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Resurrecting a Bull DPX/20 200 workstation

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Christian Holzapfel

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Nov 1, 2021, 3:32:41 PM11/1/21
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Hi guys, it's nice to see you're all still in down here! I've been away for a long time, just until yesterday when MCA fever hit me again and I acquired a Bull DPX/20 200 workstation, which seems to be an OEM manufactured IBM 7006 (-41x?). At least the case and mainboard are the same.
Unfortunately the box is pretty stripped: no HDD, no CD-ROM, no drive cages, but a floppy drive, a POWER Gt4xi graphics adapter with the evil 3W3 connector and... no RAM!
The seller gave me 8 pieces of Kingston KTM-9595/32 which he believes to come from "some RS/6000", but the 7006 keeps yelling some

c01 100 200 300 411
c02 100 200 300 412
c03 100 200 300 413
c04 100 200 300 414

codes at me, which I translate to "bad RAM in slots A, B, C, D" using the 7006 operator guide.

Looking that Kingston RAM up shows it is at least used for the 9595 server. No reference to the RS/6000 though. Some refer to it as parity, others as ECC.

Can anyone tell if this is the right RAM for that system?
If not, which one do I need? FRUs would be really helpful.

Also, if anyone is sitting on a stash of bored drive cages, I could help him out...

Eventually I'd like to restore this beautiful beast to an operational condition. It had been asking so sadly...

Thanks, peace and out,
Christian

WBSTClarke

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Nov 1, 2021, 4:44:23 PM11/1/21
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PS/2s which support ECC SIMMs require 39-bit ECC SIMMs. RS/6000s require 40-bit ECC SIMMs. Kingston KTM-9595/xx are 39-bit and only suitable for PS/2s, but useful for >64MB capacities.

Check Appendix C of this:
<http://ps-2.kev009.com/rs6000/manuals/Diagnostic_Information_for_Micro_Channel_Bus_Systems.PDF>

Christian Holzapfel

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Nov 1, 2021, 4:53:27 PM11/1/21
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Argh, so it's close, but not right.
Thank you for that! I'll get in touch with the seller and have him check on the remaining memory.

Christian Holzapfel

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Nov 1, 2021, 4:53:37 PM11/1/21
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So little remaining memories, so many questions...

I assume, it *could* run my ancient copy of AIX 4.3.3, would happily interact with my PC style Model M, and any SCSI CD-ROM drive would be just fine for the start, right?

And with this video thing... The card is a 11H4913, so it is a "POWER Gt4xi (1-5) 24-bit Graphics Card", according to some awesome know-how site.
Is its companion, the "Processor Card FRU 52G1343 (Placed in Lower Numerical Slot than Graphics Card)" actually required for the operation?
There is an empty MCA slot right next to it, so I assume the processor card missing.
If I recall it right, it's not as simple as dropping in an XGA-2, hmm?

Kevin Bowling

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Nov 1, 2021, 6:14:08 PM11/1/21
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All of the DPX/20 I've seen are the same as the IBM manufactured
systems. The only special machines are Bull Escala where they had some
oddities such as the PowerPC 620 actually ship (!). So yes your AIX
4.3.3 will work and will be a good fit for this system.

It sounds like you have a GT4i, which will run on its own. And 3w3 is
quite forgiving you just need a Sync-on-green monitor.
http://ps-2.kev009.com/sog/

Regards,
Kevin

Wolfgang Gehl

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Nov 1, 2021, 7:15:18 PM11/1/21
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Am 01.11.21 um 21:53 schrieb Christian Holzapfel:
Hi Christian,

as for the memory, your machine needs fast page ram with parity (no
ECC!): https://ardent-tool.com/RS6000/7006/7006-41x.html

The POWER Gt4xi consists of two cards. If one is missing it will most
likely not work. If it does work it's a nice graphics card with true
color support for up to 1280*1024 pixels.
https://ardent-tool.com/RS6000/gt4xi_graphics_display.html
If you want to make use of a POWER Gt4xi your monitor must support sync
on green.
What you probably want to have is a GXT500D. This is just an example:
https://www.ebay.de/itm/283171852255
This one has a 13W3 interface which can be adapted to standard VGA.

