6152 Crossbow Adapter
@8ff7h "RISC coprocessor card"
edsrpc.dgs RISC Processor Card
6152 Reference Diskette *.IMD ??? Contains extracted files
Back to 6152 Academic System
System was housed in a Model 60, 1MB standard on the 6152
6152 "Crossbow" Adapter
Base images courtesy of William R. Walsh.
headers for ???
for memory card
Y2 is probably the
MCA bus oscillator
6152 Memory Daughter Card
There are three different memory sizes
available, 2, 4, and 8MB. From this, I posit that the
Crossbow supports 256K, 512K, and 1MB 30 pin SIMMs.
Further, note there are five SIMMs per bank. I believe
that one SIMM per bank provides ECC, like that on the
7568 Gearbox systems.
SIMMs in the great William R. Walsh psychadelic retro
machine were TI TM4256OU-12L with 9x TMS4256FML -12
chips per SIMM.
Multiple 6152 CPU Cards
|> In comp.sys.ibm.pc.rt article
<Ffirstname.lastname@example.org>, email@example.com (Dan
|> :The Dec. '88 Release of AOS 4.3 supports 2 CPUs in
and RT 6152. I do not know if IBM every released any
instructions although I vaguely remember seeing them drift
by some where. If memory serves, one also needs a
modified version of the 6152 configuration diskette (the
one with the diagnostics) so the bus addresses of the
second CPU card can be set. One CPU could be used to
run the X server leaving the other for more useful
| Is there any other configuration
possible? I'm somewhat more interested in
distributed computing applications, and doubling your
processing power is always nice. :-)
Aha, somebody finally noticed that! I had
intended to post this quite a while back but as usual,
until somebody brought it up I had forgotten about it. I
had sent out a beta-test of these instructions which was
probably what Dan had seen, but hadn't heard back
anything so it just slipped until now.
Please note that the multiple cpu stuff is
completely UNSUPPORTED by IBM - it was a personal
project that was sufficently far advanced to get code
into the product but was much too late for the
documentation and testing required for a supported
feature. This feature is not exactly secret as it was
demo'ed at the fall 1988 COMDEX as a technology demo
with the two Risc bus masters running BSD 4.3 on top of
There is also a paper that I'm going to
present at the IBM internal Unix conference next week,
as it is not IBM CONFIDENTIAL I hope that I can also
post that here as well. In any case, if anybody goes
attempt to get a multiple-cpu system going please send
me email with the results.
In any case here are some notes on how it
is implemented followed by the instructions for how one
builds a multi-cpu IBM 6152 system. Enjoy! Again - this
is NOT a suported feature - use at your own risk etc.
Multiple CPU Architecture for
- processors run independently, each runs its own copy
of IBM 4.3/6152.
- primary cpu (cpu 0) owns real devices (lan, printer,
tape, asy, etc)
- all cpu's share disks (HD, FD, optical) but only 1 cpu
writes to a given HD partition.
- supports 1 or 2 additional processor cards, easiest
case is 2 (total) cards each of which has its "own"
- access to "other" processor's disk is via read-only
mount, or via NFS.
- I/O support program (unix.exe) runs under DOS or OS/2
which handles disk and most other I/O.
- based on PS/2 model 60 and runs on model 80.
- a software "microchannel" device implements a network
connection between cpu's. The primary cpu acts as a
gateway to connect the secondary cpu's to other
- Unix drivers exist to allow other processor's memory
to be accessed and the CPU's to be controlled.
- minimal Unix kernel changes from latest ship
- cpu bound jobs run with no appreciable
degradation compared to conventional 6152's (each
processor has 2, 4, or 8 meg of private memory).
Processors MAY have different memory sizes.
- I/O bound jobs compete for the same resources
such as disk and are degraded, though total I/O thruput
is higher. A model 80 helps as the 286 cpu becomes a
- kernel compile that took 53 minutes with 1
cpu, took 30 minutes with 2 and 30 minutes with 3. It
appeared to be disk bound with 3 cpu's.
- sharing of work between processors was done at a
high-level with a tool "mc" that one specifies as the C
compiler to make (e.g.: make "CC=mc cc" )
- my setup is to use X11 window manager and have a
window for each secondary cpu.
- many X benchmarks give almost 2x performance
when the benchmark and server run on different cpu's.
