[TUHS] porting to different systems, Bootstrapping UNIX - how was it done

[Aron Insinga via TUHS]

Your comments are interesting.  Do you have references?

In particular, I do not believe the KS10 ever emulated the PDP-11 or the 
Intel 8080, or ran RT-11.  (Unless you know someone who did that as a 
hack?)  The microcode here shows the power-up sequence at listing source 
lines 2148 (0:) and 7843 (PWRON:):

https://archive.org/details/bitsavers_decpdp10KS_21955535/mode/1up

The KS10 included a real 8080 as the front-end processor.

In manufacturing, so that certain diagnostics could control the machine 
under test, a serial line from a KL10, which ran the diagnostic program, 
was connected to the 8080.  Through the 8080, the diagnostic could 
(among other things) load microcode into the KS10, single-step the KS10, 
and read the micro-PC.

(There wasn't a direct 32-bit data output that could be sampled, so in 
MSDPM (for the data paths to memory, DPM) board, a microcode snippet 
branched to one of two locations based on 1 bit, the diagnostic read the 
micro PC to find the location to see what the bit was, and the snippet 
shifted the data to get the next bit.  I debugged that sitting on the 
floor (I guess I had the DPE board on an extender) and used a DVM to 
check the bit's value and then reached up to the LA36 console to hit 
return and execute the next step.  (Return repeated the last command.)  
We should have put the KS10 protos up on concrete blocks like they did 
in TW for the Comet protos, although I think the KS10 cabinets were 
taller to start with.

The KS10 data path execution (DPE board) had 10 AM2901 bit slice chips, 
with 2 bits extra on each end, so the left and right halfwords were 
divided between chips and could be clocked separately.

The DPM board had bunch of (IIRC Fujitsu 10ns but this was long ago) 
SRAMs along with the 10-bit exponent arithmetic datapath logic (not done 
with AMD chips) that wouldn't fit on the DPE board.

The KS10's microsequencer was custom built and did not use the 
AM2900-family chip.  I don't recall why.

As for the KL10:

The standard KL10 front-end PDP-11 operating system was RSX-20F (F for 
front end).  However, when the machines started shipping, it wasn't 
ready, so temporarily they used a different, small operating system, 
KLDCP (the KL Diagnostic Control Program) written by the Large Systems 
Diagnostics Group in MR1-2 for, well, running diagnostics programs.

https://archive.org/details/bitsavers_decpdp10KLaintenanceGuideVolume2Rev3Apr85_21152180/page/n5/mode/1up?q=kldcp
https://archive.org/details/bitsavers_decpdp10KLaintenanceGuideVolume2Rev3Apr85_21152180/page/n154/mode/1up?q=kldcp

https://f6.erista.me/files/bitsavers/scandocs.trailing-edge.com/rsx20f-aa-h213a-tk.pdf

(I was hired by DEC for the Large Systems Diagnostics Group in MR1-2 to 
modify KLDCP for a new machine, I think it was Dolphin.  When that 
project suffered a design setback, I worked on the KS10 STIRS diagnostic 
[MSDPM, mentioned above] and the VAX-11/750 [Comet] "CPU Cluster" 
Exerciser [NOT related to VAXcluster] for character string and 
interlocked queue instructions.)

- Aron

On 3/24/26 11:14, Clem Cole via TUHS wrote:
> [...]
> In the 2020 model, in addition to the core KL10 emulation, the AMD bitslice
> microcode also emulated the PDP-11 and the Intel 8080.   This microcode was
> the SW equivalent of the original 11/34, which used the 8080 as its front
> console.  At boot time, the KS10 ran RT11 from either its own floppy disk
> or from the system disk.  This version of RT11 could run diagnostics and
> load the OS [originally TOPS-20, but eventually Version 7.01 could execute
> on a KS10 too].  At some point after the OS was loaded, the microcode
> switched to emulate KL10.  Unlike KL10-E's the console terminal via the
> PDP-11 front-end, for the KS10 the console's UART was attached ti main
> processor [what I don't know is after the microcode swap from PDP-11/8080
> mode into PDP-10 mode, how console communicated with the OS - i.e., was it
> just part of TOPS-20 or did the TOPS-20 use the same interface as the KL's
> and thus the microcoded PDP-11 running RT11, would have actually push the
> bits to the UART.