I don't know any video card which works with both Power PC and x86 PC.

My 7006 runs AIX 4.3.3 from a 3,5" 9GB hard drive, that sits under the
floppy drive. No drive cage is required. To install AIX on your machine
you need the key to turn the lock in the service position, a SCSI
CD-ROM, a SCSI drive, AIX CDROM media and null modem cable to an other
PC with a telnet client.

If you want to get rid of the Kingston ECC ram I gently raise my finger.

Good luck and good night

Wolfgang

Christian Holzapfel

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Nov 3, 2021, 9:33:37 AM11/3/21
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Hi everyone.
I made the system pass the RAM error codes by installing 4x 8 MB PS/2 parity RAM. It's enough for a first try, but hopfefully not the final setup ;-)

With key in normal mode, the system now hangs on a 223 code (attempting a normal IPL from SCSI attached devices).
What baffles me is that none of my HDDs likes to spin up when connected to the internal 50-pin SCSI port.
I've disabled the external port (due to lack of a proper terminator), tried two different 50-pin cables and two disks.
They all spin up fine without the SCSI connected, so power is there.
Tried some 9.1 GB SCA drive with an adapter, and an IBM DALS-3540 (540 MB, set to ID 3, spin up, termination on).
Is there a special cable required, is the planar toast or am I missing anything else?

With the key in maintainance mode, it hangs on a 262 code (keyboard not detected), although it flashes the Model M's lights.

Any thoughts?

Wolfgang, I'll check if you can have the leftover ECC RAMs. You're welcome to have it, if the seller doesn't want it back. Im on it.

~Christian

Christian Holzapfel

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Nov 3, 2021, 9:43:04 AM11/3/21
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Will the 7006-42W board (finally found a label on it!) boot from an additional MCA SCSI adapter? Which ones are supported on this machine?
I have a spare Future Domain MCS-600/700 / IBM PS/2 SCSI-2 from a 9576 that I will give a try, but that's probably not what it wants, is it?

Christian Holzapfel

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Nov 3, 2021, 11:22:31 AM11/3/21
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Christian Holzapfel schrieb am Mittwoch, 3. November 2021 um 14:43:04 UTC+1:
> Will the 7006-42W board (finally found a label on it!) boot from an additional MCA SCSI adapter? Which ones are supported on this machine?
> I have a spare Future Domain MCS-600/700 / IBM PS/2 SCSI-2 from a 9576 that I will give a try, but that's probably not what it wants, is it?

It's not going further with the FD controller either.

After pulling and checking the NVRAM 3 V battery, the stop code has changed from 223 (attempting a normal mode IPL from SCSI-attached devices specified in NVRAM IPL devices list) to 233 ([..] specified in IPL ROM default device) for obvious reasons, but still no disk spinning up.

Christian Holzapfel

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Nov 3, 2021, 3:36:10 PM11/3/21
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I just measured the SCSI control lines /BSY, /ACK, /RST, /MSG, /SEL, /C/D, /REQ, /I/O, with and without a drive attached.
Turns out, they all stay low at all times, so most likely, the host controller has deceased.
The planar PCB looks clean and intact, no burnt fuses or blown capacitors, so probably not much to win there.

What are my options? Will it take Spock, Corvette, Passplay, Cheetah and friends?
If yes, will I need to look out for any special revisions?

Sad thanks,
~Christian

RickE

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Nov 3, 2021, 5:18:32 PM11/3/21
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On Wednesday, November 3, 2021 at 3:36:10 PM UTC-4, Christian Holzapfel wrote:
> What are my options? Will it take Spock, Corvette, Passplay, Cheetah and friends?

