@max1zzz
I realize your aim was merely to
recreate the original motherboard 1:1, but I am curious about trace widths and the power able to be supplied to the
NuBus slots.
It seems that Apple specifies a "budget" of
6.0A max for all the NuBus slots combined, and
2.0A budgeted for each NuBus slot. It's not clear if that 6.0A is merely a slice of of the 5v current output of the stock PSU, or if that is limited in some way, either through active circuitry or indirectly by the thinness of PCB traces.
WARNING!: The
IIci Technical Procedures document is in
ERROR when it wrongly says
EACH NuBus slot is allocated 12.0A:
(5V @12A= 60W, not 10W. 5V @2A = 10W, which is what they meant to write.)
I have a 33MHz 68040 Radius Rocket with 32MB RAM in my IIci, which is a config rated at
3.0A @5V:
I also have a Radius Thunder 24GT NuBus video card which is marked on the card itself as being
3.3A @5V:
Because 3.0 + 3.3 =
6.3A, I am already over budget for my IIc's NuBus slots (both in terms of total current draw and per-slot draw), and I still have one NuBus slot free! (Even so, the machine does function with a recapped stock PSU.)
Now consider the current consumption required if a second Radius Rocket were to be installed in that same machine (which is allowed by Radius if the Mac in question is able to power all the cards properly). No, I don't have two Rockets. I am just pondering the current consumption issues.
There has been talk about new, modern power supplies for the IIci, some which can offer more power than the stock PSU. But if there is something that LIMITS current flow to the NuBus slots in a IIci, be that active circuitry or indirect limiting by thin PCB traces not able to pass the current, a beefier PSU would largely be wasted. A big reason to have a more powerful PSU would be to supply more current to power hungry add-on cards. (Consider well you can even add a Daystar Turbo040 in the cache slot at the same time you also have a Radius Rocket installed.)
Max, because you spent a lot of time recreating the IIci motherboard, examining trace width and length, along with the components too, I would love to hear your thoughts on the PSU and power consumption by the slots.
Thanks!
github.com
