digger wrote on 2025-03-03, 13:30:

Jo22 wrote on 2025-03-03, 13:04:

^DOS=HIGH does have an effect on an PC/XT in MS-DOS 6.22, if USE!UMB.SYS was being loaded. I tried myself, with a non-intelligen […]
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^DOS=HIGH does have an effect on an PC/XT in MS-DOS 6.22, if USE!UMB.SYS was being loaded. I tried myself, with a non-intelligent UMB card.
I tried it together with UMB setting: DOS=HIGH, UMB

Of course, there's no HMA in XTs, but MS-DOS 6.22 does upload more DOS data into UMB if the HIGH setting is set additionally.
It will also complain with a message similar to "HMA not available, use lower memory", which can be ignored.

Cool! I didn't know that. Thanks for sharing that tip!

Hi again, I did forget something! I had to load STOPMAX.SYS on top of config.sys as a device driver, which supressed DOS to auto-load into non-existant HMA (on an PC/XT).
Otherwise, without the driver, the MEM command would be confused and DOS would end up at the bottom of conventional memory.
I checked that with CheckIt! v3. With the STOPMAX/DOSMAX, most of DOS kernal moved correctly into UMBs, leaving merely 9KB in conventional memory.

Hi,

do i need to solder a PSRAM to teensy or does it work without one too?

Thanks