XTMax documentation

[eparadis]

Hi! I'm wondering where the documentation for the XTMax is located?

This repo has the .ino which clearly needs to go onto the board, but other than that - what settings are required? Is there a debug HID serial device on the USB port? What about the Ethernet adapter? I was going to load up the Arduino IDE to download the .ino, but I just remembered that Teensys are weird and need their own thing, don't they?

The MicroCoreLabs blog has only a single post which doesn't explain how to set anything up. And the .ino file has no notes in it to explain what board settings are expected.

If you could add a Wiki to this github repo, it could provide a place to document all of this. It doesn't seem like the code changes often, so it would be easy to keep up to date.

I bought the complete kit back in January and only now have time to make use of it. Picking it up today I realized all I have is the hardware in a plastic bag, exactly as it came in the mail, with a label saying "XTMax 2026-01-10".

[pawosm-arm]

I'm also interested in the documentation. I've bought an XTMax on Ebay, and the seller warned me I need to solder in the memory chips on the back of the Teensy. Which ones? Does XTMax need both PSRAM and Flash soldered in on the back of the Teensy? Any recommendation on what chips would be a sufficient option to solder them in?
I'd like to try several scenarios:

• UMB and EMS only: could it work without claiming any address space for BIOS? (EDIT: yes, the .ino file can be modified to get rid of the BIOS entirely)
• UMB and EMS and bootable disk partition on an SD Card: is there any challenge in preparing an SD Card for this? Preferably, I'd like to be able to boot FreeDOS and ELKS, but it may be too challenging to do it from one SD Card, so swapping cards is also an option.

[pawosm-arm]

I'm also interested in the documentation. I've bought an XTMax on Ebay, and the seller warned me I need to solder in the memory chips on the back of the Teensy. Which ones? Does XTMax need both PSRAM and Flash soldered in on the back of the Teensy? Any recommendation on what chips would be a sufficient option to solder them in? I'd like to try several scenarios:

• UMB and EMS only: could it work without claiming any address space for BIOS?
• UMB and EMS and bootable disk partition on an SD Card: is there any challenge in preparing an SD Card for this? Preferably, I'd like to be able to boot FreeDOS and ELKS, but it may be too challenging to do it from one SD Card, so swapping cards is also an option.

Actually, this has turned out to be fairly easy. I've used Arduino IDE to flash Teensy. Also I've modified the .ino file to get rid of any bootrom stuff from it and recompiled it. And it did the job, no resource taken.

EDIT: eventually, I've found a free 2kB chunk in the upper address space of that machine, so I could use it for the bootrom. As a result, I could revert my brutal changes. Still works OK.

[pawosm-arm]

After two days of testing it, I'd share my summary:

• I've bought XTMax primarily to replace the two lotech's cards (one for UMB and one for EMS) that were occupying two of the precious ISA8 slots in my Amstrad PC2086. And for this, XTMax does its job quite well. Finally I could install my ISA8 network card back into the machine.
• Before XTMax, I've tried PicoMEM, and it didn't meet my requirements: it needed a way too big piece of the upper address space for its BIOS. In case of XTMax, the BIOS is merely 2kB, and even that can be easily disposed if one knows what to edit in the .ino file, and recompile it in the Arduino IDE.
• Despite lack of any formal documentation, I've found the process doable.

Advantages:

• it does the job

Disadvantages:

• there are problems with the EMS driver when 4DOS is using EMS for swapping; according to AI, the XTEMM driver is not fully compatible with EMS 4.0, despite advertising so (EDIT: even forcing the EMS 3.2 protocol support on the XTEMM driver does not help!)
• the XTEMM driver is much bigger than the lotech's LTEMM driver; when loaded into UMB it occupies so much space that the packet driver for the network card needs to be loaded low taking the precious space there; (EDIT: if one knows how to recompile it, reducing the value of the PAGE_MAX constant results in a smaller XTEMM driver; eventually I was able to fit all the drivers in UMB leaving decent amount of the main memory for the DOS programs)
• the QNX1.2 operating system cannot be booted from floppy when the XTMax card is installed; funnily, the ELKS operating system can be booted from floppy without any problems! (EDIT: success! I've pruned everything about the SdCard and SD_BASE from the .ino file and now QNX1.2 boots from floppy again! Could XTMax's SDCard subsystem resemble an MFM controller somehow? Anyway, I wanted to use XTMax along with XTIDE, and now I'm having all that I needed).

Despite the disadvantages, I've decided to keep XTMax in this machine, as it solves a bigger problem than a sum of the problems it causes.