Assuming that the Bull DPX/20 200 is a direct match for an IBM 7006, then it won't work with any of the PS/2 SCSI adapters, it will want one of the RS/6000 SCSI adapters, and it will probably only boot from a 4-1 (FRU 51G9425). This is similar to a Spock, but it has RS/6000 VPD burned into it, and that makes the critical difference. I purged out my RS/6000 microchannel adapters quite a while ago, sorry.

With regards to memory, you'd likely be looking for P/N 74G1020, FRU 73G3235 (Four 32MB modules yielding 128MB RAM), I probably have some of those hiding in the basement somewhere (might take some digging to find them).

Wolfgang Gehl

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Nov 3, 2021, 5:37:15 PM11/3/21
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Am 03.11.21 um 20:36 schrieb Christian Holzapfel:
A last try with the internal SCSI port:

* is the external SCSI port disabled? To do this, set the jumpers
exactly to the other position than on this picture:
http://www.supervinx.com/OnlineMuseum/IBM/42T/005-IMG_2763.JPG.html

* unplug all expansion cards including the graphics card

* set the SCSI ID of the hard disk to 0 (a dim memory tells me that
counting is the other way around than on PS/2 machines), passive
termination enabled, no other SCSI device on the cable

* Boot the system in service mode

Please report back with which display code the system stops.

Repeat the procedure with the SCSI cable disconnected and and again tell
us with which display code the system stops.

Wolfgang


Christian Holzapfel

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Nov 4, 2021, 7:54:24 AM11/4/21
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Wolfgang Gehl schrieb am Mittwoch, 3. November 2021 um 22:37:15 UTC+1:
> Repeat the procedure with the SCSI cable disconnected and and again tell
> us with which display code the system stops.

Thank you Wolfgang, but the issue remains:

With a known-good SCSI drive at ID 0, external SCSI disabled, termination at the HDD on/off, no adapters at all, the system hangs on
262 (keyboard error) in maintainance mode
233 (boot from IPL) in normal mode
with or without the SCSI cable being plugged.
If the SCSI cable is plugged, the disk won't spin up.

While probing the SCSI bus, I didn't even see anything on the control lines - not even a glitch on power-up.


ekb...@vnet.ibm.com schrieb am Mittwoch, 3. November 2021 um 22:18:32 UTC+1:
> Assuming that the Bull DPX/20 200 is a direct match for an IBM 7006, then it won't work with any of the PS/2 SCSI adapters, it will want one of the RS/6000 SCSI adapters, and it will probably only boot from a 4-1 (FRU 51G9425).

Well, at least the Ardent Tool states that the 7006 should happily accept the Corvette in no perticular revision, also for boot:

https://www.ardent-tool.com/IBM_SCSI/SCSI-FW.html#RS6000_Boot_Support

(at least, if you read it in an optimistic way...)

Christian Holzapfel

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Nov 4, 2021, 11:54:25 AM11/4/21
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I took out the planar, and everything looks pretty clean and in-order to me.
All self-resetting fuses F1-3 are ok, no leaked electrolytics or blown tantal caps.
No burnt smell, no smoked traces.
Unfortunately, everything between the SCSI controller NCR 53C720 and the connectors seems to be routed on the inner layers.

Well, there's one thing: One capacitor on the buttom side, C256, seems to have fled off the board.
It looks like it had been there once, but had simply fallen off at some point:

http://www.holzapfel.biz/7006-42W/7006_missing_C256.jpg

However, this is at the opposite corner, far away from the SCSI controller itself and its connectors:

http://www.holzapfel.biz/7006-42W/7006_planar_scsi.jpg

Being connected between a 74ABT240 buffer IC's GND and VCC pins, its job is simply stabilizing the IC's power, not being part of any important oscillator circuit or so.
I simply dropped a standard 100 nF back in there.

While having it open, I replaced one of the electrolytic Cs that I found bad in some other device from the same era (an LPKF 91s PCB mill).

