I made a crude, ugly connector for this card, but so far I connected the several SENSE and SYNC lines plus the associated grounds only. No coaxial cables were soldered thus no picture would be possible; but at least I could check if my versatile Acer monitor syncs up properly with the card's (partial) output. Some evidence of this outrage:
Now, the testing: I used a IIsi with 33 MB and System 7.5.5. An Apple 12" RGB was connected to the internal video output (to be able to see what was going on) while the Acer was hooked to the ColorPivot thru a typical, known good VGA adapter (and my cable).
Upon power-up, during the RAM test (33 MB do take a while on the IIsi!) both outputs were muted, as expected... but as soon as the internal video arose, the Acer detected some signal too! No picture of course, but from its menu there was a 68 kHz / 75 Hz signal, like that of a Portrait display -- confirming my previous probing with the oscilloscope. However, this was always the same any way I went with the VGA adapter's switches, plus it never showed up on Monitors control panel although Gauge series's Slot Info was detecting it properly every time (slot $A). Warm restarts make the sync signals to the Acer disappear for a moment and then back again, as expected.
On the other hand, I recently got (from macmetex too) a Radius Pivot NuBus Interface (632-0070). Sharing the same DRAM (8x M514252A-80, just different package), the same big custom chips (297-0308 & 297-0309), the RAMDAC (Bt478KPJ50), the famous 14.3181 MHz crystal can and regulators (LM385 & LM393) plus most discrete components, I don't think it's crazy to assume both cards would have similar capabilities... even the ROM (DIP vs. PLCC) is labeled quite much the same: (C) 1992 Radius Inc. COLOR PIVOT V2.6 256K U5-0039-04-A (the PLCC version reads CLR/PVT V 2.6 0048-2A, there's much less space on it)
This NuBus card has the usual DA-15 connector, so I could easily check that it supports several display modes:
- 512x384, 60 Hz (12" RGB)
- 640x480, 66 Hz (13", not VGA)
- 832x624, 75 Hz (16")
- 640x870, 75 Hz (Portrait)
But whenever I had any other mode set on the adapter's switches, it kept displaying the usual grey screen with the Radius logo at the bottom at the "default" portrait mode: 640x870, 68 kHz, 75 Hz; looking very stretched on the wide Acer monitor -- not the safest thing to do if connected to a fixed-frequency incompatible monitor Of course, when on a compatible mode the Radius logo appeared for a moment, then the Mac cleared the screen and started booting, as expected.
Could it be that somehow the Pivot IIsi is not detecting a compatible monitor and thus disabling itself? Maybe when I get the coaxials soldered it could show the Radius logo, as the 'scope-detected activity on the RGB lines suggests. BTW, the sense lines' continuity on my crude cable checks out OK...
I hope to be able to complete the task in a few days, and come back with more info. I can't conclude anything so far