Who's the /BOSS on the Amiga 2000 ?

 I slipped and bought a TF536 to put into my Amiga 2000. TL;DR is it's now running, but it took a bit of fiddling to get there. When I was last getting it going I noticed it didn't like any Zorro-II RAM in there, so I simply disabled it (it wouldn't do much) and left it alone. The storage card I'm using (a GVP SCSI job) doesn't do DMA to Zorro-II RAM - it does DMA to/from a 64k IO/RAM window which then the driver memcpy()'s out.

Whacking it in with the CPU riser I got from amigastore.eu booted up fine as long as no other RAM cards were installed.

If I installed my storage card or any zorro-II RAM cards it just hung. Not fun.

So then I thought, wait a sec. It's going into the CPU expansion slot, not the CPU socket. And there's this thing called /BOSS which accelerator cards in the CPU expansion slot should assert if they want the DMA and some other signals routed to them rather than the main CPU socket.

So, I grabbed a different one.

This one has a jumper for /BOSS to keep it enabled, and also has the FC0..FC2 pins (indicating the CPU state) also routed.

I plugged this in and bam.

(note I didn't leave the 2MB RAM enabled on the storage card after this test; until I'm ready to screw around with programming stuff that explicitly wants to test Zorro-II/Zorro-III space RAM, I'll leave it off.)

I also tested it with an 8MB Zorro-II RAM expansion (the ZoRAM card that's available on the internet) and it also works fine.

Anyway TL;DR is - don't forget to ensure your accelerator card installation on an Amiga 2000 has /BOSS asserted, or a bunch of DMA/Zorro-II lines won't get routed to the CPU expansion slot and things won't work right.

damnit i slipped and (mostly) built an amiga 500

EDIT - the original article has an image of the PCB with the floppy power connector mounted the WRONG WAY. 

This is the INCORRECT WAY. Do NOT do it this way!

TL;DR - I'm half way through building an Amiga 500+ replica. The goal:

• New PCB
• New clear case
• Actual floppy drive!
• TF534 Accelerator, yes I am interested in FPU stuff for reasons and yes I'm sad about the 4MB of RAM but I'll make do - terriblefire does a great job designing/building/debugging these accelerators and I'm glad they exist!
• ECS Denise, also for reasons
• 2MB chip RAM and some slow RAM too because again why not
• 3.x ROMs

The challenges!

• I need a keyboard for it, but my "donor" machines, like my "donor radios", all now work. Hilarious.
• The Amiga 500+ board wasn't well documented for assembly, until I looked. Closer.
• Well, the 8375 Agnus I acquired is a PAL one, so I guess I'm building a PAL Amiga 500+. (Which is fine as you can switch it in software after boot, but STILL.)
• Oh yeah, floppy drives. Ugh.

Ok, so the PCB. I picked it up from https://www.tindie.com/products/bobsbits/a500-amiga-500-replica-pcb/ . There's a link with the component list, and I got them all with some hunting around. I wish I had a "dead-ish" donor Amiga 500 of suitable vintage to grab parts from, but again, all my machines now work. Ha.

Here's it assembled. Well, mostly.

I still have some connectors and the RTC to add. Yes, it's a 2.x workbench ROM. Yes, it boots to ROM fine.

Now, what do I do about the jumpers? The instructions don't have the Amiga 500+ rev8 PCB jumper descriptions. Ok, they're in the service manuals. And yeah I can read the schematic, but I wanted to be lazy.

Ok, so I started to look at it. I definitely wanted the 1MB/2MB option. I wanted the expansion RAM to show up in chip RAM to start with. Ok, ok. But, guess what. The PCB has them already kinda done.

Here, look closely.

JP3 is already done for us. (For 1MB/2MB I need to have them horizontally jumpered, not vertically.)

And for JP2:

It turns out the two bottom pins are already joined. I'd have to cut the track to start using the expansion RAM slot as slow RAM (in $C00000) or if/when I fit a Gary Adapter / RAM expansion add-on.

Finally, the case is here and the TF534 is installed and boots up to ROM fine.

I'll finish the installation once the sockets arrive - and yes I may go and borrow my rev5 amiga 500 keyboard and Gotek floppy drive emulator until I get suitable replacements. Or, maybe just design an Amiga 500 keyboard drop-in replacement with cheap cherry MX style switches. Why not.