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Radius IIsi NuBus Adapter

nathall

Active member
Anyone have any information on the IIsi NuBus Adapter from Radius? I can't find any information about it online, only a couple pictures here on this forum regarding an SE/30 project. Documentation, first hand experience, etc? Is it compatible with all the same cards the Apple adapter is?

I'm also curious if the empty socket on it is for an optional FPU.
 

Melkhior

Well-known member
The socket is very likely to be for a PLCC '882, as that is a common feature of IIsi adapter and it is the appropriate one in the picture (68 pins).

Other than that, the front side is using six 74ALS648 as bus transceiver. Apple used eight74ALS651 in their discrete implementation (before switching to custom fully integrated 16-bits parts, each replacing four ALS651). The '648 vs '651 isn't a big deal, it's a slightly different set of control pins (GAB/~GAB on the '651, ~OE/DIR on the '648). What's interesting in the six vs. eight bit. Each '6xx is 8 bits and you normally need to buffer both the '030 data bus and address bus to the mutiplexed NuBus signals. Radius might be able to get away with driving some pins directly from the GAL/PAL as there's only a single slot? (or there could be more chips hidden on the back of their adapter!).

I would also love more details on this adapter, as it is the one NuBus host implementation I know if where all the parts are still available.
 

nathall

Active member
I have one that I picked up to replace my Apple one that was damaged in a Maxell bomb. I’ll try throwing a 68882 in that socket and see if the computer recognizes it.

Some curious things I noticed while playing around with it. If you install it but don’t install any NuBus cards on it, the computer won’t boot. You get the chime, and then nothing, just a black screen. I’m wondering if this is because the IIsi disables the onboard video when it detects the adapter, even if there’s no video card on it. Trying to start up with an Apple NuBus video card installed causes no boot and death chimes, hence my compatibility question earlier.

It’s currently installed and running a Radius video card, the same one that I had installed when I had the Apple adapter. Works great for that.

I have some NuBus Ethernet cards around that I’ll try eventually.
 

Melkhior

Well-known member
I’ll try throwing a 68882 in that socket and see if the computer recognizes it.
Beware the orientation of the '882, they will fit in the PLCC socket even the wrong way... the socket should have some indication where pin 1 is supposed to go (in a PLCC package it will be in a middle of a side, not in a angle).

Some curious things I noticed while playing around with it. If you install it but don’t install any NuBus cards on it, the computer won’t boot. You get the chime, and then nothing, just a black screen. I’m wondering if this is because the IIsi disables the onboard video when it detects the adapter, even if there’s no video card on it. Trying to start up with an Apple NuBus video card installed causes no boot and death chimes, hence my compatibility question earlier.
It’s currently installed and running a Radius video card, the same one that I had installed when I had the Apple adapter. Works great for that.
I have some NuBus Ethernet cards around that I’ll try eventually.
Interesting. It suggests the NuBus implementation Radius did isn't fully compliant, and might just be designed to support the subset needed by Radius devices. Not booting without a device suggests the NuBus implementation doesn't timeout when addressed, so the CPU hang when the ROM probes the NuBus memory space. It's weird that it doesn't boot with an Apple video device though - those should be fairly simple (no bus mastering, ...).
 

Trash80toHP_Mini

NIGHT STALKER
Might that adapter be capable of polling the display card's ID in the IIsi? I wonder if there was an extension or control panel paired with that adapter?

Not likely though, as @Bolle reports most any card he's tested as working in the SE/30 using Radius' NuBus adapter, albeit at only 8MHz. I wonder if the SE/30 exhibits similar behavior? Again, I'd think not, there's likely no NuBus memory space polling by its stock ROM?

Will the "Dirty ROM" of its IIcx sire even boot the SE/30?
 
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nathall

Active member
I wanted to follow up that I tried this adapter with a different Apple video card (16-color High Resolution Video Card) yesterday and it boot up and ran, so maybe there’s an issue with the previous Apple card I tried and not the adapter itself. Will follow up with more.
 
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