23 Nov
2015
23 Nov
'15
11:46 p.m.
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.
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
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt at softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
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.