On 2015-07-27 08:16, Vincent Slyngstad wrote:
From: Brian L. Stuart: Sunday, July 26, 2015 8:51 PM
Running the GTF instruction on my 8/M
when the inhibit FF is set results in a 0 in AC3.
Curiouser.
To Stuart - are you sure your code does it right. Could you post it?
Furthermore,
both simh and Doug Jones' emulator omit the interrupt inhibit
bit in the GTF instruction. In fact Dr Jones' emulator has a /*?*/
comment in the code. Does anyone know the origin of this
discrepancy? Was the behavior the same on pre-Omnibus
versions of the 8, or did earlier address extensions include
that bit in the GTF result?
I don't believe that the pre-Omnibus memory extensions implement GTF.
Correct. Pre-Omnibus machines had a rather different set of instructions
in in those opcodes.
The IM6100 datasheet says bits 3 and 5-11 are under control of the
memory extension. Reading the description for the IM6102, it says GTF
will place INT INH in AC3.
The HD6210 datasheet says bit 3 is the PWRON flag for GTF, and bit 3 is
unchanged by RIB.
The design of the KT8A is sufficiently opaque that I haven't figured out
yet how GTF works there.
he KT8A is very different. If someone is curious, the manuals do explain
it, or ask and I can try and explain it as well.
But essentially, AC3 in GTF in the KT8A is targeted for use to detect if
an IOT was executed while a delayed CIF was in effect in user mode.
Essentially saying to the OS that the user mode program is barfed and
cannot be restarted.
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: b...@softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
