I didn't want to say anything until I had read more and also waited to see if others experience the same problem. However, I must now report I am having no luck with the new BIOS in "Altirra". The problem is a little similar to what MARIO130XE reported, except without the boot-cycle - I think.
My configuration at the "Altirra" levels:
Devices: (P:) Printer, (H:) Host Device
Firmware: Stock '800XL and early 65XE' as verified by the 'Atari ROM Checker.jar' utility (MD5:06DAAC977823773A3EEA3422FD26A703)
Acceleration: SIO Override Detection, P: (Printer CIO), CIO Burst Transfers
Memory Config: Ultimate 1MB (obviously!)
Video: PAL, VBXE (FX1.24 core), No Artifacting, Standard Video,
Audio: Stereo, Non-linear Mixing, Channels 1-4
Hard Disk: SIDE2.
I use the 'UFlash.XEX' that comes with the v0.24 beta release, and update only the 'BIOS' 'PBI BIOS' entries. Everything else is identical to the old release, including SDX447, ROM slots, GAME slots and the rest. When I first 'Reboot' from inside 'UFlash', immediately after flashing the new ROM code and after setting the 'SDX size at 256k' the simulation seems to work properly. However, once I 'System Reset+Help' up to the BIOS menu, update the new settings to the correct values (where possible) and then use the 'Save Changes and Boot' option I simply get a black screen. Perhaps this is actually is the same 'boot cycle' that MARIO130XE experienced? All I can do is press 'Help', which instantly brings back the BIOS Menu. Nothing changes if I cold reset "Altirra" nor indeed exit the emulator altogether and restart - after saving the new ROM image of course and telling "Altirra" to use it by default.
Interestingly, when I enter the "System Clock and Features" menu the 'VBXE' entry is both greyed out and set at disabled despite being enabled and unchanged since before the reflash. Also strange is that, despite using the stock XL BIOS firmware at the emulator level, the "System Information" menu claims the machine is a 'XEGS (PAL)' and that again the 'VBXE Core' is 'Not Present'.
I have included the ROM images I am using; 'v2.0' before re-flashing and 'v2.4' afterwards.
Scratch all that. A little irritated, I scrubbed over my whole Altirra installation and copied fresh OS ROMS and the works along with a new copy of the recent 'test 18'. I clearly had some kind of Frankenstein's monster of builds in place because after that clean start the BIOS is now working properly as it should and no longer hangs at a black screen. It also correctly identifies the VBXE... Seeing as "Altirra" is pretty much self-contained it is odd how that might have happened; one way or another however I clearly had a corrupted build. Perhaps I only thought I had updated the other week, but I am pretty sure I did. Bugger - there's about a six days of dithering around wasted!!! Nevermind. Whatever the case the new version of "Altirra" and new the "Ultimate1MB" BIOS seem to work properly. I am very tempted to flash this to the real hardware... But I think I will still wait for my USB programmer to come.