No spinning disks at all.

Wow, this is getting desperate...

Christian Holzapfel

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Nov 4, 2021, 12:52:08 PM11/4/21
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Probing traces shows that all I/O pins of the SCSI connector are directly connected to pins of the NCR 53C720 controller IC on the board. No broken lines, and no (safety) logic in between.
So if anyone might have put in a 50-pin cable the wrong way around, it might have roasted the SCSI controller itself.

Before I dig in deeper into the 53C720's host interface, I'll try to come up with some additional SCSI adapter first.
The 7006-42W feature matrix
https://www.ibm.com/common/ssi/ShowDoc.wss?docURL=/common/ssi/rep_sm/w/877/ENUS7006-42W/index.html
lists some "IBM SCSI-2 Fast/Wide Adapter/A" which is a regular "Corvette", isn't it?
Getting a card today is difficult enough, but getting the proper cable with that naughty mini-Centronics plug, well......

Wolfgang Gehl

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Nov 4, 2021, 2:14:18 PM11/4/21
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Am 04.11.21 um 12:54 schrieb Christian Holzapfel:
Hi Christian,

it seems you're right and the onboard SCSI is not working. My point is
to get past 262 in service mode, just to make sure, the system continues
POST even without a working SCSI subsystem.

Since there is no monitor and no video card you might as well just pull
the keyboard off.

Give your system a boot device and connect the floppy drive. Disconnect
the SCSI cable and tell us what happens.

Wolfgang

PS: I have a spare corvette. If you want it, contact me offline.

Christian Holzapfel

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Nov 4, 2021, 4:11:38 PM11/4/21
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Wolfgang Gehl schrieb am Donnerstag, 4. November 2021 um 19:14:18 UTC+1:
> it seems you're right and the onboard SCSI is not working. My point is
> to get past 262 in service mode, just to make sure, the system continues
> POST even without a working SCSI subsystem.
>
> Since there is no monitor and no video card you might as well just pull
> the keyboard off.
>
> Give your system a boot device and connect the floppy drive. Disconnect
> the SCSI cable and tell us what happens.

With floppy connected, and a random or without a diskette in the drive, with or without keyboard, the system finally hangs at 262 when set to maintainance mode.

This is the full error code list. I had to use my phone's slow motion video recording function to capture the quick ones.
Some look pretty fatal to me, indicating some serious planar failures, if they're not exaggerating:

211 IPL ROM CRC comparison error (irrecoverable)
215 A low voltage condition is present (irrecoverable)
218 RAM POST is looking for good memory
21c L2 cache is not detected (That's ok, there is none on this specific model)
219 RAM POST bit map is being generated
220 IPL control block is being initialized
216 IPL ROM code being uncompressed into memory
290 IOCC POST error (irrecoverable)
288 Adapter card slots being queried
291 Standard I/O POST running
283 Serial port POST executing
272 Tablet Port POST
271 Mouse and Mouse port POST
219 RAM POST bit map is being generated
291 Standard I/O POST running
262 Keyboard not detected as being connected to the system's keyboard port

Wolfgang Gehl

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Nov 5, 2021, 1:23:24 PM11/5/21
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Hi Christian,

a CRC error indicates that the inital program load data stored in ROM is
corrupted.

Am 04.11.21 um 21:11 schrieb Christian Holzapfel:
> 211 IPL ROM CRC comparison error (irrecoverable)

Whether and how such a problem can be solved, I cannot say.
Unfortunately, I don't have a 7006 replacement planar either. That means
I can't help you any further.

Wolfgang

Louis Ohland

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Nov 5, 2021, 2:58:34 PM11/5/21
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Gurp. Get a copy of the correct ROM? Like that is even likely?

Christian Holzapfel

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Nov 5, 2021, 9:16:12 PM11/5/21
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Louis Ohland schrieb am Freitag, 5. November 2021 um 19:58:34 UTC+1:
> Gurp. Get a copy of the correct ROM? Like that is even likely?

