Answer to the second question is simple: 680x0 asm doesn't support byte operations on address registers.

Basically there needs to a terminator on the external SCSI port or last device and it needs to be the ACTIVE type not passive. Also SCSI ID's must not conflict. IIRC the Motherboard header is SCSI ID 7.

You will certainly run amuck if you are running HDTOOLBOX from a Workbench 1.3 boot sequence. Nothing fitting as far as libraries and SETPATCH will be installed.
For OCS Workbench 1.3, HDInstall tools (HDINST.lha on Aminet. Was formerly an Alpha Data HDD tool) or a propriety installer like the GVP releases are known to work.

In the WB 3.1 startup-sequence; the command C:Setpach QUIET or other variants, patches ROM with certain updates in the DEVS folder. scsi.device is often one of these. Depending on circumstance and configuration an update patch is the thing needed to get the system working.

Of course there could be a physical issue with the HDD like stuck heads. Some have tried a light hit with a hammer to the HDD to loosen them, others more tech savvy dissasemble to drive and repair or replace.

I've been trying to find some side-by-side comparisons of the A1200NG to other stand alone systems.  The info I first found (can't find it now  ) put the A1200NG way below other offerings, but with the proposed Turbo card, it will be much faster than anything else.

Has anyone put together such a comparison?

https://www.amigaretro.com/index.php?page=Vampire-V4SA

Standalone Vampire V4 - 181.5 Mips

My "Boosted" A1200 NG using the same sysinfo. 270Mips mips as attatched.
Unboosted it is about 210-215 mips.

Sysinfo 3x too old.

270 is more than 181 last I checked.

Ok, I used to use my A600GS a lot, often just for playing some A500/A1200 games from ADF (sometimes WHDLoad) but there are games that are not very demanding BUT will not run smooth on the A600GS and so I´ve put it away some time ago. But let me explain ...

Two examples :

The Lost Pixel : https://amiga-factory.itch.io/projectlp
Casltevania AGA : https://danteretrodev.itch.io/akumajou-dracula-aga

Both have slowdowns, The Lost Pixel got stuttering music (like hell) even in the menu and the game is unplayable slow ...

Hi SkulleateR and others in the thread,

Thanks for all the research and reporting your various settings. I am wondering if you have had any success with these titles? I just got a A1200NG and downloaded the latest version of CastlevaniaAGA (October 31, 2025) I am running the .HDF and am getting slowdowns especially on the first level. Creeping Me Out Hex Night is experiencing slowdowns as well. I am currently trying Demo 2. https://mixelslab.itch.io/creeping-me-out-hex-night I notice all these games were made with Scorpion Engine. Could there be something with Scorpion engine and A600GS/A1200NG? They run smoothly on my other emulation devices. I have tried them via AmiBench, the provided .HDF, and my own vanilla OS3.1 .HDF install. Let me know if you got any of these working smoothly. I will keep trying as well and report back if I get them working properly. Another weird one is that the classic demo State of the Art by Spaceballs slows down in a couple of parts as well. I am running that one from ADF in the launcher. Thanks so much!

Thank you, this is helpful background information.

I understand about the mismatched KS vs WB, but it remains that with KS 3.1 and WB 3.1 (Sorry, I had said 3.2), WB consistently crashes at start up if the drive is attached. This would
seem to preclude much in the way of software investigation/configuration. The KS 3.1 plus WB 1.3 combo at least let me verify the drive, even if it is "wrong". Maybe investigation in this
direction is ultimately pointless, but I mention it for completeness.

Anyway, the drive itself is an internal Quantum 525S. Maybe it's a replacement, who knows. I have verified its termination jumper is set. Also supplied with the machine are an external SCSI scanner and CD drive, so who knows what the full setup of this machine was previously. I connected those yesterday to see if the effect was the same, and it was.

As noted in this thread:

https://eab.abime.net/showthread.php?t=113367

"This is the 100000000th thread about this topic"

In fact, although there are lots of A3000 motherboard pictures, I can't find a good one of the termination resistors. I was waiting until my coin cell holder (still not shipped!) came before stripping the machine down and taking a proper look.

Perhaps the drive is just faulty, or there's some termination configuration I need to try, or some other incantation. I welcome suggestions on other things to look at.