Amiga.org

Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: sim085 on July 15, 2009, 09:11:36 AM

Title: CF Mode (some surprises)
Post by: sim085 on July 15, 2009, 09:11:36 AM

Hello,

While building my CF mod for the GVP HD8+ I came across various problems and some surprises. One of the surprises was the following:

When my ACard AEC 7720U arrived I only had a molex cable that could split power from PC Power to PC Power/Floppy. The ACard AEC 7720U takes power from a floppy connector and so did my IDE -> CF card. I decided to connect that floppy connector to the 7720U and leave the IDE -> CF card without any power.

... to my surprise everything worked fine! I was under the impression that for DMA support the IDE -> CF card would need floppy power as well.

I ordered another cable (PC power to floppy / floppy) connected everything and I must say there was zero gain in speed!

So does it really matter?

Regards,
Sim085

Title: Re: CF Mode (some surprises)
Post by: Zac67 on July 15, 2009, 09:55:36 PM

Hmm... Actually, CF isn't anything else than (E)IDE with an alternative connector. The CF to IDE adaptor is just mechanical, so it's surprising that there's a power connector at all.
I've never used such an adaptor, so this is pure theory. ;)

Title: Re: CF Mode (some surprises)
Post by: pyrre on July 15, 2009, 10:04:46 PM

I have CF/IDE adapters as wel. and some of them has floppy power connectors. But they do not have traces leading out from the connector to other areas on the card...
The adapter(S) i have powers fine from the IDE bus alone. However. the SD/IDE adapter i have needs floppy power...

Title: Re: CF Mode (some surprises)
Post by: Daedalus on July 16, 2009, 08:43:46 AM

SD<->IDE is an active conversion, like IDE<->SCSI, and so some electronics are required for it to happen. It's possible the power connection is there just in case the IDE port the adaptor is connected to doesn't provide enough power - it's possible that it's limited as any hard drive will have a separate +5V supply. I doubt very much it would make the difference between DMA and non-DMA, that'd be more down to the controller and what the card supports than whether it has auxiliary power connected.

Title: Re: CF Mod (some surprises)
Post by: sim085 on July 16, 2009, 11:49:51 AM

Quote from: Daedalus;515820

I doubt very much it would make the difference between DMA and non-DMA, that'd be more down to the controller and what the card supports than whether it has auxiliary power connected.

Thank you :) That is good to know.