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AuthorTopic: MKII SCSI Mod.  (Read 1477 times)

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Offline ZXoney

MKII SCSI Mod.
« on: June 30, 2006, 04:43:42 AM »
Anyone out there in need of the SCSI mod for a MK-II?

I got one as a bonus with my CSPPC that has UltraSCSI built in, and wouldn't work with it anyway!

ZXoney
 

Offline doctorq

Re: MKII SCSI Mod.
« Reply #1 on: June 30, 2006, 06:53:44 AM »
Which SCSI chip has it got? My current MK2 SCSI controller can't cope with overclocking, so would like to try out another SCSI kit.
 

Offline orange

Re: MKII SCSI Mod.
« Reply #2 on: June 30, 2006, 07:30:34 AM »
I need it, how much are you asking?
Better sorry than worry.
 

Offline X-ray

Re: MKII SCSI Mod.
« Reply #3 on: June 30, 2006, 09:58:18 AM »
If the previous two posters don't want it at your price, there is a guy on EAB who has been looking for one. I can't remember his name, but he asked me for mine a while ago. Advertise there if you don't make the deal here.
 

Offline ZXoney

Re: MKII SCSI Mod.
« Reply #4 on: July 01, 2006, 03:00:27 AM »
Just posted it on ebay so have at it!

here is the link http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ih=010&item=200003293300&rd=1&sspagename=STRK%3AMESE%3AIT&rd=1


Good luck to you all..

-=(ZXoney)=-
ZXoney
 

Offline X-ray

Re: MKII SCSI Mod.
« Reply #5 on: July 01, 2006, 05:22:34 AM »
@ ZXoney

That unit should have two PCBs and two ribbon cables. Are these included or did you only get that one PCB? Check my pictures in the photo album to see what I mean.
 

Offline ZXoney

Re: MKII SCSI Mod.
« Reply #6 on: July 01, 2006, 07:36:29 AM »
Sorry but no, from the picture it looks like nothing more than a termination block on a backplane, I have a 50pin to 25 backplane I'll throw in if you win and want it? Or does this daugther Card do more than give external connection and act as a passive terminator?

ZXoney
 

Offline doctorq

Re: MKII SCSI Mod.
« Reply #7 on: July 01, 2006, 07:59:09 AM »
Well, since it's US and Canada only I'm out.
 

Offline Ilwrath

Re: MKII SCSI Mod.
« Reply #8 on: July 01, 2006, 11:44:08 AM »
Quote
Or does this daugther Card do more than give external connection and act as a passive terminator?


Yeah, I think the external connector and passive (or active?) termination are all that the daughter card provides.  You do need it (or an equivalent) plugged in for the main card to function properly, though.  Otherwise you'll introduce SCSI errors and get degraded performance.  Finicky cards...

 

Offline Zac67

Re: MKII SCSI Mod.
« Reply #9 on: July 01, 2006, 12:27:25 PM »
Looks very much like active termination - passive ones do not work by setting a jumper, instead you'd remove the resistor arrays.
 

Offline ZXoney

Re: MKII SCSI Mod.
« Reply #10 on: July 01, 2006, 10:18:45 PM »
This is true most of the time when dealing with the Hard Drive and older scsi controlers like my A3000's, but the resistor array is x# of resistors with only one ground! so no jumper no ground no termination.. I have a few external SCSI boxes and all have a two position swith for termination.. Either way Active or Passive, you can still get internal termination blocks that connect to the 50pin cable to do the same job..

Good point though!

-=(ZXoney)=-
ZXoney
 

Offline ZXoney

Re: MKII SCSI Mod.
« Reply #11 on: July 01, 2006, 10:25:18 PM »
Not so, If you are a "Amiga.org" member I will gladly ship to you world wide! Shipping cost will be actual cost, no handling charges.. I'll do this here because I know its going to a real Amiga user and not some one just looking to get it cheap and resale for more! Lota that crap on ebay!


-=(ZXoney)=-
ZXoney
 

Offline Zac67

Re: MKII SCSI Mod.
« Reply #12 on: July 01, 2006, 10:39:14 PM »
Hate to be {bleep}in', but
- trying to deactivate a passive terminator pack just by disconnecting GND is no good idea - and probably not very stable either. You'd have to disconnect 5V, too, and still have the data lines loaded with floating resistors
- the BBoAH Pic clearly shows two UC5603DP active termination chips
 

Offline ZXoney

Re: MKII SCSI Mod.
« Reply #13 on: July 02, 2006, 12:01:54 AM »
Good point, I just looked in the back of my CD-R box and the terminator switch runs to a jumper on the drive itself, so I guess that kills the 5v+ and not ground, didn't think about the resistors floating, guess that would cause errors! :bow:

So, the question is can this board be bypassed? And if so how would we connect the active terminators? One on the end of each 50pin connector? Or both to the external?

With both active terminators being connected to the external connecter of this pcb I would think that the internal connecter is wired in next to the controller and the terminators on either end of the chain? So both internal and external devices can be connected to the external connector like this:

internal and external devices being used:

(active term)======(external device)======(SCSI Controller)===(internal device)===(active term)

or

(active term)======(SCSI Controller)===(internal device)===(active term)

for only one device being used?

"===" is of course the 50pin ribbon cable..

-=(ZXoney)=-
ZXoney
 

Offline Zac67

Re: MKII SCSI Mod.
« Reply #14 on: July 02, 2006, 09:35:15 AM »
The floating resistors would more or less just put a load on the bus - with only a few devices that might be forgivable but I wouldn't really try. But I've never seen passive terminators that could be disabled with a jumper.

Your termination schemes are correct, without the backplane board you'd still have to terminate both ends of the SCSI chain - if only one host adapter connector is used, the other needs some kind of terminator.

I usually disable all passive terminators I find and replace them with active ones, that can be switched much easier.