<div dir="ltr"><div dir="ltr">On Mon, 17 Jul 2023 at 20:49, Noel Chiappa <<a href="mailto:jnc@mercury.lcs.mit.edu">jnc@mercury.lcs.mit.edu</a>> wrote:</div><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"> > From: Henry Bent<br>
<br>
> there will be a lengthy addendum shortly.<br>
<br>
The most useful thing is probably this:<br>
<br>
<a href="https://minnie.tuhs.org/cgi-bin/utree.pl?file=V4/nsys/ken/low.s" rel="noreferrer" target="_blank">https://minnie.tuhs.org/cgi-bin/utree.pl?file=V4/nsys/ken/low.s</a><br>
<br>
which lists exactly what was there; not only the types, but how many of each<br>
there are. This is from 'nsys', which is slightly before the actual V4, so<br>
it's quite early. 'low.s' is inherently machine-specific; i.e. different<br>
machines would share most kernel files identically, but _not_ this one -<br>
unless they had _absolutely identical_ device sets. So this one is _probably_<br>
the one from the /45 in picture.<br>
<br>
It shows:<br>
<br>
RK11<br>
RF11<br>
PC11<br>
TC11<br>
TM11<br>
<br>
1xKL11<br>
12xDC11<br>
1xDP11 (synchronous serial)<br>
1xDN11 (dial-out asynch control)<br>
<br>
1xDR11C (parallel port to -11/20)<br>
2xDC11 (Screw Works voice synthesizer)<br>
1xDR11A (voice response unit)<br>
1xDR11C (C/A/T typesetter)<br>
<br>
(Line printer, card reader and RP11 are commented out; more about the RP11<br>
in a later message.<br>
<br>
<br>
There's also this:<br>
<br>
<a href="https://minnie.tuhs.org/cgi-bin/utree.pl?file=V4/nsys/ken/11-45" rel="noreferrer" target="_blank">https://minnie.tuhs.org/cgi-bin/utree.pl?file=V4/nsys/ken/11-45</a><br>
<br>
which is a bit hard to interpret, but I think might list what's in each rack:<br>
the TC11, RK11 (early ones), RF11 and TM11 (early ones) were large custom<br>
wire-wrapped backplanes which bolted into the front or back of a 19 inch<br>
rack; this:<br>
<br>
<a href="https://gunkies.org/wiki/RK11-C_disk_controller" rel="noreferrer" target="_blank">https://gunkies.org/wiki/RK11-C_disk_controller</a><br>
<br>
has an image of such an RK11. The "MOS 16-24" is probably a reference to an<br>
MS11:<br>
<br>
<a href="https://gunkies.org/wiki/MS11_Semiconductor_Memory_System" rel="noreferrer" target="_blank">https://gunkies.org/wiki/MS11_Semiconductor_Memory_System</a> <br>
<br>
which had to mount in the CPU backplane. The "MM" entries are likely core<br>
memory units; probably MM11-K's:<br>
<br>
<a href="https://gunkies.org/wiki/MM11-K_core_memory" rel="noreferrer" target="_blank">https://gunkies.org/wiki/MM11-K_core_memory</a><br>
<br>
since they seem to be 4KW each. (Maybe MM11-E's or 'F's, though; those are<br>
also 4KW each.) I'm not sure what they "PL"s are - probably Plessey core?<br>
Anyway,it looks like the machine had 104KB total.<br>
<br>
<br>
This file:<br>
<br>
<a href="https://minnie.tuhs.org/cgi-bin/utree.pl?file=V4/nsys/ken/conf.c" rel="noreferrer" target="_blank">https://minnie.tuhs.org/cgi-bin/utree.pl?file=V4/nsys/ken/conf.c</a><br>
<br>
lists all the types of devices on the machine. One oddity is that it lists<br>
two RK11's; but if you look at the RK11 driver:<br>
<br>
<a href="https://minnie.tuhs.org/cgi-bin/utree.pl?file=V4/nsys/dmr/rk.c" rel="noreferrer" target="_blank">https://minnie.tuhs.org/cgi-bin/utree.pl?file=V4/nsys/dmr/rk.c</a><br>
<br>
it's only set up to handle one physical controller. But there is this:<br>
<br>
#define JRK 1 /* temp */<br>
<br>
if (bp->b_dev.d_major==JRK)<br>
d = bp->b_dev.d_minor;<br>
else<br>
d = bp->b_blkno%3;<br>
<br>
so the two different major device entries appear to handle the same disks in<br>
different ways ("d = bp->b_blkno%3" will spread a virtual drive across three<br>
physical drives).<br>
<br>
<br>
Memory, it would have been hard to say (UNIX even then sized memory at start<br>
up) but then I found that '11-45' file. I also found a copy of the CACM<br>
version of the UNIX paper:<br>
<br>
<a href="https://people.eecs.berkeley.edu/~brewer/cs262/unix.pdf" rel="noreferrer" target="_blank">https://people.eecs.berkeley.edu/~brewer/cs262/unix.pdf</a><br>
<br>
which says the machine had 144KB (so they had added 40KB more at that point).<br>
(I seem to recall someone had scanned the SOSP version; I didn't save the<br>
pointer, but if someone knows where it is, it would be interesting to look,<br>
and see what it says - they seemed to update this paper on a regular basis -<br>
the copy included with V6 talks about the -11/70.)<br>
<br>
The system at that point had "a 1M byte fixed-head disk .. four moving-head<br>
disk drives which each provide 2.5M bytes on removable disk cartridges, and<br>
a single moving-head disk drive which uses removable 40M byte disk packs"<br>
<br>
The RS11 disks for the RF11 were 512KB, so either they'd added a second one,<br>
or switched to an RS04 (but that's a MASSBUS device). The big disk was an<br>
RP03 so they had added an RP11, which wasn't present earlier.<br>
<br>
Noel<br></blockquote><div><br></div><div>Noel,</div><div>Thank you very much for this thoroughly researched and documented explanation. I hope that it will be of use to others as well.</div><div><br></div><div>-Henry <br></div></div></div>