Dear Antonio,
   
   Thank you very much for enlightening me! I'm sure that port-vax hackers
are reading our discussions with great interest too. However, this
discussion has been taking place in several different and unrelated
threads, and so I'm consolidating them into one and changing the subject
appropriately.
   You wrote:
> Flicking the switch on a VAXstation 3100 Model 38 informs the console
> that you wish to run without the graphics console - it does not turn the
> VAXstation into a MicroVAX. If you do this on a system running VMS I
> *believe* it will refer to the config as a VAXserver of some sort, but it
> was never supported (AFAIK).
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^
   Actually it was, as far as I can see. The VS3100 M40 owner's manual says
that a high-end VS3100 can be run permanently with the alternate console if
it is used only as a server for smaller machines and no longer has a
monitor. Since it doesn't say anything about the OS, I'm assuming that this
was OKed for both VMS and Ultrix.
   So far I have gathered the following from your explanations:
   1. The MicroVAX vs. VAXserver distinction in KA650 and KA41 is a bit in
the EPROM.
   2. VAXstation 3 used KA650-BA and NOT KA650-AA.
   3. Converting a VAXstation to the serial console makes it appear to the
software as a VAXserver, rather than a MicroVAX.
   So far I have been assuming that VAXstations are being viewed as
drastically different from both MicroVAXen and VAXservers, which are also
different from each other, but not as much. Also I was assuming that
MicroVAXen are more "mainstream" than VAXservers. However, points 2 and 3
contradict these assumptions, especially the latter one. Is it more correct
that MicroVAXen kind of stand apart while VAXstations and VAXservers are
closer together?
   You wrote:
> The jumper is not there for licencing purposes.
> It is there so the console knows whether it is supposed to behave as a
                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> workstation or as a microvax; the fact that the OS gets to know is
  ^^^^^^^^^^^
> incidental.
   Now we are getting to the heart of the matter. What IS the difference
between "a workstation" and "a microvax"? People were suggesting to me that
it's licensing. You are saying that it isn't. It isn't the console, is it?
The console is determined by pins 8 and 9 on the DB9 and not by the jumper
(there are a lot of people who change the console without even knowing
about the jumper). WHAT IS IT then?
   You wrote:
> I'm guessing that the console doesn't initialise the video, so there is
> not much point telling you it is there.
   Today (20-JAN-1998) I have performed the following experiment on one of
my KA42-Bs. I ran the exact same box with the console switch both up and
down, connecting a terminal or a monitor and a keyboard appropriately. In
both cases the self-test sequence and the configuration display (TEST 50)
showed both the base mono video and the 8PLN video board as present.
Therefore, at least on KA42 not initializing the video if it isn't used is
not the issue. I haven't done this experiment on my KA410s yet, will
probably get to that tomorrow.
   You wrote:
> The MicroVAX 3100s (KA41 series) do not have video circuitry so there is
> no question of converting a KA41 to a KA42 or vice-versa.
   What I'm really wondering about is whether such circuitry exists in the
first place or is it just a software construct. Take KA410 for instance. By
now I have learned that it has never had any components omitted. However,
imagine hypothetically that you wanted to make a MicroVAX-only version of
it. Is there some actual circuitry that's JUST for the video and could be
hypothetically removed? Or is the frame buffer taken out of main memory and
whatever chip produces the video signal also does some vital functions like
DRAM refresh?
   There is one more twist to this hypothetical issue. Imagine there were a
version of, say, KA410 without base mono video. Then maybe it would be
possible to make that beast use a graphical console by adding a GPX or SPX
video board. Assuming the DB15 connector and the circuits leading to it
were left in place, the added board would be able to send its video output
to the monitor, right? Keyboard and mouse would work, since they are purely
software constructs made out of fully generic serial ports, right? If these
arguments are correct, they lead to an important observation that the real
meaning of KA41 not supporting video is not that it doesn't have base mono
video but that it can't have any video at all. Suppose that I were to stick
a GPX or SPX board in a KA41 system. It should be mechanically possible,
since on KA410 video boards and communication options are inserted into the
same connector, and KA41 should take the same communication options as
KA410. So KA41 should be mechanically compatible with GPX and SPX boards,
but it's a completely different story that they wouldn't work because of
the lack of the DB15 connector. If the arguments above are correct, this is
the real meaning of KA41 not supporting video. Are they?
   (Continuing writing this on 21-DEC-1998.) Today I have continued the
experiment with KA410s. I have several boxes, both MicroVAXen and
VAXstations, and I tried connecting each both to a VT220 and to a mono
monitor (none of the boxes has a GPX board). First I tried two VS2000s.
