Search found 2488 matches

by BigEd
Mon Jun 17, 2019 7:22 am
Forum: general
Topic: Anti-Ferranti? — BBC Micro news from 1982
Replies: 2
Views: 127

Re: Anti-Ferranti? — BBC Micro news from 1982

Another very interesting scan Lurkio - thanks! I find it interesting that they haven't quite finished the Tube chip but are already talking about offering the 16032 second processor. Here's the text: Delivery problems with BBC micro Delay of 10 weeks for the B micro Herman Hauser says that the probl...
by BigEd
Sun Jun 16, 2019 8:15 pm
Forum: general
Topic: “Send no money now!” — Electron news from 1982
Replies: 8
Views: 214

Re: “Send no money now!” — Electron news from 1982

It would be rather unusual to send money to a company to buy something which wasn't for sale, I'd think - I wonder if the attention-grabbing phrase is a dig at Sinclair, who would habitually advertise a product and take money for it and then not send the product for a very long time - more than once...
by BigEd
Sun Jun 16, 2019 5:06 pm
Forum: general
Topic: “Send no money now!” — Electron news from 1982
Replies: 8
Views: 214

Re: “Send no money now!” — Electron news from 1982

It does seem a surprisingly aggressive timescale, but the same timeline is described in The Register's writeup of the Elk's 30th. (It's because it's surprising, and because it's easy to remember it only as "they missed Christmas", that I commented...) Agreed, though, Lurkio has posted something very...
by BigEd
Sun Jun 16, 2019 6:44 am
Forum: general
Topic: “Send no money now!” — Electron news from 1982
Replies: 8
Views: 214

Re: “Send no money now!” — Electron news from 1982

It's quite remarkable that they hoped to hit the market for Christmas 1982, and wound up missing the market for Christmas 1983.
by BigEd
Sat Jun 15, 2019 7:53 pm
Forum: acorn atom and system
Topic: FPGA Adaptor as Floating Point Coprocessor
Replies: 7
Views: 308

Re: FPGA Adaptor as Floating Point Coprocessor

If the FPGA sits in the 6502 socket it can snoop on the code and on the memory accesses... it will see the two(?) floating point accumulators in zero page as they are updated.
by BigEd
Fri Jun 14, 2019 8:57 am
Forum: programming
Topic: BBC BASIC mysteries and speculation
Replies: 22
Views: 294

Re: BBC BASIC mysteries and speculation

Very true... always tempting to speculate about optimisation, but as we know, best to measure first.
by BigEd
Fri Jun 14, 2019 4:27 am
Forum: programming
Topic: BBC BASIC mysteries and speculation
Replies: 22
Views: 294

Re: BBC BASIC mysteries and speculation

This bump-variable-to-list-head is a very interesting (but simple idea) - how much 6502 code would it be, I wonder, and is there any way to shoehorn it into a Basic 4 revision? (If we still had hyperbolic tangent, we could drop that and save some space... but we don't. So that was a bit of a hyperbo...
by BigEd
Sun Jun 09, 2019 6:46 pm
Forum: general
Topic: Uses for Beebs at British Rail
Replies: 24
Views: 3820

Re: Uses for Beebs at British Rail

I'm told https://www.railforums.co.uk/ might be able to help.
by BigEd
Sun Jun 02, 2019 7:27 pm
Forum: software: other
Topic: Accuracy loss in Basic 4 compared to earlier Basics?
Replies: 22
Views: 501

Re: Accuracy loss in Basic 4 compared to earlier Basics?

Thanks for the traces! They should be very illuminating, once analysed...
by BigEd
Sat Jun 01, 2019 12:15 pm
Forum: software: other
Topic: Accuracy loss in Basic 4 compared to earlier Basics?
Replies: 22
Views: 501

Re: Accuracy loss in Basic 4 compared to earlier Basics?

