Search found 522 matches

by Diminished
Tue Sep 01, 2020 11:02 am
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

Marvellous! I would expect to see a YIELD kind of opcode at the end of a routine. Yeah, I now notice that's actually explicit in the patent. Screenshot 2020-09-01 at 11.02.10.png edit: one more thing: Screenshot 2020-09-01 at 11.34.07.png So in multi-segment routines, you might expect some instruct...
by Diminished
Tue Sep 01, 2020 10:51 am
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

Haha, nice. You boys have been busy. The same thought occurred to me -- that it works a bit like a set of ISRs? I've encountered no mention of multiple stacks either. Maybe one "segment" means a short callback routine which is run quickly in one shot, and which is obliged to leave the stack empty wh...
by Diminished
Tue Sep 01, 2020 1:05 am
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

Made some notes on Fig. 1 in the patent while trying to get my head round it. Talking mainly about the byte processor rather than the bit processor here. 8271-patent-fig-1.jpg The main thing I took away is that the PLA address generator -- which is used to load the program counter with a new value w...
by Diminished
Mon Aug 31, 2020 5:44 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

guesser wrote:
Mon Aug 31, 2020 5:34 pm
Right, I've added "alpha", with a small correction where something was connected that shouldn't be again.
Whereabouts?
by Diminished
Mon Aug 31, 2020 1:14 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

Another one I did a couple of days ago.
alpha.zip
(7.59 KiB) Downloaded 7 times
by Diminished
Mon Aug 31, 2020 12:56 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

Here's that long path I traced yesterday.
long1.zip
(33.64 KiB) Downloaded 6 times
by Diminished
Mon Aug 31, 2020 12:39 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

Another update from Sean: These are definitely worth having, although he's right, they're still not perfect, sadly. It's hard to visualise exactly how he suggests cutting the chip. It's slightly frustrating because I have one of these in the cupboard, which strikes me as the sort of thing that migh...
by Diminished
Mon Aug 31, 2020 11:35 am
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

Noteworthy: "One function [of the byte-level processor] is a mode used to simplify chip testing" This is actually explicitly mentioned in the 8273 sheet , but not in the 8271 one. (One one). Very first page, in the register block. Here's a thing. The decoder for the narrower of the two ROMs at bott...
by Diminished
Mon Aug 31, 2020 4:07 am
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

Man, this document is amazing. Two ALUs. >_< The real irony is that I think everyone was right about the thing's nature. I said 8-bit bus and a state machine. Others suggested a microcontroller. I don't think any of us thought it would have both of those and a couple of kitchen sinks on-die as well....
by Diminished
Mon Aug 31, 2020 3:55 am
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

Ok, I have a confession to make -- I did chat to Ken (http://righto.com blog owner) and we exchanged some notes and ideas. And then Ken found a couple of extremely enlightening documents, which are attached: - A paper abstract from a 1977 conference. You will recognize the photo in it. - A patent a...
by Diminished
Mon Aug 31, 2020 3:54 am
Forum: 8-bit acorn software: classic games
Topic: Repton (1, the original) disc variants found
Replies: 7
Views: 682

Re: Repton (1, the original) disc variants found

Yeah the way I've tackled this sort of thing in the past has been to do something like ... work out where the game's entrypoint is, and then breakpoint it. Provided it's the same in different versions, you can then just dump 32K of RAM from the debugger (I had to add a command to b-em's debugger to ...
by Diminished
Sun Aug 30, 2020 10:41 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

I wonder if Olivetti ever ended up using it for anything. This might be everything, finally: phew.jpg It touches a few interesting things, like the vertically arranged 8-block (registers?) in the south, and the big ROM thing in the far north-east. It might be part of the clock (maybe there's one or ...
by Diminished
Sun Aug 30, 2020 9:04 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

BigEd wrote:
Sun Aug 30, 2020 8:55 pm
...
Brilliant as always, thanks.
by Diminished
Sun Aug 30, 2020 8:46 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

Need an opinion on this. unsure.jpg unsure2.jpg What I think I have here is a resistor. The white arrow is a horizontal metal track. I think this is a via going into diffusion, and then there's another via up to the polysilicon, which heads south? Is that right? Incidentally, I'm currently dealing w...
by Diminished
Sun Aug 30, 2020 8:10 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

huh... I thought the connection I decided wasn't real was on the polysilicon... Now I'm confused lol. Edit: ah yes, I see, what you're pointing to is indeed fine, but it's not connected to the poly trace coming down the outside of the die. There's just a gate that goes near to it. Yeah, I gotcha. P...
by Diminished
Sun Aug 30, 2020 7:26 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

guesser wrote:
Sun Aug 30, 2020 6:15 pm
There isn't a connection to SELECT0
There isn't?
select0_what_1.jpg
select0_what_2.jpg
What does the metal connect to, then? It clearly isn't the polysilicon underneath.
by Diminished
Sun Aug 30, 2020 4:02 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

