Search found 1595 matches

by BigEd
Sat Feb 24, 2018 12:08 pm
Forum: acorn atom
Topic: UEF/CSW support Atomulator
Replies: 38
Views: 1304

Re: UEF/CSW support Atomulator

Excellent sleuthing!
by BigEd
Sat Feb 24, 2018 9:20 am
Forum: off-topic
Topic: This guy made a 'C5' twice as good 70 years earlier...
Replies: 5
Views: 323

Re: This guy made a 'C5' twice as good 70 years earlier...

A massively heavy vehicle with limited power isn't going to have much acceleration - that's fine for milk floats, not so much for heavy traffic. Electric motor technology has come on enormously since the days of the milk float and the C5. (As has battery technology, but that's a different axis.)
by BigEd
Wed Feb 21, 2018 9:22 pm
Forum: hardware
Topic: Pi Zero Super Interface
Replies: 12
Views: 355

Re: Pi Zero Super Interface

You can arrange for a (complex) circuit sitting in a ROM socket to accept writes to a channel by mapping reads to some page as writes of that value. (I think one of John Kortink's designs does this.) So for example a read from &BCxx is a write of xx to channel 0, to &BDxx is a write of xx to...
by BigEd
Wed Feb 21, 2018 6:59 pm
Forum: off-topic
Topic: High school student building 70's era chip fab in his garage
Replies: 3
Views: 247

Re: High school student building 70's era chip fab in his garage

I remember back in the day direct write to wafer using electron beam lithography looked like it might take over the world. (See here , from 1983, and here , from 1980.) But it didn't - that time around. It only really works for low volume, which suits IBM super expensive mainframe chips, and also sm...
by BigEd
Wed Feb 21, 2018 6:49 pm
Forum: off-topic
Topic: Why did CISC prevail?
Replies: 21
Views: 642

Re: Why did CISC prevail?

Ah, but did Thumb become Thumb-2? Or did they design something new from scratch and call it Thumb-2? This might, or might not, help: ARM instructions have fixed-width 4-byte encodings which require 4-byte alignment. Thumb instructions have variable-length (2 or 4-byte, now known as "narrow&quo...
by BigEd
Wed Feb 21, 2018 5:37 pm
Forum: off-topic
Topic: Work experience BITD - claims to fame, and infamy
Replies: 15
Views: 816

Re: Work experience BITD - claims to fame, and infamy

We visited a nuclear power station for a sixth form school trip - from Staffordshire down to Oldbury on the river Severn. I have a recollection of seeing or even being on the floor above the reactor, but that might be a false memory. https://goo.gl/maps/Z49ccRRqNv42 It's not work experience though -...
by BigEd
Wed Feb 21, 2018 4:11 pm
Forum: hardware
Topic: Pi Zero Super Interface
Replies: 12
Views: 355

Re: Pi Zero Super Interface

When we first hooked up Pi to Beeb, IIRC, there was no Pi Zero, so a Pi was £20+ and too big to fit under the machine. Now that Pi Zero is both available and affordable, a two-pi system is perhaps worth considering. I think we've mentioned this in conversation at least: the bare-metal Pi could trans...
by BigEd
Wed Feb 21, 2018 11:40 am
Forum: off-topic
Topic: Thermionic Valves
Replies: 26
Views: 785

Re: Thermionic Valves

> nixie tubes If we're talking about not-quite-valves, the dekatron-based WITCH computer might be of interest! It's on display and is running most days at The National Museum of Computing on Bletchley Park. It has some relays too so it makes a nice ticketty-clunking sound as it computes. https://www...
by BigEd
Tue Feb 20, 2018 4:07 pm
Forum: general
Topic: Acorn Computer (System 1 as it’s known now) Review
Replies: 6
Views: 223

Re: Acorn Computer (System 1 as it’s known now) Review

If you can only think of a computer as being something like a vic-20, you're likely to reach some different conclusions compared to someone who doesn't think that way.
by BigEd
Tue Feb 20, 2018 9:39 am
Forum: projects
Topic: Making reasonable progress with a Sudoku solver
Replies: 35
Views: 738

