While I was treading to and fro on the world, MAJ Tom managed to use the Ionosphere and skip a message on a small PCB on the 8556 system board.

http://www.supervinx.com/OnlineMuseum/IBM/8557/045/004-01012068.JPG

In particular, "J21" is [was] a three pin header, but now has a small
PCB on it, porpoise unknown.

What caught my unfocused eyes was two rows of "LC" components. MAJ Tom
has just recovered from filming an episode where his co-star mistook his wide-eyed naivety for inexperience. You know, "I've never done this
before" and things went... downhill. Helga made it look like Tom fell on
the ice... Repeatedly. Like a Russian oligarch on Putin's bad side... I
hope MAJ Tom doesn't smoke in bed...

https://www.ardent-tool.com/RS6000/FPT-18_Example.jpg

I am not saying that the LC components are a direct match to the Forced
Perfect Termination [FPT], but we have LC1 - LC18. We are in the SCSI
nexus [SCSI components concentrated here].

After czeching the 8556 and 9556 pages, I noticed a disturbance in the
Force. Where "LC" components are used, TI controller 64F4760 / CF63290PC
-or- 91F9906 / CF63323PCM is used.

After a few decades of hedonistic sampling of IBM boards, an "LC"
component is uncommon. Read that as I can't remember seeing one before recently.

Now, MAJ Tom has noted other boards with discreet L and C combinations.
True dat. But that isn't the reason for my curiosity.

Must be an odd component, is it a slurry mix of ingredients, or is there
a core surrounded by a [reactive] coating? One crude concept - like an inductive core, surrounded with a capacitive coating?

Now's time for a SWAG [not quite the level of a S.H.I.T.] and wonder why
IBM chose to use an "LC" component instead of discreet components.

Space ? System board trace complexity? Is it something that TI chips
needed [part of a provided design by TI]?

What are the SCSI chipsets used for system board SCSI, and what internal termination arrangements do they use? I started a list of on-board SCSI, 8556/57, 9556/57, Bermuda, P75, 85-X, then added the chipset for the
Tribble and Spock.

The truth is out there...

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

What should I tell you, Helga's too thicc and likes experimenting...

Anyway, the ferrite beads are there for filtration purposes. I don't
think they have anything to do with FPT (and I don't see any diodes near
the SCSI connector either; CR1-4 are clamp diodes for the RAMDAC). But
the J21 module is a bit sus. Will have to probulate that too, once I get
my hands on a 8556 planar.

Dunno why they used "LC" for the ferrites, usually they are marked "L"
(because they are inductors primarily) or "FB".

It doesn't matter IMO. The 8556 has more interesting secrets to offer. :)

On 01.02.2023 12:29, Louis Ohland wrote:

While I was treading to and fro on the world, MAJ Tom managed to use the Ionosphere and skip a message on a small PCB on the 8556 system board.

http://www.supervinx.com/OnlineMuseum/IBM/8557/045/004-01012068.JPG

In particular, "J21" is [was] a three pin header, but now has a small
PCB on it, porpoise unknown.

What caught my unfocused eyes was two rows of "LC" components. MAJ Tom
has just recovered from filming an episode where his co-star mistook his wide-eyed naivety for inexperience. You know, "I've never done this
before" and things went... downhill. Helga made it look like Tom fell on
the ice... Repeatedly. Like a Russian oligarch on Putin's bad side... I
hope MAJ Tom doesn't smoke in bed...

https://www.ardent-tool.com/RS6000/FPT-18_Example.jpg

I am not saying that the LC components are a direct match to the Forced Perfect Termination [FPT], but we have LC1 - LC18. We are in the SCSI
nexus [SCSI components concentrated here].

After czeching the 8556 and 9556 pages, I noticed a disturbance in the
Force. Where "LC" components are used, TI controller 64F4760 / CF63290PC
-or- 91F9906 / CF63323PCM is used.

After a few decades of hedonistic sampling of IBM boards, an "LC"
component is uncommon. Read that as I can't remember seeing one before recently.

Now, MAJ Tom has noted other boards with discreet L and C combinations.
True dat. But that isn't the reason for my curiosity.

Must be an odd component, is it a slurry mix of ingredients, or is there
a core surrounded by a [reactive] coating? One crude concept - like an inductive core, surrounded with a capacitive coating?

Now's time for a SWAG [not quite the level of a S.H.I.T.] and wonder why
IBM chose to use an "LC" component instead of discreet components.

Space ? System board trace complexity? Is it something that TI chips
needed [part of a provided design by TI]?

What are the SCSI chipsets used for system board SCSI, and what internal termination arrangements do they use? I started a list of on-board SCSI, 8556/57, 9556/57, Bermuda, P75, 85-X, then added the chipset for the
Tribble and Spock.

The truth is out there...

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)