It could be worth a try.
Looking at
https://www.ardent-tool.com/RS6000/7006/7006-41x.html
are you referring to U5? This seems to be the EPROM to me.

The label states

P/N 11H5838
E/C D 73041
(c)IBM 5628

Maybe someone has something similar, and a reader, and waaay to much time..?

Louis, if I recall correctly, you bought my 7006-42T some years ago. Are you able to read out a dump?

I'll try to read out mine and identify some checksums or seemingly corrupted areas.

Thank you all for your friendly offers and helpful ideas.

Christian Holzapfel

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Nov 6, 2021, 6:41:17 AM11/6/21
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Christian Holzapfel schrieb am Samstag, 6. November 2021 um 02:16:12 UTC+1:
> I'll try to read out mine and identify some checksums or seemingly corrupted areas.

The chip is an ST Microelectronics 27C4001, 512 KB, UV-erasable EPROM, chip ID 20 41.

This ist the contents of my chip:

http://www.holzapfel.biz/7006-42W/11H5838_crc_error.bin

The readable copyright notice from address 0x100 onwards indicates that it's probably the correct chip type.

Christian Holzapfel

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Nov 7, 2021, 12:06:46 PM11/7/21
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The IPL ROM image can be disassembled and decompiled with Ghidra without any troubles - at least Ghidra doesn't complain about any corruptions during analysis.
Turns out IBM uses some weird implementation of the regular CRC-32 checksums. Can't tell if the implementation is normal, off-standard or just weird-looking through the decompiler.
Guess I could identify the memory regions that are included in the checksum check, and what the final value is compared to...but what for? To find out my ROM is corrupt?
Digging into PowerPC assembler is fun, but it won't help me recover the intact image :-/

Maybe someone in continental Europe has a 7006 and could lend me his EPROM for a readout? I'd return it immediately, I promise. Shipping costs and surprise gifts are on me!

JWR

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Nov 8, 2021, 3:43:29 AM11/8/21
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Hi Christian,

ISTR some IPL-ROMs and the like had a kind of safety built in, that is: a copy of the image in a secure, non-erasable portion of its memory. In case of terminal corruption of the working copy, one could copy the safety-copy back into the erasable portion and be back in business.
Maybe??

No 7006 here I'm afraid, sorry.

--
Jelte,
Admirer of the letter of IBM with blue Ishiki

Christian Holzapfel

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Nov 11, 2021, 11:28:52 AM11/11/21
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JWR schrieb am Montag, 8. November 2021 um 09:43:29 UTC+1:
> ISTR some IPL-ROMs and the like had a kind of safety built in, that is: a copy of the image in a secure, non-erasable portion of its memory. In case of terminal corruption of the working copy, one could copy the safety-copy back into the erasable portion and be back in business.
> Maybe??

Hi Jelte. I didn't see any duplicate copy of the BIOS inside the EPROMs address space. This is where you expected it, right?

I managed to come up with a proper RS/6000 style Model M keyboard, the one with the speaker populated on the bottom.
With this one, it goes beyond error 262 (keyboard) in Maintainance mode and now halts at
260 - "Information is being displayed on the display console"

Looking at the serial port 1 with a fully populated null modem cable at 9600, 8N1 shows:


TESTING COMPLETED

A PROBLEM WAS DETECTED. Please write down the following
Service Request Numbers (SRN) and report them to your
service representative.

SRN LOCATION DEVICE
868-099 00-00-0S SCSI port

Press "ENTER" to Continue.


SRN 868-099 refers to "Description: SCSI adapter test failed." Well, thanks for that...

When pressing "ENTER" on the serial terminal (not the keyboard!), the system tries to IPL from the floppy drive.
At least, this is *some* progress.

The IBM document "RS/6000 Diagnostic Information for Micro Channel Bus Systems, Version 4.3.3" mentions a set of diagnostic diskettes.
Are these available as downloadable images anywhere?

