24 Nov
2015
24 Nov
'15
1:01 a.m.
On 11/24/2015 12:46 AM, Johnny Billquist wrote:
On 2015-11-23 20:30, David Bridgham wrote:
22-bit addressing is not possible on the Unibus. The RH70, which is
the massbus controller for the 11/70 do 22-bit addressing, but it
manages that by not sitting on the Unibus.
The RH11 has 'paging' on the controller. It can translate between Unibus
addresses and memory addresses.
For a
classic/straightforward programming interface, the Massbus
disks (RP04 and successors) are a good choice. That will take
you just over 500 MB, if you emulate the layout of the RP07.
Current thinking (at least my current thinking) is RK11 first then
probably RP11, both optionally extended to support Q22 addresses.
Also something we're calling the RQ11 which will be our "native"
interface with variable sized disks with a 32-bit linear block
address giving 2TB disks for those who are willing and able to
write their own device drivers. Finally, most likely the RH11 for
some Massbus disks with 22-bit addressing. After that, I'm
thinking to call it good and move on to other projects though I'm
certainly willing to talk to anyone who has a particular disk
controller they want to implement. Your native interface have the additional problem that
in addition to
requiring people to write their own device driver for any OS usage,
it will be rather difficult to get booting from it, since that
require special support.
RK11 and RP11, while fairly simple, are also very small devices. Is
that useful for anything beyond it being a fun exercise? Massbus is a
bit more useful, as it at least gives some larger devices, but you
need to implement each device. Each has its own device identity, with
its own geometry, which you need to support. There is some rather
non-generic things around massbus.
Johnny
Rob.