Blizzard 1260 - SCSI-IV trouble

[Hyperspeed]

I have a Phase5 Blizzard 1260 accelerator board and a DCE SCSI-IV
adaptor (v8.5 ROM) but I tend to get a lot of "There is a Checksum
Error on xxx".

When I click retry the error vanishes!

I have changed memory from EDO to FPM, have active termination on the
last device, cable length appropriate for Asynch mode and I have used
only Phase5 utilites for HD prepping (no mixing prepping tools).

I can't work out why I get these sporadic errors, am I picking up RF
interference? My cable length is 2.5m including internal and the
scanner. The limit for Asynch SCSI-1 is 4m...

When I squeaze the SCSI-IV to 25-pin plug the error sometimes doesn't
re-occur as though I'm absorbing RF or making a better contact ont he
pins.

I've changed cable though and the problem is still there! I've heard
about increasing the Error Retries but surely this is a sign of a bad
chain in the first place!

Help me SCSI-IV users!

[blobrana]

Hum,
Yes it could be RF interferance (cured by passing cables through  ferric rings - or nuts),
But it sound like transfer speed is too high for the HD buffer.
(sry, don`t have info on what the settings should be, SCSI-IV is beyond me)


good luck

[Trev]

The first question I'm always asked when reporting these types of problems is, "What power supply are you using?" Using the stock A1200 power supply on an expanded system isn't recommended. (Please note, however, that I use the stock power supply on my AT Amiga 1200 / DCE Blizzard 1260 / Phase5 SCSI-IV kit combination without incident.)

Trev

[Castellen]

Is that the SCSI controller that uses the elastomer (zebra) strip for the electrical connections to the Blizzard board??
They seem to have a problem where the contacts become oxidised/contaminated, so start causing all sorts of intermittent problems.

I'd suggest wiping the elastomer strip and the contacts on the PCB with some isopropyl alcohol then reassembling it.  Don't touch the cleaned surfaces with your fingers, or you can recontaminate the contacts.

I've heard some people say boiling the elastomer in water also fixes it?!  I probably wouldn't recommend that unless you have a spare strip.

[Hyperspeed]

I'm not sure what a zebra strip looks like. What's on the DCE SCSI-IV
kit is like a little female block with curly pins inside, like smooth,
springy things that squeaze onto the PCB of the Blizzard 1260
mainboard.

The 1260's gold contacts became very yellowy like matt-yellow and not
shiny gold so on the SCSI-IV expansion connector I use a blunt tweezer
to scrap off the oxidisation to make it shine again (making sure not
to scratch but to gently ebrase (whilst keepign earthed).

This seemed to work for a while ontop of the FPM (which replaced the
EDO SIMM), but things have gotten worse recently.

I have a converted PC PSU so plenty of juice and I've tried varying
cable length and drive combinations to no avail.

The trouble is my Mask/MaxTransfer setting is set to Zorro3 hex speeds
that can go up to 16mb/s...  this concerns me and I'd like to try the
settings for the same speed as an IDE drive just for curiosity.

Any ideas?

[Piru]

The trouble is my Mask/MaxTransfer setting is set to Zorro3 hex speeds that can go up to 16mb/s... this concerns me and I'd like to try the settings for the same speed as an IDE drive just for curiosity.

MaxTransfer has nothing to do with transfer speed.

MaxTransfer is the maximum size of the block that can be transmitted in one operation. Larger operations are split into MaxTransfer chunks. 16MB (0xfffe00) MaxTransfer doesn't limit the speed to 16 MB/s.

Typically all SCSI devices should be able to handle 16MB (0xfffe00). IDE devices handle 128K (0x1fe00).

[Hyperspeed]

Castellen, what about the trapdoor expansion connector... does that
oxidise over time too?

I thought gold was chosen for connector because gold does NOT oxidise.
Has Phase5 been sold some brass and fobbed off as gold?

:-)

Does Isopropyl Alochol dissolve tarnish or just finger grease?
Wouldn't I need something like Brasso medal polish or something to
shine up the contacts?

I do get more reliable performance when I remove and re-install my
B1260 + SCSI-IV but I'm more suspicious of the dodgy 50-pin to IDC
adaptor that I made myself. It makes circuits but I'm not sure about
insulation or shielding.

I heard that you must remove a terminator if your chain combines
internal and external cables...

Any ideas are greatly appreciated!