18 Oct
2015
18 Oct
'15
5:37 a.m.
On 2015-10-18 12:37, Rick Murphy wrote:
At 01:22 PM 10/17/2015, David Gesswein wrote:
I decided to look into this a couple of days ago, since the basic
workings of FRTS includes using interrupts, which is not possible if
running under time sharing. That would also imply that it would not be
possible to use F4 under RTS-8, which I had some memory of that it
actually is possible.
To sum things up: The FPP-8 can usually not be used when in timesharing.
First of all, you use IOTs to control the FPP, and all IOTs are trapped
when in user mode. Second, as you note, the FPP-8 uses 15-bit addresses,
which would make it impossible to use with virtual memory.
Also, the interrupt system is not available when in user mode.
However, FRTS actually have code to detect if it is running under RTS-8,
and do not use the interrupt system in that case, but adopts. Also,
since the FPP-8 IOTs are caught by RTS-8, and do not do anything, FRTS
actually believes you are on a system without an FPP-8, even if you
actually have one. So, FRTS will always use the FPP-8 emulator in this
situation.
MULTOS-8 hook in to the same functionality, making FRTS believe it is
running under RTS-8, which means that F4 programs will actually work
under MULTOS-8, including ADVENT. I don't know if ETOS also implements
the bits needed to make it look like OS/8 programs are actually under
RTS-8. If it does, ADVENT should be possible to run under ETOS as well.
Otherwise not.
Finally, as I noted, the FPP-8 is not that possible to use in user mode,
both because of the IOT instructions being caught, and the 15-bit
addressing. However, the FPP-8A have a mode where it only allows memory
accesses within the same field, and will trap out if any memory
reference goes to another field. With some work, and code, I think it
could be possible to actually have access to the FPP-8 from user mode,
if you have an FPP-8A, but I have never tried this, as I lack the hardware.
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 Fri, Oct 16, 2015 at 11:03:51PM -0400, Rick
Murphy wrote:
System users guide pg 4-10. Fortran IV. Real time functions and floating
point processor functions are not currently supported. The internal
device handlers for high speed reader/punch and card reader are not
supported.
Device independent I/O must be used to access these devices.
I don't know if that means the floating point instrutions won't work but
the software emulator fallback will or any attempt to use floating
point will
fail.
The Fortran IV compiler emits FPP code, so what that has to mean is that
you can't use a hardware floating point unit and must use the built-in
emulator. That makes sense, as the FPP code has built-in 15-bit
addresses that won't get swizzled by the ETOS time-sharing option.
Guess I'll try to get a round tuit and bring up ETOS on my PiDP-8 to see
if it can be made to work.