Disabling SCSI on a Blizzard SCSI Kit MK IV

[Blinx123]

As the Blizzard SCSI Kit is pretty much the only way I can add more memory to my desktop Amiga 1200 and I've already bought a 128MB 50ns EDO for it, I'm very much interested in this.

Can the SCSI feature on a Blizzard SCSI be disabled (either in software or by soldering/desoldering)?

I don't really care about SCSI, since I'll towerize and equip it with a PCI SCSI card eventually.

However, I'd very much like to have access to 256MB while keeping my future Blizzard 1260 at it's 77MHz.

[Bamiga2002]

What's up with disabling it? It won't cause any harm . I think for disabling it you need to use "SCSIControl" or "UnitControl" tool to disable or to reduce boot-time IIRC.
It's been a long time since I had my SCSI-IV kit that's sold now .

[Zac67]

'On-accelerator' SCSI can be much faster than any Z II, Z III, or subsequently PCI card - it has direct access to the accelerator RAM w/o being slowed down by a slow bus connection.

PCI is a slight exception as DMA into (video) RAM on the PCI bus can even be much faster even - but the CPU would need to use the slow bus to get at it.

Plus, you won't be able to boot from any PCI SCSI HBA.

[Blinx123]

'On-accelerator' SCSI can be much faster than any Z II, Z III, or subsequently PCI card - it has direct access to the accelerator RAM w/o being slowed down by a slow bus connection.

PCI is a slight exception as DMA into (video) RAM on the PCI bus can even be much faster even - but the CPU would need to use the slow bus to get at it.

Plus, you won't be able to boot from any PCI SCSI HBA.

I know, I know.

It's definitely not with a light heart that I would even want to do it. But I don't want to downclock a perfectly fine 77MHz 060 either.

[ChaosLord]

You should think about this first.

I was told that if you add memory to the SCSI kit board that you must then slow your RAM speed down by 10ns to 70ns.  In your case it would be slowed down by 20ns.

Maybe I was told incorrectly.  But it made sense when they told me that RAM on the Addon board is further away and the CPU can't drive it as fast.

When I say "slow down your RAM speed", I was told there is only one speed setting for the whole Blizzard 1260.  So u would be throwing away ur expensive 50ns SIMM on the mainboard and the one on the addon board.

But don't worry, if u give me some time I will buy ur SIMM from u so it doesn't go to waste.  As long as it works.

[Zac67]

I see - you want the SCSI module, but without the SCSI...

Have you tried simply removing the 27C256 EPROM? Won't actually disable the hardware but probably what you want.

ChaosLord has a point - the sandwiched board adds length and noise to the RAM traces - you'll need to test the memory very well if you'd like to trust it.

[Blinx123]

You should think about this first.

I was told that if you add memory to the SCSI kit board that you must then slow your RAM speed down by 10ns to 70ns.  In your case it would be slowed down by 20ns.

Maybe I was told incorrectly.  But it made sense when they told me that RAM on the Addon board is further away and the CPU can't drive it as fast.

When I say "slow down your RAM speed", I was told there is only one speed setting for the whole Blizzard 1260.  So u would be throwing away ur expensive 50ns SIMM on the mainboard and the one on the addon board.

But don't worry, if u give me some time I will buy ur SIMM from u so it doesn't go to waste.  As long as it works.

This is only correct for the Blizzard 1230s, actually (the thing about having to set a switch to 70ns).

Still. You're correct. I'll probably need to slow it down a fair bit.
Could've saved some serious money (20 euros) there, I suppose

Would it be a valuable asset, should I ever feel the urge to upgrade to a Blizzard PPC?