Guess what, each of them was saying that the mono video is present
regardless of which console I was using! I wasn't doing anything with the
jumper, though, since I don't know which one it is. Also note that the ID
displayed didn't depend on the console used either. One box was always
saying "KA410-A V1.2" and the other was always saying "KA410-B V2.1". The
first box seems to be pretty old, and the "A" looks strange given that it
clearly says "VAXstation 2000" on the front. I'm probably not the first
hacker who has laid his hands on those boxes, though, so it's possible that
someone has messed with the jumpers. But the real surprise came with the
next experiment. I tried it on one of the MV2000s that Richard has brought
me last week, and guess what, it didn't work with the graphical console at
all! When connected to the VT220, it identified itself as "KA410-A V2.3"
and showed the mono video as absent ("F_.."). Note though that when I was
trying it with the monitor the latter did react to the machine turning on.
If the monitor is connected to the machine and turned on, but the machine
is off, one can see a characteristic white rectangle in the center of the
screen. The rest of the screen stays completely black even at the maximum
brightness, which indicates that the cathode ray scans only that rectangle.
When I turned on the MicroVAX with this monitor connected to it, the
rectangle "unwrapped", so the cathode ray now seemed to be scanning the
screen correctly, but setting the controls back to normal revealed that it
was all black. The keyboard was clicking on keypresses, so it was getting
power, but pressing Lock didn't cause the Lock LED (or any other LED for
that matter) to light, so the MicroVAX wasn't interacting with the
VAXstation-style keyboard. This means that either MicroVAX and VAXstation
system boards do differ after all or I needed to do something with the
jumpers.
   You wrote:
> The VAXstation 3100-30/38/76 all used the 68-way connector (at least I
> think its 68-way ... I didn't actually count it!).
   and
> The VAXstation 3100-30 and -38 both use a daughter board which provides a
> SCSI interface and a floppy disk interface (there are at least two
> variants of this board).
   That's right. The two variants that I know of are SCSI/SCSI and
SCSI/MFM. The external SCSI connector has 68 contacts (I did count :-)).
It's a high-density one that looks deceptively close to SCSI-3 (wide SCSI),
but it has a reversed gender and quite possibly a non-standard pinout. Plus
the underlying SCSI interface is far from SCSI-3, it's narrow single-ended
SCSI-1. (I'm not saying that it's bad, though. I actually like it best.)
It's easy to tell if a system uses this daughterboard design. This
daughterboard sits in the upper-left corner of the system unit if viewed
from the back, it has this funny external connector, and the latter is
covered by a very characteristic cover. These characteristics of the
external connector almost certainly guarantee that the daughterboard design
is used. It is possible in theory to make the external connector look right
and be in the right place while keeping the SCSI chips on the system board,
but it's far from easy and I'm sure no one would do that. In this case the
external connector would have to be crimped on a ribbon cable. The
connector is a high-density one, so the ribbon cable would have to be high-
density too, which causes other problems. The connector would have to be
mounted in the opening, but the enclosure provides no mounting elements in
that opening, since it was designed for a connector that sticks out from a
PCB. In short, the absence of the daughterboard design would be immediately
apparent externally.
   In the quote above you are saying that this daughterboard design is used
in M30 and M38. I have to include M40 and M48 too. In the manual for VS3100
M40 the back of the system unit is drawn very well, and I clearly see that
the external connectors looks just like the one I'm used to seeing on my
M38s, and is located in the right place under the right type of cover. Plus
you were assuring me yourself that M40 uses exactly the same system board
as M30 and M48 uses exactly the same system board as M38. Well, the same
system board implies the same daughterboards accepted, right?
   You wrote:
> The VAXstation 3100-76 has its SCSI interfaces on the main board.
   Immediately upon reading this I put my coat on and took a walk to the
next building where there is an M76. It isn't mine, so I can't open it up
and see it directly, but the back panel suggests the SCSI daughterboard is
there, since it looks EXACTLY like that of my M38s (you can't tell which
machine it is without looking at the front).
   You wrote:
> I don't remember what the various DECstations did. I think the DECstation
> 3100/2100 used the same box as the VAXstation 3100-30/38 so they would
> have had the same SCSI connector, but the interface was probably built in
> to the motherboard (via the SII, IIRC).
   On my way back to my office after checking the VS3100 M76 I stopped by
yet another building where there is a DS3100 (again, not mine). And again
it looked exactly the same as VS3100 M38 and M76. As I have explained
above, it's unlikely that the SCSI chips are on the system board if the
connector is up there in an extremely inconvenient location. By the way,
what's the difference between DS2100 and DS3100?
   As for the sii, that's just the name that Ultrix uses for the NCR 5380
SCSI interface. 5380 is used in systems based on KA410, KA41, KA42, KA43,
and KN01 (at least), either directly on the board or on a daughterboard.
And by the way, Ultrix uses the name "sii" on VAXen too, not just on
PMAXen. Only NetBSD/vax is an exception in that it calls it "ncr".
Apparently Bertram doesn't consider DECishness important :-). Even
NetBSD/pmax calls it "sii", I think.
   You wrote:
> The MicroVAX 3100 series used the 50-way Amphenol connector (at least as
> far as the MicroVAX 3100-90 ... I don't know about the 3100-88 or 3100-98
> where the box changed completely).
   and
> The MicroVAXes all (AFAIK) have the SCSI interface on the main board.
