24 Nov
2015
24 Nov
'15
2:13 a.m.
On 2015-11-24 10:01, Rob Doyle wrote:
On 11/24/2015 12:46 AM, Johnny Billquist wrote:
I don't understand what you mean by that.
The RH11 do DMA, just like all other disk controllers I know of.
The Unibus only have 18 address bits. Thus, it is impossible to do
22-bit addressing for any controller on the Unibus. No matter what the
controller do internally.
Unibus machines with a 22-bit memory address use soemthing called a
Unibus map to translate the 18-bit Unibus address into a 22-bit memory
address when you perform DMA.
The Unibus map is a part of the computer, and the controller on the
Unibus do not even know it exists.
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
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.