Zorro DMA vs Accel. DMA: Cyberscsi vs A4091

[Jose]

So, I was thinking:
1- The onboard scsi of the A4000T and the A4091 scsi controlers are reported to be faster then the Cyberscsi module of the Cyberstorm MkII or other processor card add ons.
2- Yet the 4091 uses the ZIII bus, which means that it will be in direct competition with say a Gfx card if you want to do dma transfers from accelerator memory to video memory (or is that not possible ?).

This means that if one wants to run a high frame rate / high res / true color anim, a Cyberscsi based system will still be faster since it won't be using the ZIII bus at all.

Is this correct, or no difference in practice ?

[Jose]

This is a big mess...
PIV ZIII transfers are around 14MB/s IIRC, Cybervision64 16MB/s and the 3d model of it 6MB/s.
I'm thinking about keeping the PIV so it should be around 20MB ZIII bandwidth with the disk transfers (not that there will probably be any software taking advantage of it but it would be fun to program for....
On the other hand, I've been considering selling the 4000T for a while, but since my MKII (recently bought from eBay) doesn't have the Cyberscsi module I don't know.
Specially since the MKII is reported to not overclock well with the scsi module.
I've seen an old post by Pasha saying there is a version of the scsi module that tolerates overclocking but I've yet to see a report with an 80Mhz MkII with working scsi. The A4000T would allow that easily, getting an 4091 for the 4000D will make it too hot and with no space inside...
But then A4091 controler (same one on the 4000T) doesn't work with a DMA enabled Deneb...

Decisions, anyone seen a working Cyberscsi module at 80Mhz ?

[Jose]

@doctorq

Thanks a lot for posting that, looks like I'll have to use the 4000T or get an A4091. Shame that it won't work with a Deneb...

[Jose]

@doctorq
Have you tried just various oscillators ? It could be a timing issue. Also, do you have 70ns ram ? If so ram could be the limiting factor.

@Damion
Sounds interesting (Z2 vs Z3), but you didn't say what video cards / processor cards you have on them...

[Jose]

@Zac67

I could put back a Buster9, which supports more than 1 DMA device but it doesn't work with the A4091 (it's what they say but I also remember having an A4091 working with Buster9 before that and it worked fine!?) and my Busters are both rev. 11 and soldered on both machines:(. Funny, I payed Castellen to solder the rev. 11 in the 4000D and I think he asked me if I wanted to put a socket, to which I said no, for what...

The only other solution would be getting a FastLane or a 4098 from GVP. I don't know if the GVP works with Buster9 but the FastLane does. On the other hand Fastlanes cost a fortune on eBay.

[Jose]

@Ami_GFX

I'd say get one of those SCSI to IDE adapters, they're cheaper nowdays and make the HD so much faster than IDE and specially with small overhead.
Ah, ok 4008, I was think about the 4098...

[Jose]

BTW, a FastLane or 4098 or DKB, whatever, probably would have problems too, some of them might be DMA masters. Anyone has a list of cards which are DMA masters, must be a small one...