Re: Making reasonable progress with a Sudoku solver

Ah, this makes more sense now!
by BigEd
Mon Feb 19, 2018 4:58 pm
Forum: projects
Topic: Making reasonable progress with a Sudoku solver
Replies: 35
Views: 738

Re: Making reasonable progress with a Sudoku solver

Here's something interesting - the solver gives up on this one : . . . | . . . | . . 9 . . . | . . 1 | . 3 5 . . 3 | . 9 . | . 6 . -------+-------+------- . . 5 | . 3 . | . . 6 . 7 . | . . 2 | . . . 1 . . | 4 . . | . . . -------+-------+------- . . 9 | . 8 . | . 5 . . 2 . | 7 . . | . . . 4 . . | . ....
by BigEd
Mon Feb 19, 2018 4:40 pm
Forum: projects
Topic: Making reasonable progress with a Sudoku solver
Replies: 35
Views: 738

Re: Making reasonable progress with a Sudoku solver

It's an interesting area! My own approach to tackling a sudoku problem sometimes leaves me stuck, even when there is a solution - so "hard" is certainly relative to tactics employed.

Edit: oops, meant to link here.
by BigEd
Mon Feb 19, 2018 3:52 pm
Forum: projects
Topic: Making reasonable progress with a Sudoku solver
Replies: 35
Views: 738

Re: Making reasonable progress with a Sudoku solver

There are a few difficult sudoko challenges here , and this one took 108.65s on jsbeeb: . . . | . . . | . . 8 . . 3 | . . . | 4 . . . 9 . | . 2 . | . 6 . -------+-------+------- . . . | . 7 9 | . . . . . . | . 6 1 | 2 . . . 6 . | 5 . 2 | . 7 . -------+-------+------- . . 8 | . . . | 5 . . . 1 . | . ...
by BigEd
Mon Feb 19, 2018 12:07 pm
Forum: projects
Topic: Making reasonable progress with a Sudoku solver
Replies: 35
Views: 738

Re: Making reasonable progress with a Sudoku solver

many thanks!

("L" to load T.HARDEST or T.17CELLS)
by BigEd
Mon Feb 19, 2018 10:39 am
Forum: projects
Topic: Making reasonable progress with a Sudoku solver
Replies: 35
Views: 738

Re: Making reasonable progress with a Sudoku solver

This looks very nice to me! Could a clever person please cook up a link to jsbeeb which directly loads and boots the SSD?
by BigEd
Sun Feb 18, 2018 9:28 am
Forum: acorn atom
Topic: Case for your Atom from back in the day
Replies: 4
Views: 176

Re: Case for your Atom from back in the day

Ah, that could be it - in the case of a chargeback the customer wins and the retailer loses, and that might be too much to bear.
by BigEd
Sat Feb 17, 2018 9:22 pm
Forum: off-topic
Topic: Romance is dead
Replies: 6
Views: 333

Re: Romance is dead

I wonder what did it? The news of an Issue 1 selling on ebay???

(Previous high score was in July 2016, when PiTubeDirect was featured on Hackaday)
by BigEd
Sat Feb 17, 2018 7:39 pm
Forum: acorn atom
Topic: Case for your Atom from back in the day
Replies: 4
Views: 176

Re: Case for your Atom from back in the day

Maybe there was very little profit in the Beeb so the retailer's credit card charge was too much to bear? Do we know what price Acorn charged the retailer?
by BigEd
Sat Feb 17, 2018 6:16 pm
Forum: general
Topic: Acorn Computer (System 1 as it’s known now) Review
Replies: 6
Views: 223

Re: Acorn Computer (System 1 as it’s known now) Review

Nice - thanks! I wonder if I might have read that back in the day. There's an 80 page version of the UPPER CASE user manual here http://chrisacorns.computinghistory.org.uk/docs/Acorn/Manuals/Acorn_System1UserManual.pdf and the technical manual here http://chrisacorns.computinghistory.org.uk/docs/Aco...
by BigEd
Fri Feb 16, 2018 5:36 pm
Forum: for sale / freebies
Topic: sundry modems collect-only: Stoke on Trent
Replies: 0
Views: 121

sundry modems collect-only: Stoke on Trent

just in case there's interest, Anthony Rogers says:
Does any one in the Stoke on Trent (UK) area want a mixed box of modems? Mixed types and speeds. [Collect only]