DOS implementation details
- one copy of
unix.exe runs, with various structures changed to have
one-per-cpu. Implements a Hot-key (to switch the
keyboard, screens, mouse, and speaker from one CPU to
requests are no-ops from any cpu but cpu 0.
- code provided to
allow secondary cpu's to be automatically started from
primary cpu as part of normal boot sequence.
- "main loop" looks for requests from both cpu's;
generally services each in turn.
- about 1 week's effort to get first version
working; about 1 month's effort after that to fix bugs
and add necessary features.
- code is in
- runs on DOS 3.3
and has been run (once) on DOS 4.0
OS/2 implementation details
- one instance of unix.exe runs per cpu; runs in
own full-screen session
- uses standard OS/2 hot-key to switch between
cpu's and other OS/2
- runs on OS/2 1.1 (PM) and 1.0 (disk
performance much better with 1.1)
- microchannel driver implemented using OS/2
shared memory segment.
- disk performance is good, network performance
and "microchannel driver" performance needs work (about
10x slower than DOS version).
- needs additional work to be "proper" OS/2
program (totally event driven), currently uses polling
for requests from RISC processor that would best be
event-driven threads. This would help performance and
reduce the drag on background tasks.
- second cpu is very handy for kernel develepment
and performance measurements as one can be working on
code on the main cpu and running tests or debugging on
the other cpu. I've found it nice to be able to recover
from installing a kernel with a fatal bug from home
without having someone on site.
Instructions on how to build a
- assumes that you
already have a 6152 with one cpu
- obtain an
aditional cpu (possibly by removing it from another
- install the
December release of 6152 system (or at least the kernel,
boot, and unix.exe from December), you will also need
the December /usr/bin/X11/Xibm as it knows how to save
the screen on hot-key events.
- install the new
@8ff7.adf file onto the reference disk working copy
(e.g. via doswrite -va @8ff7.adf):
AdapterName "RISC coprocessor card"
NamedItem Prompt "I/O port"
"Default I/O address is 1e0. <Disabled> disables
- install additional processor card, and use the
reference diskette to autoconfigure the system. If the
two processors have different amounts of memory the
first one (port 0x1e0) should have the larger amount of
memory, as that is where one usually runs the X server.
- the simplest installation will have two
processors, each with an HD for its own use (you will
need a root and a swap for each processor, but /usr can
be shared, either via mounting it read-only, or via
simplicity I will assume that each disk has the normal
root, swap, and /usr partitions.
- create two new host names, e.g. if the original
system was 'frodo' then create frodo-mc0, and frodo-mc1.
frodo-mc0 will be the gateway machine for cpu1 to the
rest of the world. (You should use your local naming
conventions if they are different from what we use).
- the hd1 disk can
be created by cloning the hd0 disk, e.g. use fdisk and
minidisk to create the DOS/BIOS partition and the unix
partitions respectively and then copy the unix
partitions via the normal newfs/dump/restore mechanism.
0f - / | restore rvf -
0f - /usr | restore rvf -
/etc/rc.config on hd1 to reflect the new hostname and
network address, e.g. change network and hostname
- on the hd0 disk,
add the following lines to rc.config, so that we make
frodo into a gateway (this may require allocating a new
network number for 'frodo')
- now you can boot
up the system. Note that when unix.exe starts it will
tell you that you have 2 processors. The first processor
should now be able to come up normally. Once it gets to
the login state you can hot-key to the second processor
(control-alt-esc), and boot it. It should come up on the
second disk by default (e.g. boot hd(1,0)vmunix.)
- if everything has
worked properly you can add a line to /etc/rc.config so
that the second cpu is automatically started when the
first is about to go multiuser. This is done by
- if one wants to
reboot the second cpu, one can do so by first halting or
rebooting it (e.g. /etc/halt or /etc/reboot), and then
issing the following commands (on cpu 0):
(note that you must put the 6152 version of boot into
/boot rather than the RT version).
- note that
messages about the state of the second cpu are displayed
on the console of the master cpu so that one can
determine that has halted or attempted to reboot.
- note that if your
configuration file doesn't have the line device mc0 at
iocc0 csr 0xffffffff priority 13 then it will need
to be added in order to send packets between the two
9595 Main Page
The above views are my own, not those of my employer.
Bill Webb (IBM AWD Palo Alto), (415) 855-4457.