > >> REX# is far more practical. REX# is an nvram device that acts like a > rom. > >> > >> Instead of ever needing to recover the REX, the REX is what recovers > >> your M100. > >> > > > > -- > bkw > >