   I'm pretty sure that there was a significant change in this area between
KA41-based ones and M30+. As you say yourself, the former use NCR 5380.
This means SCSI-1. I'm pretty sure that the latter use NCR 53C94, which is
SCSI-2. For M90 that I know for sure, since I have read it in an excerpt
from some DEC publication that Jim Agnew has put in his FAQ. I'm pretty
sure that this is also true down to M30/40. Although I have never seen an
M30+, I know (will explain later) that its SCSI connector is SCSI-2 (50-
contact high-density), which is quite small and fits in line with serial
and Ethernet ports.
   I doubt that KA41-based boxes have SCSI-2 external connectors, since
they are SCSI-1 after all. Plus Thordur says that on his box it's
Centronics-50 (the standard connector for SCSI-1). You are referring to
Amphenol, but I don't quite know what it is. Is it the SCSI-1 one
(Centronics-like) or the SCSI-2 one? If it's Centronics-50, I doubt that
it's in line with serial and ethernet ports, since it's too big for that.
Plus Thordur indicates that it's above this line. What I'm assuming is that
the system board has only internal SCSI connectors, and a ribbon cable runs
up from one of them to an upper opening where it ends with a Centronics-50
connector crimped on it. Is this the case?
   You have convinced me that KA41 is not KA42, especially if my above
theory about Centronics-50 turns out to be correct. If it is correct, it
completes the picture of a perfect external match between MicroVAX 2000 and
MicroVAX 3100. They match in serial ports, communication options, the
location of the SCSI chips, nicknames, and, as it turns out now, the
external SCSI connectors. By the way, do you remember that in the SHOW DEV
output that Thordur has once posted the host adapter's SCSI ID was 7 and
not 6 on both SCSI buses? 7 is the standard in SCSI in general, but both
KA42 (VS3100) and KN01 (DS2100/3100) use 6 (at least by default, I don't
know if it's changeable). Is this yet another difference between KA41 and
KA42?
   Now I also see that there was a re-design involved. Originally I have
thought that even if KA41 and KA42 are different, they were still designed
at the same time by the same people. Now it seems to me that KA42 is the
original mainstream version and KA41 is a side branch. Their ideologies are
completely different, so it's clear that they were designed by people with
completely different ideological views, and the ideology of KA42 is much
more in line with the rest of DEC stuff, which suggests that KA41 is a side
branch and not vice-versa.
   You wrote:
> The designs are clearly related, but they are not the same board, they
> were even quoted as having slightly different performance (3.5VUPs for
> the KA41-E and 3.8VUPs for the KA42-B).
   Note that KA42-B's performance of 3.8 VUPs equals that of KA655, and
KA42-A's performance of 2.8 VUPs equals that of KA650. KA650 has a 64 KB
cache, so I'm assuming that KA655, KA42-A, and KA42-B do too. KA41-A/B's
performance of 2.4 VUPs, on the other hand, matches that of KA640, which is
like KA650 but has 4 MB of RAM and the DSSI interface on-board. I guess
that KA640 is a bit slower than KA650 because when squeezing in the RAM and
the DSSI interface the designers had to take something out, and they
decided to take out the 64 KB cache. It is plausible that the same was
necessary when squeezing in the NCR 5380 chips and the supporting logic to
go from KA42 to KA41.
   As for MV3100 M30+ and VS4000, it seems to me that the system boards of
different models, however different, should be plug-compatible. First, I
believe that DEC allowed all M30+ models to be in-cabinet upgraded to
higher models of the line. Second, I have the July 1997 issue of _Digital
Age_ in front of me, and on its back cover their is an ad for a THIRD-PARTY
VAX (yes, such things exist!). Nemonix advertises a 65 VUPs VAX system
board that can be, according to the ad, swapped into MV3100 M30 through
M9x, VAX 4000 model 10x, and VS4000 M60 and M9x. Since the ad doesn't say
anything about this, I'm assuming that a VS4000 will remain a VAXstation
after this conversion. Well, if the same system board can be plugged into
all of these systems, their native system boards have to be plug-
compatible! And if conversions don't change the graphics status, the
graphics hardware has to be on a daughterboard.
   As for SCSI, a DEC paper says that KA50 (MV3100 M90) and KA52 (VAX 4000
model 100) use NCR 53C94 (the SCSI-2 chip), as I have expected. I think
that this goes all the way back to M30/40. Since the boards are plug-
compatible, they have to have the same the same external connectors if they
are on the system board. I haven't seen any of these DEC-native boards, and
the picture of the Nemonix board in the ad isn't very detailed, but there
is a connector that looks like SCSI-2 (the high-density one).
   And I'm still curious about the KA630 and KA650 console thing.
   
   Sincerely,
   Michael Sokolov
   Phone: 440-449-0299
   ARPA Internet SMTP mail: sokolov@alpha.ces.cwru.edu