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

[Clem Cole via TUHS]

Well, more importantly, is the hardware in it.  TOPS-20 ran on the
ECL-based KL10-D [2040/2050] and KL10-E [2060/2065]  and AMD 2900 bit-slide
KS10 [2020] Besides the earlier KA and KI variants, TOPS-10 ran on the
KL10-D [1090], KL10-PV [1091], and the  KL10-E [1091].  The KL10-D could
support dual and tri CPUs [1090 SMP and Tri-SMP].

The KL10 series used something called the E-bus (executing bus) that
communicated with the MASSBUS, the I-bus (KA/KI10 style for peripherals
developed for earlier PDP-10s), and a DMA memory bus called the C-bus
(channel bus), as well as the front-end PDP-11 (and its Unibus). For the
KS10, there was its memory bus of course, but it supplied a C-bus
implementation and a Unibus.

The 1091 and 2060 used the same processor logic, but had some differences,
such as the PDP-11/40 [called the DL10 on a 1090 and the DTE20 on the
2060]. The DL10 ran a system called RSX-20, while the DTE20 ran a hacked
version of RSX-11M called DN20.

Because TOPS-10 and TOPS-20 used different paging and context-switching
schemes, different microcode was loaded into the KL10-E's microstore.  The
1091 loaded microcode optimized for the TOPS-10 memory model and supported
its "monitor calls." The 2060 loaded microcode that implemented the
BBN-style paging and "JSYS" instructions required for TOPS-20.

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.