Some thoughts...
The storage is an IDE Flash Disk, AKA Disk On Module. It has a 44 pin female header connector, same electrical interface as a 2.5" IDE hard drive. They're available dirt cheap in sizes from 64 megabytes to 2 gigabytes, not so cheap in 4 and 8 gigabytes...
You can also use a compact flash (CF) card with a purely mechanical adapter (CF can speak IDE interface language). They are cheap but I think DOM can do more I/O transactions per second. Another idea: Instead of EMS, you could use good old XMS to make a big ramdisk and then copy everything there on boot. Assuming that you do not plan to modify files on the machine - modifications would be lost each time when you shut down or reboot without copying data back from the ramdisk to the flash disk. The ramdisk would be as fast as the EMS library of G files in your old software, but would not need EMS. In my opinion, XMS drivers are more "tame" to use compared to EMS drivers. If your old software supports EMS 4.0, then you would not need a 64k page window. This is what the NOEMS option of EMS drivers does: It skips the creation of the window. Software which understands version 4.0 of EMS can still use EMS without needing a large fixed window. With DOS in HMA and drivers (if safe and not too fragmented) in UMB, you will have a lot of low memory available. So depending on how large those G-Code files are, things should be okay. Note that you can use UMBPCI to have raw UMB without the hassles of configuring EMS right. Also, UMBPCI is still maintained for support of many mainboard types. Regards, Eric
DOS or FreeDOS, I just want to get the thing to boot off the IDE flash module and run with as much EMS memory as it can. The software I need to run is made to run on anything with DOS, and EMS, and a serial port, all the way back to the 5150 IBM PC. Don't need any XMS, it loads the G-Code files into EMS, if available. Otherwise it uses whatever low memory is available and files too large to fit must be cut up with the splitter/linker utility.
Hopefully the WYSE Sx0 series thin client's memory map isn't all fragmented up like circa 1995 and newer laptops. They don't have a large enough contiguous RAM space to put the 64K EMS paging window.
If this can be made to work I'll write up a how-to so other PLM2000 CNC mill owners can setup a tiny controller box and ditch the big PC. The control computer does zero computing of things like curves. It just sends G-Code to the mill and monitors return communications for encoder counts, limit switch activation and stop messages from exceeding torque limits. The servo controller in the mill does the heavy lifting.
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