Black Terminator for the IIfx

[Tempest]

Does someone have a picture or better yet specs of the legendary black IIfx terminator? My IIfx didn't come with one so I'm either going to have to buy one, find a compatible one, or build one. Are there compatible third party terminators that will work?

Tempest

 

[ppuskari]

If no one gets to it first, I can at least photograph it for you. I was luck enough to get one in a random conquest a year or so ago. Now I have 2 dead iifx machines (battery acid attacks), and one other mobo just sitting with the same condition...One day I'll get one to work!

But I'll get the picture up later for you. It looks IDENTICAL to a standard SCSI termination block.... I never did find out what was so special about it. I'm thinking maybe it is some sort of pseudo active termination? ties back the 5v line to pretend to be active termination maybe?

I'm hoping someone can post up the schematic for that beast if they have it. I would certainly love to find out what the deal is with that black termination block.

 

[Trash80toHP_Mini]

. . . I never did find out what was so special about it. I'm thinking maybe it is some sort of pseudo active termination? ties back the 5v line to pretend to be active termination maybe?

I'm hoping someone can post up the schematic for that beast if they have it. I would certainly love to find out what the deal is with that black termination block.

IIRC, there's no schematic and no active termination, it just has resistor packs that're "stronger" than the "standard' terminator's spec.

Dunno what the value is offhand, but I've got GttMFH: Second Edition, so i can look it up later. Try checking the DevNotes, you'll probably find the answer faster, i can't post it until tomorrow, IF i remember to look!

You might also try googling for the resistance differential. [] ]'>

 

[Osgeld]

searching "macintosh IIfx terminator" fourth link down brings up an old apple doc

http://support.apple.com/kb/TA42169

searching "apple part number 590-0705" second link brings up these people

http://www.seadec.com/iqnewequip_1.html

which seems to be some old new stock surplus place, anyway searching that page states they have 50 of the (not black but compatible) -A models in stock, email for info

fu>

 

[beachycove]

I read on here a couple of months ago from one of the resident technologoi that the termination supplied by later 50-pin scsi drives is usually sufficient for a IIfx; the black terminator in question dates from a time when termination technology was not built into hard drives. So as I was at the time trying to get a IIfx running, and had no terminator, I gave it a try and I can report that my IIfx definitely works fine without the special unobtanium terminator. Not a single hitch, and running 6.0.8 in "wicked fast" IIfx fashion.

I think the hard drive I put in mine was in the 250-500MB range. If you have two or three old drives lying about, and most of us do, try one and see where you get.

You need good batteries, however, or it will not boot.

 

[Tempest]

Yeah I'm still having problems with the booting. I put new batteries in it and get the starting chime, but nothing after that other than a click or two. I tried resetting the PRAM, but still nothing. It never gets to reading the disk drive, and I have no idea what's wrong with it. I have another thread about that though.

Tempest

 

[Dennis Nedry]

I've heard that you can use two normal terminators in a row and it acts similar to a black terminator on the IIfx. I don't have a citation for this though.

 

[ppuskari]

That certainly would make some sense electrically if all that is different is a higher ohm rating of the total termination value.

Might have to try that at some point when I have free time and get a working iifx motherboard. So many projects and so little time.

 

[Dog Cow]

According to the hard drives article (page 120) in December 1990 MacUser, "the Mac IIfx differs from previous Macs in that it requires so-called black terminators with built-in filter capacitors that 'absorb' short pulses that the SCSI controller chip might otherwise interpret as control signals."

 

[jruschme]

Tempest,

Would you be looking for a black terminator? A couple of days ago, I found my old one (got rid of the IIfx some time ago).

John

 

[Tempest]

Yes I desperately need one for my IIfx. I'll send you a PM.

Tempest

 

[Trash80toHP_Mini]

I haven't looked at the specs, but it's probably not a big deal to change out the internal terminator packs with the "proper value" of resistor to create an on-board Black Terminator on the MoBo. As for the definition of filtering out noise, that's what ALL terminatino resistors are for and are normally present on the ends of any properly designed cable driver setup.

IOW, Apple goofed on the firs rev IIfx MoBo run and then kept making them wrong to avoid confusion first, and to cover up their MoBo design level error, second!

IMHO, of course!

 

[Osgeld]

yea it should not be hard to add the termination, but resistors alone do nothing for noise, you need a rc network

by the time you figure out what noise is present and do the math it might be easier just to buy a terminator

and if anyone read my google fu post IT DOES NOT NEED TO BE BLACK! they made these things in 3 revisions, the black one, the A model which is beige / plat, and a C revision which is kind of a generic catch all after the fact and the II models started hitting the second hand market and needed more dongles

dont get me wrong I understand why you want the black one, but if I were itching to get my IIfx up and running (and I would) I would just snag the first one I could get my hands on then worry about authenticity at my leisure

 

[Dennis Nedry]

I booted your IIfx from an external hard drive without a terminator at all Tempest. I think it depends a little on your drive too. Terminators are tricky and unpredictable as to when you need them and where, but I would imagine you could find some configuration that doesn't require a real black terminator.