Interesting. Is this some sort of latching switch on memory address lines? You set it into some specific modes and it transparently (to the CPU) switches memory banks based on the mode it's in? The EMS chip itself must only be able to address banks of 256K, and you can't allow the motherboard to address multiple banks at once, so you're stuck making the motherboard think it has 256K, and then you just point that "window" to your "real" RAM.

Everything I just said is likely all the obvious stuff you already figured out. Still.. interesting. I wonder if it has any uses other than DesqView.

I suppose the point is specifically to run each program in one of those banks so that you can have more memory usage than conventional allows but programs all think it's conventional?

I know later EMM reserves low memory and swaps in high memory pages one at a time, so I guess this is sort of like that in hardware, but it has to switch the entire memory bank?

This looks the same as the "ALL Chargecard". It's pretty nifty, but only worth that price to collectors. Any 386 or 486 upgrade module would provided all the benefits of these chips and more.

Thank you very much for the replies!

I don't own that thing, though. I'm happy so far with my humble AST Rampage 286. ;)

Just saw that auction by accident and thought it's very interesting.

And since another type of CPU daughtercard was also discussed just recently,
I thought I should let you know about this one..

Quick update. Sorry for necro-ing my own thread here!

Found drivers for all chargecard by accident. There seems to be a PC-MOS/386 driver, too! 🙂
Perhaps that's one of those supported interposer cards that allow more memory and advanced, 386-like multitasking on PC-MOS?

Directory MSDOS/ALLCHARG/ Filename Type Length Date Description ============================================== _CHARGE.AR […]
Show full quote

Directory MSDOS/ALLCHARG/
Filename Type Length Date Description
==============================================
_CHARGE.ARC B 2050 890808 PC-MOS/386 driver for ALL CHARGECARD
ALLCRDSY.ARC B 165648 890808 SYSTEM Files for ALL CARD AT1/M for the PC/XT
ALLMOS.ARC B 166955 890808 960K DOS files for ALL CHARGECARD ver. C1.09b
ALLUTIL.ARC B 67778 890808 Video patches for ALL CHARGECARD & ALL CARD
ALMNC280.ZIP B 174370 911226 System information display for ALL CHARGECARD
CHARGE.ARC B 2065 890808 MultiLink Advanced driver for ALL CHARGECARD
LDRSC280.ZIP B 116180 911226 EMS loaders for ALLEMM4 CHARGECARD software
NEWC280.ZIP B 135881 911226 The complete ALL CHARGECARD software ver C2.80
SOCKET.ARC B 2889 890808 Types of 80286 Computers & their socket types
VIDEO.ARC B 24484 890808 Files making up the ALLCHARGE Video Patch Kit

Source: http://cd.textfiles.com/simtel0692/INDEX.TXT

Great job! Do you have any All Chargecards to sell me?