RE: 90x0, was: New user

RE: 90x0, was: New user

Date: Mon, 20 Apr 2009 07:47:44 +0200
Message-ID: <>
Hallo André,

> Why don't you just try to replace the SASI-to-MFM-plus-HD part
> with a SCSI disk, and modify the kernel appropriately 
> (if even necessary)?

1) Having had a good look at your designs, IMHO a SCSI interface needs a lot more signals then the SASI interface provides. Can SCSI operate W/O this parity thing? If not, we already have a problem.
2) You automated the data transfer but the 90x0 still uses bit-banging: a 6522 takes care of the hand-shake signals AND the data transfer.  
3) I disassembled the ROMs but understanding the code is something else. And I have only a vague idea what the SASI-part code does; not only the code handling the SASI interface itself but I also don't understand when what code is called by the DOS-part.

If I manage to resolve 3), I for myself will go for an IDE harddisk. Just one 74LS139 needed to connect it. And I have plenty of them laying around, something I cannot say from SCSI disks. And the biggest 50-pins one is just 800 MB. The bigger disk are all SCSI-II IMHO, this D-connector look-a-like connector. 

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