NetBSD 9.2 and a lot more will now work on Alpha EV6 using a newly
discovered PCI bus cohere protocol involving a couple of SRM commands
and reboots to accomplish whenever the contents of the card cage has
been physically modified.
Here's what I've found:
The Tsunami's bus is reconciled with the PCI bus via a bitsieve, a
matrix stored in undocumented non-volatile memory somewhere on the
board, Pchip most likely.
Triggering a bus-scan with PFREFETCH_MODE enabled just spams the PCI
bus with speculative reads and never gives the cards a voice.
Nothing good is generated and that nothing good is stored in pchip.
This is familiar behavior for the past 30-ish years.
After PREFETCH has been disabled, an attempted boot of the target
operating system, NetBSD 9.2 fails in the expected way, with a Black
Screen of Death at the moment WSCONS is robbed of the framebuffer for
Xwindows. This is the only netBSD problem and it can be resolve with a
simple workaround which separates those two events by some time,
however brief ( a second would do, a tenth ).
The kernel parament 'n', passed via the boot -if n dqa0 command in the
SRM puts Netbsd in a mode convenient to us, as the framebuffer is
initialized as-such (see how nice the text is!) and has had time to
settle. When we take the defaults and 'exit', the process completes to
an XDM login and a desktop. I believe DEC intended this to allow NT
boots under odd circumstances and did not delete the feature, leaving
us a backdoor to boot our operating systems with the machines full
cooperation.
I believe (without testing the method with other than the video card
very thoroughly) that other cards may be positively affected by this
new-found ability to cohere the bus: Sata/Pata cards (Please God!), and
other commodity cards which otherwise would not work.
Why do SCSI cards always work no matter what? The reason is that these
premium cards already know themselves quite well and operate at a
higher-level on the bus. They are immune from the storm coming through
the broken bitsieve, basically establishing a fixed mode without
negotiating?
The Promise ATA133, for example, ought to work, but it is shouted-down
by the mess through the wrong sieve and craps out to pio mode 4. I
think, and I will test, that cohering the machine after installing this
card may give me a fast and reliable (Cheap) local storage.
Why doesn't the onboard ata controller ever really work? It is not
really on the PCI bus, but is rather sort of in-between the Tsunami and
PCI on an ISA bridge and so cannot benefit by a probe. I believe the
drivers for NT, VMS, and TRU use specific driver tweaks to accomplish
stable performance at UDMA speeds on this commodity chip.
The alterations to fix the boot process are trivial, it isn't and never
really has been a NetBSD problem, nor OpenBSD.
Go ahead and cohere your Alpha's bus by:
Install NetBSD 9.2 with the full installation, enable XDM if you want.
It won't run X. We knew that, but the process allows the bus to be
probed without prefetch confusing everthing.
Enter SRM.
Alphabox>>> set pci_parity off
Alphabox>>> set prefetch_mode off
Alphabox>>> init
let the boot proceed to the familiar Black Screen of Death.
Reset the machine and re-enter the SRM
Alphabox>>> set prefetch_mode on
Alphabox>>> init
The machine is permanently configured with the new bitsieve generated
by the probe we just conducted. You will not need to modify these
again unless you makes some hardware change in the card-cage.
If you have an Ev6 in the closet, now's the time to drag it out and
reclaim its glory. This fix allows prefetch to work the way it was
designed to, with tremendous performance benefits, and with the proper
sieve in place, strange things will no longer occur.
I have not tested as yet, but I believe that with this cohere in place
on your macine, and using a similar mechanism to allow the video card
time to settle, OpenBSD 5.9 and/or 6.0 should run, even though no one
ever saw X on them before, you can today.
Why did the oldest versions of NetBSD, OpenBSD, and Linux work in
Xwindows just fine? I am guessing, but given that DEC had no possible
interest in helping anyone do this (Evidence all of HISTORY), these
three teams had no real choice but to slavishly emulate the boot
process in every way they could, not knowing which emulated
eccentricity was the actual key. It worked, but no one outside of DEC
could know why.
When the Openbsd/Netbsd/freebsd teams got new members, changed tools,
rebuilt anew, at some point they forgot why the code was so strange and
obviously inefficient. It should have been a clue, but they instead
'streamlined and optimized'-away the CAREFUL TIMING and they wiped away
another thing that I think was probably once done by Tru, NT, VMS,
OBSD, FBSD, and NBSD, all. I think they blindly passed something to
Pchip, a key bitsieve or a special command to probe without prefetch
and then go back as we are doing manually via SRM. Whatever the
mechanism was, it was not seen as such and removed, breaking X then.
Regression would show what worked, but it would never tell you why
without a terrific forensic effort involving long and unfettered access
to the actual, known-good vintage iron.
Best Regards,
Technoid Mutant
(Also Known as The Technoid and as Technoid6502)
I was unable to connect with this web site today, just curious if it's down
permanently or temporarily. When I visit the site without the SSL (
http://old-computers.com) I am taken to an "Site en construction" page.
Bill
I wanted to share some results I got when attempting to read 800 bli NRZI
9-track tapes:
I have not been able to read any of the 800 NRZi Tapes. I tried a number
of things using four computers. My analysis is detailed below.
The 800 bpi-related calibration on the M4 drive on hand may be off. Just
a guess.
Sources
https://web.geo.uib.no/eworkshop/uploads/Main/123477_23_9914_User_Diagnosti…
Followed suggestions from web search and AI prompts where applicable
There is a set of programs embedded on an eProm on the M4 drive. Program
41 sets the data encoding circuits to handle 800 bpi. I activated
this program before attempting a read. When I put in a 800 NRZI tape into
the drive it analyzes the tape and reports the tape type to be 800 bpi, but
I thought maybe running program 41 to explicitly force 800 bpi mode would
be useful/necessary just in case.
