Search found 522 matches

by Diminished
Sun Sep 20, 2020 3:02 pm
Forum: past acorn preservation team sessions
Topic: Acorn Preservation Team meeting #1, Sunday 20th September 2020, 6:30pm - 9:30pm
Replies: 17
Views: 1011

Re: Acorn Preservation Team meeting #1, Sunday 20th September 2020, 6:30pm - 9:30pm

It struck me that some of what this group is tackling is rather like what museums have to do. Here's some advice from The National Archives including a spreadsheet listing available software. I note they mention Collections Management Systems which is another meaning of CMS. They also mention Digit...
by Diminished
Sun Sep 20, 2020 1:56 pm
Forum: past acorn preservation team sessions
Topic: Acorn Preservation Team meeting #1, Sunday 20th September 2020, 6:30pm - 9:30pm
Replies: 17
Views: 1011

Re: Acorn Preservation Team meeting #1, Sunday 20th September 2020, 6:30pm - 9:30pm

all online and offline archives are backed up/shared/mirrored* ... publicly if possible, or at least restricted to known, trusted archivists if possible. *Not just file archives/site leeches etc, functioning mirrors where possble. There are certain advantages to using BitTorrent for this. There's a...
by Diminished
Sat Sep 19, 2020 1:11 pm
Forum: 8-bit acorn hardware
Topic: I need to learn
Replies: 7
Views: 415

Re: I need to learn

I've obviously no idea what you know already, but just off the top of my head I guess you'd probably need to learn more or less the following things (in approximately this order): - bitwise boolean logic - how numbers are represented in binary, including negative numbers and two's complement, maybe ...
by Diminished
Thu Sep 17, 2020 10:47 am
Forum: 8-bit acorn hardware
Topic: [SOLVED] Elementary question about the audio amp on a BBC B
Replies: 2
Views: 155

Re: Elementary question about the audio amp on a BBC B

IIRC the audio amp is an LM386. Data sheet here. Seems to suggest 4 to 32 ohms is an acceptable range.
by Diminished
Wed Sep 16, 2020 5:35 pm
Forum: new projects and releases: demoscene
Topic: Ray tracing in a tweet
Replies: 4
Views: 336

Re: Ray tracing in a tweet

Classy.

Is the floor meant to be curved?
by Diminished
Tue Sep 15, 2020 7:45 pm
Forum: stardot FORUM
Topic: Unicode déjà vu (not important)
Replies: 6
Views: 1019

Re: Unicode déjà vu (not important)

There was a big forum migration (maybe this one ?) which left a bit of Unicode wreckage, which was then, I think, found and cleaned up. But just possibly only post texts were fixed, not title texts. Ah yes, that would do it. If you searched for Ã, maybe you could find all of them, but the search fu...
by Diminished
Tue Sep 15, 2020 7:43 pm
Forum: introduce yourself
Topic: Hi from London!
Replies: 8
Views: 249

Re: Hi from London!

Perhaps now you could graduate to writing rudimentary programs in assembler to print rude words on the screen?

Hello!
by Diminished
Tue Sep 15, 2020 7:34 pm
Forum: stardot FORUM
Topic: Unicode déjà vu (not important)
Replies: 6
Views: 1019

Re: Unicode déjà vu (not important)

e-acute is Unicode code point U00e9 ... If you encode it three times, you get an eight-byte UTF-8 sequence: Unicode code points | UTF8 ----------------------------------------|------------ 0xe9 -> 0xc3 0xa9 0xc3 0xa9 -> 0xc3 0x83 0xc2 0xa9 0xc3 0x83 0xc2 0xa9 -> 0xc3 0x83 0xc2 0x83 0xc3 0x82 0xc2 0x...
by Diminished
Tue Sep 15, 2020 6:55 pm
Forum: stardot FORUM
Topic: Unicode déjà vu (not important)
Replies: 6
Views: 1019

Re: Unicode déjà vu (not important)

I think it's being UTF-8 encoded ... three times, instead of just once?!
by Diminished
Mon Sep 14, 2020 7:53 pm
Forum: trickysoft (new bbc micro games)
Topic: Canyon Bomber emulator/source code port without the source
Replies: 3
Views: 202

Re: Canyon Bomber emulator/source code port without the source

Good stuff trickster.

What was the original machine's clockspeed? How about the frame rate? Did you have any 50/60 Hz nonsense to deal with?
by Diminished
Sat Sep 12, 2020 2:43 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15532

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

Checked my 8273 program ROM dump against the new photograph and found six errors. I've corrected my previous post with the disassembly . The changes to the listing are as follows: 0ca 5b ff d2 BNE I11, #0xff, 0x0d2 0cd aa ??? 0ce 9c 0f AND A, #0xf -0d0 89 af BPL 0x0af +0d0 8b af BNZ 0x0af 0d2 98 0f ...
by Diminished
Sat Sep 12, 2020 10:31 am
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15532

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

Sean wasn't kidding when he said he chipped one of those 8273 dies. 8273acid_chip_lolz.jpg Anyway, he picked the correct corner to chip and the tables are readable on this sample, so I was able to complete the (preliminary) job on the 8273. EDIT: there were six errors in this transcription, hopefull...
by Diminished
Fri Sep 11, 2020 7:48 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15532

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

(Here's the trashy disassembler I scraped together to list the 8273 program. Basically useless but hey.) <?php define("OPARG_IMM", 1); define("OPARG_ABS", 2); define("OPARG_UNK", 3); define("OPARG_IMM_NOCOMMA", 4); define("OPARG_ABS_NOCOMMA", 5); //$s = file_get_contents("my8271.bin"); $argv = $_SER...
by Diminished
Fri Sep 11, 2020 9:26 am
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15532

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

Yeah, I'm disappointed, honestly. I was hoping to find some opcodes not used by the other chip, but I don't think there are any. (edit: actually not true!)