8273 datasheet is here (to save you from the horrors of dodgy datasheet sites): https://drive.google.com/file/d/10QiA8pZS4w4snQAhvm6CAOw0IXQI6z7E/view?usp=sharing I glanced at it. I'll have a proper look at some point. Very Interesting! :D Did you spot my earlier post ? There's another SVG there for...
by Diminished
Sun Aug 30, 2020 3:48 pm
Forum: 8-bit acorn software: classic games
Topic: BBC Elite source, now fully documented and explained
Replies: 75
Views: 3272

Re: BBC Elite source, now fully documented and explained

Sounds wonderful. I'll be sure to have a good peruse when I'm not tediously vectorising disc controller die shots. :/
by Diminished
Sun Aug 30, 2020 12:24 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

This has been my feeling since we saw the first die shot Actually.... just found some really fascinating evidence. Head over to http://archive.computerhistory.org/resources/text/Oral_History/Intel_8080/102658123.05.01.pdf and read page 16 and 17. It's a couple of early Intel employees who worked on...
by Diminished
Sun Aug 30, 2020 9:32 am
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

I doubt this FDC is based on a standard MCU. No FDC that I know is based on a standard MCU, they are all full custom. They do use microcode, as seen on the die. But microcode structure is quite different from standard firmware. I'm afraid chances are you are wasting your time trying to understand t...
by Diminished
Sat Aug 29, 2020 10:19 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

One more I traced earlier. This one is interesting because it seems to route an output pad back internally to the chip (SELECT0), and it appears to gate some pretty interesting things. I can't see anything obviously similar for SELECT1, but perhaps they're strict inverses of one another, in which ca...
by Diminished
Sat Aug 29, 2020 9:04 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

Here are the exported SVGs of bits 8 and 9. I'm working at 50% (133 MP) instead of 100% now, so you'll have to scale them accordingly.
page_paths.zip
(4.26 KiB) Downloaded 7 times

Viel Spaß!
by Diminished
Sat Aug 29, 2020 8:54 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

That's a metal to diffusion via with a couple of gates around it like the connections to the bus from the output of the ROM I finished tracing out last night. Ah yes, it's obvious now I look at it again. I've been staring at this too long. :shock: Thank you. The diffusion silicon is presumably conn...
by Diminished
Sat Aug 29, 2020 8:16 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

Can anyone tell me what the green line (which is metal) is directly connected to here?
nicht_verstehen_1.jpg
nicht_verstehen_1.jpg (11.72 KiB) Viewed 483 times
nicht_verstehen_2.jpg
nicht_verstehen_2.jpg (10.26 KiB) Viewed 483 times
Is it the region to the right of its via, or the region to the left of it?
by Diminished
Sat Aug 29, 2020 8:02 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

guesser wrote:
Sat Aug 29, 2020 8:00 pm
Also the address decoder is plainly a straight binary count even if the lines were scrambled up, which they don't appear to be.
Well, I was thinking the big ROM contents would be transposed too, but I agree it doesn't make much sense to do it.
by Diminished
Sat Aug 29, 2020 7:40 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller craziness -- do not try this at home!

dp11 wrote:
Sat Aug 29, 2020 7:34 pm
jumps can have all bits changing so don't actually buy you anything.
Drat.
by Diminished
Sat Aug 29, 2020 7:29 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

Hmm

Has anyone tried Gray code, in which no more than one bit changes at a time? There are actually compelling reasons why that might be beneficial here (no skew glitches).

There's an automatic Gray code generator here if you want to play with it.
by Diminished
Fri Aug 28, 2020 8:46 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

Just a bit more waffle: Here are the obviously regular structures on the die that I've found are connected to that 8-bit bus -- lots of 'em. Pretty much all of these connect in the same bit order (with respect to their layout). bus_all_structures.jpg The fact that the bus lines terminate in the top-...
by Diminished
Fri Aug 28, 2020 8:26 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller de-cap and craziness -- do not try this at home!

Right now I wonder if the address bits need swizzling somehow. I messed about with this idea last night, but the difficulty is finding a way of doing it which doesn't overflow the row decoder. We only have 108 rows -- it's not a power of two. Ditto inverting the bits -- your first read is off the e...
by Diminished
Fri Aug 28, 2020 2:12 am
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15527

Re: 8271 disc controller craziness -- do not try this at home!

Try this: https://siliconpr0n.org/wiki/doku.php?id=rom:mask I don't know if this is exactly how this works, since this is an NMOS process and I think the schematic examples there are CMOS ones. I didn't show any ROM in my picture but the one earlier in this page that guesser posted shows the individ...

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