some additions from
http://www.nedopc.com/zxevo/rom/evo_reset_service.pdf4. Updating FLASH ROM
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Since version 0.46 is added feature updating user's "Custom ROM" by the size 64 KB. Order of pages in "Custom ROM": "Basic48", "TR-DOS", "Basic128", "Service". An obligatory condition - presence of 2 byte with codes #00, #C9 at offset #3D2F in "Service" page (the reset will be redirected into this page at an option choice "Custom ROM").
Updating is possible for whole ROM (512 kilobyte) or 64 kilobytes for "Custom ROM". Files panel will be displaying *.ROM file only is size 512K (in case whole ROM update) or 64K (in case "Custom ROM" update).
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6. A choice of alternative ROM
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Since version 0.46 is added feature of choice of user's "Custom ROM" (with independent update). The size of this ROM 64Кб. Order of pages in "Custom ROM": "Basic48", "TR-DOS", "Basic128", "Service". The reset will be redirected into "Service" page through entry point at offset #3D2F.
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Oh, my English...