UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Gemini 80-Bus System

JohnBHanson · 24th Sep 2020, 6:38 pm

I would *almost* bet money that the problem with booting without the xebec controller is that command 0x0c (Init Drive Characteristics) is not implemented on your SCSI2SD card.

see xbeaver.c gemini_scsi.c change on 14/9/2019 for details.

perhaps you can modify the code in your SCSI2SD card to implement this command. It does not have to do anything just swallow its parameters and then return a good result status as per other scsi commands.

The reason it is there is that the xebec needs to know the geometry of the disk connected to it. SCSI access is done by logical block number and the xebec must translate this to cylinder/head/sector and hence needs this
infomation. A native scsi disk already knows this as the interface is native to the disk.

24th Sep 2020, 6:38 pm	#405
JohnBHanson Heptode Join Date: Aug 2009 Location: Worthing, Sussex, UK. Posts: 661	Re: Gemini 80-Bus System I would almost bet money that the problem with booting without the xebec controller is that command 0x0c (Init Drive Characteristics) is not implemented on your SCSI2SD card. see xbeaver.c gemini_scsi.c change on 14/9/2019 for details. perhaps you can modify the code in your SCSI2SD card to implement this command. It does not have to do anything just swallow its parameters and then return a good result status as per other scsi commands. The reason it is there is that the xebec needs to know the geometry of the disk connected to it. SCSI access is done by logical block number and the xebec must translate this to cylinder/head/sector and hence needs this infomation. A native scsi disk already knows this as the interface is native to the disk. Last edited by JohnBHanson; 24th Sep 2020 at 6:44 pm.