It's certainly just the final division that differs - and only by one part in four billion - but it's some missed opportunity for rounding, I think. Indeed we should be able to tell by reading the code (very carefully)
by BigEd
Fri May 31, 2019 8:37 pm
Forum: software: other
Topic: Accuracy loss in Basic 4 compared to earlier Basics?
Replies: 22
Views: 501

Re: Accuracy loss in Basic 4 compared to earlier Basics

I'll have to admit to being a bit baffled. Another check with 'bc' and I realise I don't understand what it's doing with fractional values. I'm tempted to say it's wrong! F0F0.F0F1 * F0F0.F0F1 E2C4A67E.FB4EAC6 F0F0F0F1 * F0F0F0F1 E2C4A68886A4C2E1 Not that this changes the observations of what Basic ...
by BigEd
Fri May 31, 2019 11:32 am
Forum: software: other
Topic: Accuracy loss in Basic 4 compared to earlier Basics?
Replies: 22
Views: 501

Re: Accuracy loss in Basic 4 compared to earlier Basics

Hmm, on further investigation... while Basic 2 comes closest to getting the answer closest to 1/17, if we look at what 32-bit arithmetic would produce in the best case, it's a different answer - and Basic 4 is slightly closer! $ bc bc 1.06 Copyright 1991-1994, 1997, 1998, 2000 Free Software Foundati...
by BigEd
Fri May 31, 2019 11:13 am
Forum: software: other
Topic: Accuracy loss in Basic 4 compared to earlier Basics?
Replies: 22
Views: 501

Re: Accuracy loss in Basic 4 compared to earlier Basics

It is the division which is 'wrong' - and it's wrong in the sense that Basic 2's value is closer, and is as close as it can be to the 'expected' value of 1/17.
by BigEd
Fri May 31, 2019 10:27 am
Forum: software: other
Topic: Accuracy loss in Basic 4 compared to earlier Basics?
Replies: 22
Views: 501

Re: Accuracy loss in Basic 4 compared to earlier Basics

For a single computation, we should hope for accuracy within one part in four billion. For chained calculations, errors might accumulate. But I would have hoped that Basic 4 would never be less accurate than Basic 2. Edit: this was meant to be a more thorough test but it didn't show the same "bug" 1...
by BigEd
Fri May 31, 2019 8:30 am
Forum: software: other
Topic: Accuracy loss in Basic 4 compared to earlier Basics?
Replies: 22
Views: 501

Re: Accuracy loss in Basic 4 compared to earlier Basics

I think it's usually one unit in the last place - that is, the least significant bit of the mantissa is wrong.
by BigEd
Fri May 31, 2019 8:03 am
Forum: software: other
Topic: Accuracy loss in Basic 4 compared to earlier Basics?
Replies: 22
Views: 501

Re: Accuracy loss in Basic 4 compared to earlier Basics

With a different test, I'm finding a lot more cases where Basic 2 has the (very slightly) greater error than Basic 4. If that test is representative, Basic 4 is generally - but not always - more accurate for floating point division and multiplication. But it's feeling like a much more extensive test...
by BigEd
Thu May 30, 2019 2:25 pm
Forum: hardware
Topic: BEEB Graphics Screen
Replies: 14
Views: 436

Re: BEEB Graphics Screen

So it would have been possible to rearrange the RAM so that the CPU saw the video RAM as being 8 bit wide, but the CRTC addressed the RAM as a block that is 16 bit wide. Some form of bank switching would be needed, as otherwise there is not enough space in the CPU memory map for the required RAM an...
by BigEd
Wed May 29, 2019 11:30 pm
Forum: software: other
Topic: Accuracy loss in Basic 4 compared to earlier Basics?
Replies: 22
Views: 501

Accuracy loss in Basic 4 compared to earlier Basics?

I was surprised to find the floating point division in (6502) BBC Basic 4 is just a tad less accurate than in previous versions. (Edit: maybe I have the wrong idea of what accuracy is: see below . Added a question mark to the thread title.) It turns out this simple test returns zero for Basic 2 but ...
by BigEd
Wed May 29, 2019 7:29 pm
Forum: acorn atom and system
Topic: Atoms ahoy on HACKADAY!
Replies: 46
Views: 1340

Re: Atoms ahoy on HACKADAY!

