Scsi confuses me big time..

[Gav]

Ok i have a 1200 blizard 060 machine with the scsi 2 add on.
I have had the scsi 2 for well over one year now and all it is doing is being used to hold my extra 64mb simm.Im used to ide so have no idea on scsi at all.Well i have the lead that comes for the scsi 2 which has a connector on it.I also have a lead with a few scsi heads on it for hd,cd and whatever else.So what type of adaptor do i need to connect these together??? would one of these do???    http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&category=41993&item=3483262960&rd=1
But im thinking that this is the thing i need???  http://www.powerc.com/cgi-bin/psearch.cgi?code=500-0009&rn=783&aid=&uid=ssXh1hMJTrR/.7I&sid=&cid=4&act=gpage
 See i have a scanner ready to be used which is a umax1220s and have had it ages along with scan quix.If someone could explain it to me and point me in the right direction of the actual stuff i need to buy such as terminators,adaptors,leads and what not that would be really great as im stuck.
Thanks again for all the help..
Gav


Or maybe this also?     http://www.powerc.com/cgi-bin/psearch.cgi?code=500-0035&rn=783&aid=&uid=ssXh1hMJTrR/.7I&sid=&cid=4&act=gpage
 Thanks

[theTAO]

Do you have a SCSI cable for your scanner (external, DB25 male to DB25 male)?  If so, and you don't currently have plans to use other SCSI devices, then you shouldn't need an adapter at all.  The 1230 SCSI cable and the scanner cable should connect just fine. :-)  External SCSI devices are generally always 25-pin, while the pin count for internal devices vary (50, 68, 80 ?, etc.).  Just make sure termination is enabled on the scanner.  I own a UMax scanner myself (a hulking 1200S) and recall that some UMax scanners do poor internal termination...but for just one device on a short cable, this shouldn't make a difference.

If you eventually decide to add internal devices, you'd want the 25-50-25 adapter from Power Computing.  Until I saw your link, I had no idea such things actually existed!  I made my own adapter a number of years ago and it was a hellish experience, but it did work on the first try.  It's currently powering a Seagate hard drive, a Plextor 40x CD-ROM, a Plextor Premium CD/RW (via an IDE to SCSI adapter), a 250MB Zip, and the UMax, and it all works very well.  It annoys me that Phase5 or DCE never put a 50-pin connector on the 1230 SCSI (since it's much easier to go from 50->25 than the other way around), but it is a useful little board.

Hope that helps,

Todd

[Gav]

Hi
Yes that did help,thanks mate..I just bought myself a 25 pin lead off ebay as the one i got with it had a 25 pin on one end and a wide scsi on the other.
Yes soon enough i will plan on adding internal devices but for now its just the scanner.Is scsi better than using ide??as i have a powerflyer gold mk2.
Thanks for the help since i can actually put my scanner to some use now.
Gav

[Neo]

I say SCSI should give best performance in your case. Not for that it's SCSI but because it's tighter integrated with your accelerator (CPU) board. I do not know the specific performance of your SCSI addon though, so I might be wrong.

[AdMartin]

SCSI is generally faster than IDE. But that's not the same as saying it's better, that depends on what you're using it for. On a PC, IDE is usually enough. Even though SCSI would be faster, the cost would be disproportionally high. On Amiga it's a different matter, though, as no IDE controllers for Amiga use DMA. DMA is a way for the controller to shuffle data directly between the device and memory. Since DMA is unavailabe on Amiga IDE controllers, they have to go through the CPU for every transfer, which slows the computer down substantially. Therefore, SCSI is highly recommended on Amiga computers. With a SCSIDE bridge like this you could use a cheap IDE drive on the SCSI controller and thus bring the price down.

/Martin

[AdMartin]

I don't know what the connector on your SCSI interface looks like, but it's unfortunate that the standard lead has a 25-pin connector. If it's possible to exchange it for a lead with a 50-pin connector that would be advisable, but maybe that's not an option. The 25-pin D-Sub connector was originally introduced by Apple to keep down costs. The connector misses the ground wires, which brings down signal integrity. External SCSI devices intended for use with other platforms (than Apple or Amiga) originally used a 50 D-Sub connector before the 50-pin Centronics connector was introduced. Nowadays 50-pin or 68-pin High Density D-Sub or 68-pin Very High Density (micro-Centronics) connectors are used for external devices.

Anyway, the Power SCSI adaptor you found can be used if you want to connect an internal hard drive. Note however that only two of the connectors can be used at any one time. You could probably find a converter with just two connectors cheaper (Ebay, anyone?). I guess the standard lead you own has a DB25 connector, so the converter should have one DB25 and one male IDC50 connector. A cable like this would be needed to connect the hard drive and/or CD drive. If the hard drive has a 68-pin connector you'd need a 68-pin --> 50-pin converter, like the ones you linked to in your post. Just make sure the converter terminates the high bits. 68-pin devices uses 16-bit transfers and 50-pin devices only 8-bit transfers. So the high bits of a 68-pin device must be terminated when connected to a 50-pin chain.

I guess you want the scanner at the end of the chain and in that case you'd need another converter to go back to 25 pins... If the termination on the scanner is dodgy, you might need a better terminator, like this one.

Hope this helps. :-)

/Martin

[motrucker]

  Another advantage to SCSI is that you can put up to 7 devices on one SCSI buss. This can be a huge help! Just whatch the overall cable length.

[QuikSanz]

Hi,

There is one thing being missed here. SCSI can also read & write at the same time, with good DMA access this speeds things up a lot.

Chris