ardent-blue
Experienced Member
- Joined
- Jan 2, 2015
- Messages
- 479
While I was treading to and fro on the world, MAJ Tom managed to use the Ionosphere and skip me a message about a small PCB on the 8556 system board. In particular, "J21" is [was] a three pin header, but now has a small PCB on it, porpoise unknown. Look at the upper left, below the yellow DIP resistor network.
http://www.supervinx.com/OnlineMuseum/IBM/8557/045/004-01012068.JPG
The double row of "LC" components caught my eye. What kind of a circuit would they be part of? 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].
https://www.ardent-tool.com/RS6000/FPT-18_Example.jpg
After looking at 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. Before the uninitiated suggest I RTFM, Texas Instruments fabbed these chips especially for IBM. Note the "CF" prefix. CF in short means there are no datasheets. Special mojo chip.
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 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]? How does an LC device function in a filter, as opposed to discreet L, C, and R components?
The truth is out there...
http://www.supervinx.com/OnlineMuseum/IBM/8557/045/004-01012068.JPG
The double row of "LC" components caught my eye. What kind of a circuit would they be part of? 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].
https://www.ardent-tool.com/RS6000/FPT-18_Example.jpg
After looking at 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. Before the uninitiated suggest I RTFM, Texas Instruments fabbed these chips especially for IBM. Note the "CF" prefix. CF in short means there are no datasheets. Special mojo chip.
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 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]? How does an LC device function in a filter, as opposed to discreet L, C, and R components?
The truth is out there...
Last edited:
