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General Category => Technical Support => Topic started by: GUNHED on 18:10, 08 March 21

Title: Dukes M4 card and the Dobbertin HD20 hard disc
Post by: GUNHED on 18:10, 08 March 21
Well, I love the Dobbertin HD20 hard-disc since the day I bought it (used). It has so much software support, just great.

Also I do love Dukes neat M4 card. Which is awesome.

However, I have trouble there...

The Dobbertin HD20 controller provides X-DDOS at ROM position 6.
Therefore I put X-DDOS in ROM 6 of the M4 card too and moved the M4 ROM to position 5.

The 6128plus is fine with the M4 alone, but as soon as I also connect the HD20 controller there are problems: The computer crashes when initializing the ROMs. What could be the reason?
Title: Re: Dukes M4 card and the Dobbertin HD20 hard disc
Post by: Duke on 19:41, 08 March 21
@GUNHED (https://www.cpcwiki.eu/forum/index.php?action=profile;u=2029)
How about putting M4 in 7 or 8?

And what I/O address does the HD20 use? Maybe it doesnt do full address decoding so there is overlaps?
Title: Re: Dukes M4 card and the Dobbertin HD20 hard disc
Post by: GUNHED on 20:17, 09 March 21
The problem seems to be to have the identical ROM image two time on the same position. There was no problem with other ROM cards I tested, so it was unexpected. I will try to have a closer look, but may not get much more information.


About the HD20 here is a document I did a while ago (actually for emulating the HD20 with the M4, which would solve all problems). But now just for your information...



Title: Re: Dukes M4 card and the Dobbertin HD20 hard disc
Post by: Duke on 12:52, 10 March 21
About the HD20 here is a document I did a while ago (actually for emulating the HD20 with the M4, which would solve all problems). But now just for your information...

Thanks. Looks very well documented, good job!
Title: Re: Dukes M4 card and the Dobbertin HD20 hard disc
Post by: GUNHED on 14:59, 10 March 21
Thanks. Looks very well documented, good job!
Thanks. I will try to expand this document.

About the HD20 problems: Little further investigation did result in this: It seems to be needed to have hardware ("coming before", means between CPC and HD20 controller) supplied with enough power. I don't have an oscilloscope here, but IMHO there could be a competition between signals.

FlashGordon between CPC and HD20 works, M4 card not. The integrated ROM of the HD20 controller may be mirrored every 16 ROMs, this seems to be problematic. Have to do more tests....  :)