Classic IDE DMA possible?

[mboehmer_e3b]

Hi,

> I'm looking at the Zorro 3 specs and to me it looks like
> there is the ability to do DMA access of up to 50 MB/s non
> burst.

Zorro III DMA is tricky, as both last Buster versions (rev 9 and rev11) have quite some quirks in it which must be taken care of. It is possible, but needs quite some development effort.

Moreover the Zorro III burst modes (/MTACK and /MTCR signals) do not work, and even if they would - most Zorro III cards, and CPU cards on A3000 / A4000 do not support burst, which is limiting bandwith anyhow.

Michael

[mboehmer_e3b]

> I was sure my Fastlane Z3 did burst and it can sustain
> 11MB/sec no problem. I know the hypermemory card used
> burst modes.

Don't mix up memory burst on the card itself and burst access on the Zorro III side. The first one is up to the designer and completely decoupled from the bus interface itself.

Burst mode on Zorro III (using /MTACK and /MTCR) does not really work. If it worked you could do one Zorro III cycle and access 64 longwords, doing only one Zorro III address phase and 64 data phases.

> Now i'm thinking, I haven't seen any 100Mbit ethernet
> cards. I wonder why burst isn't working!

Well, 100MBit on Zorro III is possible - believe me :-)

Michael