As a general rule, I always reset the drive using these commands before
trying another read:
mt -f /dev/nst0 status - OK (reports 800 NRZ ONLINE)
mt -f /dev/nst0 rewind - OK (rewinds tape)
2. I started with an Ubuntu 18 system. I was successfully able to attach
the drive, etc.
Next I broke down the testing - the simple stuff:
mt -f /dev/nst0 status - OK (reports 800 NRZ ONLINE)
mt -f /dev/nst0 rewind - OK (rewinds tape)
mt -f /dev/nst0 offline - OK (takes the drive offline)
mt -f /dev/nst0 setblk 0 - OK (sets to variable block mode)
mt -f /dev/nst0 fsf 1 - NOT OK (never finds a start of file, runs through
entire tape.)
But when I try to actually read a tape I get errors
Here are examples of the tape read commands, there are many variations one
can try:
dd if=/dev/nst0 of=block1.bin
dd if=dev/nst0 of /dev/null bs=1024
etc
I would open a 2nd window and run the following command to view the system
messages while the dd program is running
dmesg | tail -50
result example:
[ 1802.404408] st0: Failed to read 1326 byte block with 1024 byte transfer.
[ 1813.881884] st0: Failed to read 3846 byte block with 1024 byte transfer
The drive can see data on tape and start reading it but the host computer
is applying the wrong transfer size assumptions. I think.
I don't think setblk 0 is being implemented (use variable block size), but I
don't think this is a fixed-block vs variable block issue. I think that
Linux' st driver is issuing fixed-size read internally and failing when the
drive returns a different record size than expected. There is no
indication that I have bad media or can't read tape or nrz failure at
least. No errors like that.
It appeared to me that the Ubuntu 18 linux version of the st driver cannot
properly stream variable-block 800 bpi tapes, but it's not a SCSI issue.
3. I then built an older style Pentium III with Debian linux (version 7)
with an Adaptec 2950 SCSI controller. The hope was that I'd be closer to a
system that has native ability to read 800 bpi tapes. I used an older
version of linux etc. all to try to avoid emulation issues.
I ran the same tests as above plus other tests, nothing worked.
raw streaming:
mt -f /dev/nst0 setblk 0
dd if=/dev/nst0 of=tape_dump.bin bs=256k conv=noerror,sync
mt -f /dev/nst0 of=dump.bin bs-32k conv=noerror, sync
if tapes are structured then the following would work, but it does not:
mt -f /dev/nst0 fsf 1
dd if=/dev/nst0 of=record1.bin
(and repeat per record )
Result - The fsf command runs and rolls the entire tape, never finds a file
marker to indicate beginning of file. This indicates variable-block,
filemark-less (or nonstandard filemark) 9-track dump tapes, like you find
in IBM systems.
To just avoid buffer failures and bad records and keep going to the end of
the tape I tried this:
dd if=/dev/nst0 of=tape_dump.bin bs=64k conv=noerror,sync iflag=fullblock
Result - it tried endlessly but never advanced the tape.
I also tried cat, which is probably not as good as mt, but worth a shot:
cat /dev/nst0 > dump.bin
also tried
dd if=/dev/nst0 of=tape_dump.bin bs=256k conv=noerror,sync status=progress
repeats endlessly showing the output to the screen...
*Conclusions*
The drive is not successfully completing a forward-read operation. I
observed no forward motion, repeated zero-length reads.
*So I think the situation is ...*
SCSI is OK - I can issue commands that do not involve reading. The tape
transport (the physical movement of tape) is ok, NRZ 800 bpi selection
seems to work, and the mechanism appears to be able to at least detect that
there are blocks of data that can be read.
What does not work is when we attempt to perform sequential streaming
through variable block tapes like the NRZ's I have. The tapes appear
to be non-filemarked,
variable-block 9-track tape where forward streaming is error-sensitive. It
could be that the M4 9914’s NRZ (800 BPI) read path is marginal or out of
calibration. I believe the M4 mechanics for 800 dpi tapes are separate
from the 1600 dpi.
4. DEC 3000 and DEC 4000 servers with native centronics SCSI ports
Unfortunately neither even detected the M4 drive so I was not able to test
further. I asked AI and it suggested that the DEC firmware sometimes had
trouble with older SCSI-1 devices like the M4. Interesting that the PCs
with SCSI card were better able to detect the drive, but they were.
Note that I played around with termination of the SCSI ports to see if
there was a difference, none detected. I opened the M4 rear panel to see
if I could change the SCSI ID number to try a different number to avoid
possible conflicts but there was nothing available. The drive number
appears to be set by the eProm, but I did not want to open up the entire
drive.
The Adaptec controller reports the M4 to be:
Vendor: M4 DATA
Product: OPEN REEL TAPE
Revision: 138P
---------------------------
I am not sure bypassing SCSI and using the Pertec interface would work, I
don't have a computer that uses Pertec for data like that, or I'd have to
figure it out from scratch.
Bill
Hi all,
Around 1981, Intel made a 8086 companion chip named _operating system
processor_ (i80130, and i80150, resp.) which comprised a ROM and some
interrupt logic. The 80130 contained sort of a BIOS for iRMX86, the
80150 supported CP/M-86. Few info can be found at
https://en.wikipedia.org/wiki/Intel_80130, and a datasheet exists at
alldatasheet.com.
Some lore is also found in some history pages, but not much more than
the datasheet contains.
Was the ROM content of both chips dumped and is available on the
Internet somewhere, or does someone have such a system (supposedly some
iAPX86/30) and is willing to make this public, e.g. upload to bitsavers?
THX to any pointers
Kind Regards
Holger