Probably time I went back to doing something else.
by Diminished
Thu Sep 10, 2020 11:35 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15532

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

Quick and dirty bash at the 8273. I was hoping there might be an EF in here, but it doesn't look like there is. ; entrypoint: 000 04 SEL RB 4 001 f0 08 MOV I0, #0x8 003 f4 00 MOV I4, #0x0 005 f5 ff MOV I5, #0xff 007 b8 00 ???, #0x0 009 b9 00 ???, #0x0 00b bb 00 ???, #0x0 00d bc 01 ???, #0x1 00f c8 f...
by Diminished
Thu Sep 10, 2020 8:32 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15532

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

This should be a pretty accurate rendition of the 8273's entrypoints -- the output table was much easier to read than the input one. 0x30 0x3a 0x27 0x1a8 0x10c 0x1a8 0x119 0x11f 0x120 0x1a2 0x197 0x19b 0x173 0x1c3 0x180 0x308 0x299 0x2e3 0x2f2 0x332 0x2ff 0x302 0x305 0x2fc 0x356 0x340 0x91 0x9a 0x31...
by Diminished
Thu Sep 10, 2020 7:00 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15532

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

In less groundbreaking news, I appear now to have code which can successfully decode the inputs to the address PLA from a marked-up image of the bits, and handle the don't-cares gracefully (slightly more annoying than I expected), so I'm set up for if and when we get a better 8273 pic. The good news...
by Diminished
Thu Sep 10, 2020 6:22 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15532

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

Fascinating.

Might be better just to forget the patent and pick new names.
by Diminished
Thu Sep 10, 2020 5:48 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15532

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

Register banks are selected by opcodes $00...$0F. Each bank is 8 registers, so opcode $02 would suggest a base register of $10. I see! Now I said there were 32 internal registers, but this is literally only half the story! Because if you select register bank 4 (a base of $20), you get access to I/O...
by Diminished
Thu Sep 10, 2020 2:40 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15532

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

How do the registers work, Rich? I see a lot of MOV Ix type stuff, but then you have references to Rx in the comments.

What about the register banks? What's the dealio with those?

(I can wait for answers, just as long as someone writes this stuff up properly afterwards. :D)
by Diminished
Thu Sep 10, 2020 1:27 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15532

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

Rich Talbot-Watkins wrote:
Thu Sep 10, 2020 11:50 am
Perhaps that's not what you're talking about though.
No, it wasn't, but it's OK ... I started typing up a post to explain what I meant, and in doing so I realised I'd misunderstood something (specifically, the don't-care combinations in the PC decoder input).
by Diminished
Thu Sep 10, 2020 11:44 am
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15532

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

Hey, guesser, you know the program counter table? You seemed to read what turned out to be the program counter values out of the right-hand side of each cell, am I right? What's on the left-hand side of each cell? Are they likely to be another set of PC values in there? I'm not sure why there would...
by Diminished
Thu Sep 10, 2020 11:06 am
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15532

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

Ah, so that unknown 2-bit ID was a register bank? I've tried to mark up the program counter table for the 8273, but it's basically impossible to achieve any sort of accuracy at all with the muck on the current photo, so I don't think it's even worth bothering at this stage. We'll have to hope Sean c...
by Diminished
Thu Sep 10, 2020 1:30 am
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15532

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

There were a lot of differences between the two dumps, but predictably the majority of those mistakes turned out to be my own. Having corrected those, I see four differences between my 8271 dump and guesser's. I've checked the differing rows multiple times, but since I've marked up a grand total of ...
by Diminished
Thu Sep 10, 2020 12:30 am
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15532

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

Blimey! =D> Unfortunately I still have to go through the ROM by hand and manually mark each bit with a coloured square. This isn't some image processing magic. :( But at least this way, the final step of converting to hex is automated. However, your timing is good, because I have just a few minutes ...
by Diminished
Wed Sep 09, 2020 1:31 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15532

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

Program ROM, first attempt. Mistakes are guaranteed. program_rom.png I'll have a shot at reading this algorithmically after lunch, unless someone else fancies doing it. Raw; I'll get bytes out in a sec. 10101000 10101001 10101000 10101000 11011100 01101001 11111101 11111001 10101010 11111110 1010101...
by Diminished
Sun Sep 06, 2020 8:44 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15532

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

They're transistors, yes? Not resistors? edit: One more I missed, Rich, in the right-hand PLA: 1111 1111 FF xxxx xxxx 00-FF <- this one 0xxx xxxx 00-7F This one doesn't involve a transistor, but the column is just connected directly to one of the row feeds. pla_2_miss.jpg I don't know whether this m...
by Diminished
Sun Sep 06, 2020 7:30 pm
Forum: 8-bit acorn hardware
Topic: 8271 disc controller de-cap and craziness -- do not try this at home!
Replies: 445
Views: 15532

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

I'm concerned a bit about those three columns in the right table which don't appear to be connected to anything whatsoever. I might trace those lines later and see if they actually go anywhere. Checked them, and indeed, they don't seem to be! pla2_unconnected.jpg So I think these three can just be ...

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