Hello Jan.
Mine is working at 256mb and failing at >257mb. 256mb lets me install and is happy. Memory detection is not working past 256mb. I am using the patched ROM.
$ md5sum ka655x.bin ka655x.bin_old
083ffdc5b57a9c230a2c6cca856607f8 ka655x.bin
ac2bd5976b9a7c188d394a6a036bcfcf ka655x.bin_old
ka655x.bin_old (unpatched) only recognises 16/64/96/128/256mb and won't do >256mb.
sim> show ver
MicroVAX 3900 simulator V4.0-0 Current
[...]
git commit id: 6fdc4474
git commit time: 2020-07-24T19:12:15-07:00
256mb:
>>>show mem/full
Memory 0: 00000000 to 00FFFFFF, 16MB, 0 bad pages
Memory 1: 01000000 to 01FFFFFF, 16MB, 0 bad pages
Memory 2: 02000000 to 02FFFFFF, 16MB, 0 bad pages
Memory 3: 03000000 to 03FFFFFF, 16MB, 0 bad pages
Total of 256MB, 0 bad pages, 128 reserved pages
Memory Bitmap
-03FF0000 to 03FF3FFF, 32 pages
Console Scratch Area
-03FF4000 to 03FF7FFF, 32 pages
Qbus Map
-03FF8000 to 03FFFFFF, 64 pages
Scan of Bad Pages
>>>
257mb:
>>>show mem/full
Memory 0: 00000000 to 00FFFFFF, 16MB, 0 bad pages
Total of 16MB, 0 bad pages, 104 reserved pages
Memory Bitmap
-00FF3000 to 00FF3FFF, 8 pages
Console Scratch Area
-00FF4000 to 00FF7FFF, 32 pages
Qbus Map
-00FF8000 to 00FFFFFF, 64 pages
Scan of Bad Pages
>>>
Regards,
Al Boyanich