(Probably not acorn-specific, so mods, please delete if that's the right thing to do.)
by BigEd
Fri Feb 16, 2018 10:09 am
Forum: hardware
Topic: Music 5000 - sound generation
Replies: 12
Views: 397

Re: Music 5000 - sound generation

I wouldn't expect to see it used as a sound peripheral for a game. There a quote from Nick "Orlando" Pelling about using the Music 500 in Firetrack 2 in the Lost & Found section of the Stairway to Hell site. He basically says the same thing - it just takes up too much of the CPU's tim...
by BigEd
Fri Feb 16, 2018 9:27 am
Forum: hardware
Topic: Music 5000 - sound generation
Replies: 12
Views: 397

Re: Music 5000 - sound generation

Interesting idea - I'm sure it would be technically possible, but I don't know what BeebSID and BeebOPL actually do.
by BigEd
Thu Feb 15, 2018 9:04 pm
Forum: hardware
Topic: Music 5000 - sound generation
Replies: 12
Views: 397

Re: Music 5000 - sound generation

I think the primary description is a wavetable synthesiser, which means each voice can be an arbitrary waveform. That doesn't make it a sampling synth - the samples are far too short to qualify, usually they'd be a single cycle of a waveform. The "ring modulator" capability seems very basi...
by BigEd
Thu Feb 15, 2018 5:51 am
Forum: hardware
Topic: Music 5000 - sound generation
Replies: 12
Views: 397

Re: Music 5000 - sound generation

Hoglet and I investigated the Music 5000 design, finding it ingenious and wonderful, and I wrote some notes over here: http://forum.6502.org/viewtopic.php?f=4&t=4436 - high quality phase-accumulating wavetable synthesiser, 16 note polyphonic. - low part count, all TTL with two RAMs, plus a DAC. ...
by BigEd
Wed Feb 14, 2018 6:39 pm
Forum: programming
Topic: ADFS Format
Replies: 20
Views: 744

Re: ADFS Format

I'm not sure there's any wear involved when writing to a floppy. There will be wear according to how much time the disk rotates under the (loaded) head, but because the disk keeps spinning for a while after each access, that might be regarded as per-track wear rather than per-sector wear, and would ...
by BigEd
Thu Feb 08, 2018 7:44 pm
Forum: other vintage computer hardware, software and games
Topic: Apple II Super Serial Card Rebuild
Replies: 19
Views: 438

Re: Schematic notation...

I would say links you can cut (bow ties) or pad-pairs you can short (droids)
by BigEd
Thu Feb 08, 2018 4:34 pm
Forum: off-topic
Topic: Why did CISC prevail?
Replies: 21
Views: 642

Re: Why did CISC prevail?

(I found myself reading this presentation by Richard Grisenthwaite of ARM, from 2009 I think, on the evolution of ARM offerings and the difficulties of designing a successful architecture.) While SPARC and POWER might still have a little life in them, and even MIPS too , I think we should look to RI...
by BigEd
Sat Feb 03, 2018 6:12 pm
Forum: hardware
Topic: R65C02 in a Beeb
Replies: 51
Views: 1234

Re: R65C02 in a Beeb

It's not totally surprising that the CMOS part is a bit marginal, especially with the unusually fast edge rates, but it's a major surprise to me that it would affect SBC and nothing else!

An excellent adventure.
by BigEd
Sat Feb 03, 2018 8:59 am
Forum: hardware
Topic: R65C02 in a Beeb
Replies: 51
Views: 1234

Re: R65C02 in a Beeb

That is odd. If SBC is tested first, it might be worth reversing that to see if ADC ever fails. If ADC is already tested first and never fails, that's a datapoint.
by BigEd
Fri Feb 02, 2018 10:37 pm
Forum: hardware
Topic: R65C02 in a Beeb
Replies: 51
Views: 1234

Re: R65C02 in a Beeb

Hmm, and that's a different SBC from last time... Is SBC tested before ADC? Is it always an SBC which fails? I wonder if there's some pattern sensitivity such that the E9 opcode is more problematic than the 69 opcode?? I'm supposing - not sure why - that the opcode is affecting the reliability of re...