JWR

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Nov 11, 2021, 1:48:31 PM11/11/21
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On 11-11-2021 17:28, Christian Holzapfel wrote:
> JWR schrieb am Montag, 8. November 2021 um 09:43:29 UTC+1:
>> ISTR some IPL-ROMs and the like had a kind of safety built in, that is: a copy of the image in a secure, non-erasable portion of its memory. In case of terminal corruption of the working copy, one could copy the safety-copy back into the erasable portion and be back in business.
>> Maybe??
>
> Hi Jelte. I didn't see any duplicate copy of the BIOS inside the EPROMs address space. This is where you expected it, right?
>

Correct. Well, it was a long shot ;)
Shame it didn't work out.

Louis Ohland

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Nov 11, 2021, 1:52:42 PM11/11/21
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Life is a journey. Shame about the destination...

RickE

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Nov 16, 2021, 10:29:26 PM11/16/21
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On Thursday, November 11, 2021 at 11:28:52 AM UTC-5, Christian Holzapfel wrote:

> The IBM document "RS/6000 Diagnostic Information for Micro Channel Bus Systems, Version 4.3.3" mentions a set of diagnostic diskettes.

Back in the early 1990s, I had a very large box stuffed full of the smaller cardboard boxes that held the RS/6000 diagnostic diskette set. The diagnostics version was something like 2.4.1 or 2.4.3. I used these as "scratch diskettes", much as other people used AOL software diskettes. I don't think that I bothered to keep even one set. However, I have a vague recollection that there was a tool on the very early RS/6000 diagnostic CD-ROMs that would create the diskette set -- and I might still have a 2.4.x RS/6000 diagnostic CD-ROM hiding in a corner somewhere.

Christian Holzapfel

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Nov 25, 2021, 3:59:10 AM11/25/21
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Thankfully, Wolfgang read out his 7006's EPROM BIOS and provided me with the image. Turns out, his and mine are byte-identical.
I conclude from this:
- My BIOS is actually intact.
- The BIOS code is not responsible for proper initialization of the onboard SCSI controller.
- An RS/6000 showing a 211 code ("IPL ROM CRC comparison error (irrecoverable)") at startup rather indicates the ROM check being currently processed than meaning a fatal error. This may be different for a 211 stop code, though. Don't make yourself mad.

He also sent me a separate Corvette SCSI controller, which the system happily accepts for installing AIX from a CD-ROM and booting it off the HDD. So the rest of the planar seems to be fine (enough).
The only remaining downside is the heavily extended boot time, while the system passes code 868 ("SCSI adapter being identified or configured") for three times and many minutes each, summing up to over 20 minutes of boot time.

There's still the error message on the graphics/serial terminal that needs manual acknowledge:

"TESTING COMPLETED

A PROBLEM WAS DETECTED. Please write down the following
Service Request Numbers (SRN) and report them to your
service representative.

SRN LOCATION DEVICE
868-099 00-00-0S SCSI port

Press "ENTER" to Continue. "

Pretty annoying.
Running the standard or extended AIX diagnosis for the system planar or the onboard SCSI returns "No trouble was found". Go figure.

I probed the traces from the SYM53C720 SCSI controller IC to the 50-pin SCSI connector and to U24, an IBM proprietary integrated circuit, which seems to be some magic glue to the MCA subsystem. All important I/Os beep through fine, and 5 V power is there, too.
Not sure what the actual problem is, but maybe one day I'll find out.
Swapping out the SYM53C720 SCSI controller IC could be a future task.

Well, thank you Wolfgang, and everybody else here, for making this baby fly again!