(was there something to do with padding, with the exact size of the file??)
by BigEd
Fri May 24, 2019 7:24 am
Forum: upcoming and recent events & exhibitions
Topic: ABUG Cambridge 28th - 30th June 2019 BOOKING THREAD - NOW FULL
Replies: 120
Views: 4291

Re: ABUG Cambridge 28th - 30th June 2019 BOOKING THREAD - NOW FULLY BOOKED

BTW there's a great resource for UK train travel here:
https://traintimes.org.uk/SSD/cambridge ... 2019-06-28
and bear in mind that ticket prices can vary according to time of travel, and advance tickets can be much cheaper than tickets bought on the day of travel.
by BigEd
Thu May 16, 2019 5:19 pm
Forum: emulators
Topic: 50 fps on b-em?
Replies: 18
Views: 535

Re: 50 fps on b-em?

You'll find the majority of emulators only use a single core. If you're emulating a single CPU machine then what do you offload to another core? ... There's a good discussion at https://forums.bannister.org/ubbthreads.php?ubb=showflat&Number=106795. Thanks, good link! The case which is likely to wo...
by BigEd
Thu May 16, 2019 4:40 pm
Forum: hardware
Topic: Beeb 1MHz Bus FPGA Adaptor
Replies: 99
Views: 3080

Re: Beeb 1MHz Bus FPGA Adaptor

Ah, of course I missed that the board does its own (calorifically intense) regulation.

Yes, 240MHz ought to be enough for anyone.
by BigEd
Thu May 16, 2019 4:18 pm
Forum: hardware
Topic: Beeb 1MHz Bus FPGA Adaptor
Replies: 99
Views: 3080

Re: Beeb 1MHz Bus FPGA Adaptor

From 5V to 1.2V is quite a step - is it worth considering a buck converter, which doesn't just turn excess voltage into heat? I don't know why two FPGAs wouldn't get about equally hot when doing the same tasks. It's a pity to lose so much performance, although it's all relative - still a very fast M...
by BigEd
Thu May 16, 2019 11:58 am
Forum: hardware
Topic: Proposed: "The Ultimate Electron Upgrade"
Replies: 367
Views: 23062

Re: Proposed: "The Ultimate Electron Upgrade"

10 PCBs are cheap - 10 sets of parts not so much. Perhaps someone can bring a toaster oven to the ABUG...
by BigEd
Wed May 15, 2019 3:43 pm
Forum: general
Topic: Remarkable videos recently posted on Youtube
Replies: 230
Views: 25533

Re: Remarkable videos recently posted on Youtube

Very nice - thanks!
by BigEd
Wed May 08, 2019 8:28 am
Forum: general
Topic: Acorn Electron press launch event: a shambles?
Replies: 6
Views: 398

Re: Acorn Electron press launch event: a shambles?

Thanks for sharing, lurkio. Sounds cringeworthy. But: green Electron rock! I wonder if anyone anywhere still has that - what's the shelf life of confectionery?
by BigEd
Mon May 06, 2019 8:33 am
Forum: general
Topic: DRAGON USER gripes about the Computer Literacy Programme.....
Replies: 52
Views: 1218

Re: DRAGON USER gripes about the Computer Literacy Programme.....

The ever-informative nosher.net tells us : Dragon had come from nowhere to briefly become one the UK's top-selling micros by the end of 1982, having shifted 50,000 units and ...for a while, the Dragon was considered one of the UK's most popular micros, having sold 80,000 in the first 12 months of it...
by BigEd
Sun May 05, 2019 10:50 am
Forum: hardware
Topic: Help Needed with 6502 Second Processor
Replies: 18
Views: 575

Re: Help Needed with 6502 Second Processor

It's common to have a bad connection, if the Tube connector on the Beeb has never been used. So the advice is to plug and unplug the cable several dozen times, and maybe even clean the pins with the hard kind of pencil eraser. Or more drastically, with a screwdriver: https://stardot.org.uk/forums/vi...