I finished making a new device driver ('XX') for RT11 V4 that uses my
RXV11 emulator board.

The 'XX' driver differs from the DX driver in the following ways:

- Capacity is 100000(octal) blocks (16 MB!). It could easily be made to
handle any size that the OS supports, but 16 MB seems plenty big enough.
I'm guessing that RT only goes up to 32 MB (177777 blocks)??
- Transfer size is 512 bytes instead of 128 bytes.
- No interleaving.

No hardware changes in the RXV11 emulator.
The code on the laptop can be switched between DX and XX mode with an
INI file setting.

The XX driver/disk can be booted from RT11. In the laptop code, I tried
making Unit 0 behave as a DX, while Unit 1 was an XX. It almost worked,
but it hung because both drivers are using the same CSR and vector, so
the interrupts get tangled up. I think it could be made to work if I
supported separate vectors for the two drivers, and as long as the
access to the CSR was always single-threaded... But I don't think I'll
bother to try that, since I've got both of them working separately now.
I'm just finishing up a hardware boot routine for the XX device, which
I'll put in the EEPROM.

This RXV emulator project has finished up just in time - my RL02 is
getting flaky (read errors, fault light comes on occasionally). The RL
is my only other bootable disk, except for a PDT-150. Now that the
emulator is working well, I have very little reason to power up the
RL02.

Next project: I'm thinking maybe I should build a Unibus version of the
HW, to use with my 11/05 (the only Unibus machine I have).

Pete
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