~Christian

Christian Holzapfel

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Nov 30, 2021, 8:15:05 AM11/30/21
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Christian Holzapfel schrieb am Montag, 1. November 2021 um 21:53:37 UTC+1:
> And with this video thing... The card is a 11H4913, so it is a "POWER Gt4xi (1-5) 24-bit Graphics Card", according to some awesome know-how site.
> Is its companion, the "Processor Card FRU 52G1343 (Placed in Lower Numerical Slot than Graphics Card)" actually required for the operation?
> There is an empty MCA slot right next to it, so I assume the processor card missing.
> If I recall it right, it's not as simple as dropping in an XGA-2, hmm?

To de-mystify this:
The Graphics Card 11H4913 does not work without a Processor Card 52G1343.
I finally obtained a working couple to test things out. All cards do fine in various configurations, but never without a Processor Card.

Christian Holzapfel

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Dec 29, 2021, 1:54:56 PM12/29/21
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Christian Holzapfel schrieb am Donnerstag, 4. November 2021 um 21:11:38 UTC+1:
> This is the full error code list. I had to use my phone's slow motion video recording function to capture the quick ones.
> Some look pretty fatal to me, indicating some serious planar failures, if they're not exaggerating:
>
> 211 IPL ROM CRC comparison error (irrecoverable)
> 215 A low voltage condition is present (irrecoverable)
> 290 IOCC POST error (irrecoverable)

From SA23-2643-00 "RS/6000 Hardware Technical Reference General Information", chapter 6-12, describing the Power-On Self-Tests:

"Before calling a POST routine, the controller puts a value in the LEDs identifying the POST
so that if there is an error while running a POST and control does not return, the error is
identifiable."

So if evil error codes show up, don't get nervous. If they disappear, it's all fine.
Good to know.

Christian Holzapfel

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Dec 29, 2021, 2:09:34 PM12/29/21
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Christian Holzapfel schrieb am Mittwoch, 3. November 2021 um 14:33:37 UTC+1:
> What baffles me is that none of my HDDs likes to spin up when connected to the internal 50-pin SCSI port.
> I've disabled the external port (due to lack of a proper terminator), tried two different 50-pin cables and two disks.
> They all spin up fine without the SCSI connected, so power is there.
> Tried some 9.1 GB SCA drive with an adapter, and an IBM DALS-3540 (540 MB, set to ID 3, spin up, termination on).
> Is there a special cable required, is the planar toast or am I missing anything else?

Finally solved the issue. Wow.
If you're in deep, reverse-compiling the BIOS, resoldering 208-pinned SCSI controllers on multi-layer PCBs, put everything aside and let it sit.

Three learnings:
- Even with the external SCSI port set to "disabled" and active termination on the internal bus, a proper termination plug for the external connector is required.
- Always have more terminators at hand than you think you need.
- Scrap those nasty operator's and service guides, that don't mention this essential plug at all, and don't show it in the pictures.

I have not tested the internal SCSI port, as Wolfgang's Corvette is doing an unsurpassable job with it's wide-SCSI messaging.
Proper I/O subsystems are a joy.
Finally, the system does not hang with the "internal SCSI port trouble" message at startup, and boot-up time has come down from over 20 minutes to around 3-4 like any other RS/6k system.

Thanks to all for putting on the water wings...

Louis Ohland

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Dec 29, 2021, 2:37:03 PM12/29/21
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Some feelthy-feely full frontal pictures of the SCSI chipset and areas
by the external ports?

It might be the internal port has adequate self termination, and the
external port, not so much.

Louis Ohland

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Dec 29, 2021, 2:41:46 PM12/29/21
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https://ardent-tool.com/IBM_SCSI/SCSI-FW.html#FW_Rear

Note the term networks on the rear? A pair of 89F7000 for the internal,
a pair of 89F7000 for the external. Does your Magical machine have a
similar setup?

Louis Ohland

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Dec 29, 2021, 2:52:48 PM12/29/21
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I looked at one pic you put up. I see the SYM SCSI controller, but am
not seeing any terminating networks. All I notice is the TERM PWR PTC
for the internal and the TERM PWR PTC for the external bus.

On 12/29/2021 13:09, Christian Holzapfel wrote:
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