Ramsey not being initialised

[darrenfreeman]

I am poking around at the Ramsey control register, $DE0003. I was wondering what options are enabled during my DiagROM motherboard memtests.

I enabled page mode, bit 0, then ran a memtest. Boom, system crashed. (Looks like my RAM is not all static column.) Ctrl-A-A reset didn't return the system to normal operation, I had to power cycle. So DiagROM is not initialising Ramsey to a known state. (And the schematic has no reset line to this chip.)

I don't think DiagROM can guess at the full default value once it's been changed, since the default is loaded from pins on the chip, which DiagROM doesn't have visibility of. But we know that some bits are always cleared on power on, for example page mode. Leaving page mode enabled is enough to crash DiagROM, so it's necessary to always disable it at startup.

What I would request as an additional feature, is display the current Ramsey register value in the system info screen, and the Ramsey revision ID at $DE0043. Display some text about whether Page/Burst/etc. are enabled.

Then add a tool under memory tests, which performs the check for static column RAM at each 1 MB bank of motherboard RAM. (Details in the A4000 service addendum under Ramsey.) If all banks are static column, ask if the user wants to enable page mode at the end of this test. Otherwise it's a bit of a chore to work out which SIMMs are static column.

[darrenfreeman]

Oh, I've worked out why it crashes and won't recover - I had maprom enabled! So almost certainly the memory test managed to trash the ROM overlay.

Without maprom, the memtest of fastmem will fail immediately, and not even show any text apart from press any key to continue. But then I can turn off page mode and run it again, and all is well. I can still confirm that Ramsey is not being initialised, as page mode remains across reboots.