Search found 319 matches

by crj
Thu Dec 14, 2017 4:20 am
Forum: hardware
Topic: Acorn's Second Processors and the Tube - what, and why
Replies: 9
Views: 350

Re: Acorn's Second Processors and the Tube - what, and why

The Tube hardware in the Beeb is not that special. [...]The second thing that makes the difference, is Acorns concept and actual released products. Which of course contain the Tube ULA. That wasn't emphasised much at the time, but is a big part of the cleverness of the Tube architecture. In the BBC...
by crj
Thu Dec 14, 2017 2:22 am
Forum: hardware
Topic: Acorn's Second Processors and the Tube - what, and why
Replies: 9
Views: 350

Re: Acorn's Second Processors and the Tube - what, and why

The IO was intended to be essentially text passed back & forth. This means it doesn’t lend itself to real time applications like games particularly well. I'm not sure either part of that is really true. By having four FIFOs, the Tube supports a fairly rich set of binary protocols, and filing sy...
by crj
Thu Dec 14, 2017 1:08 am
Forum: software: other
Topic: Wishful thinking - B+ OS, C/C++ DFS/ADFS
Replies: 6
Views: 156

Re: Wishful thinking - B+ OS, C/C++ DFS/ADFS

Aha, thanks!
by crj
Thu Dec 14, 2017 12:20 am
Forum: software: other
Topic: Wishful thinking - B+ OS, C/C++ DFS/ADFS
Replies: 6
Views: 156

Wishful thinking - B+ OS, C/C++ DFS/ADFS

I'm struggling to find a couple of things... The first is a copy of the BBC B+ MOS. I'm sure it must be out there somewhere on the Internet, but it's not an easy thing to Google for. One with disassembly would be superb, of course, but beggars can't be choosers. The second I'm less sure will exist: ...
by crj
Wed Dec 13, 2017 7:44 pm
Forum: hardware
Topic: Master Keyboard Issue - need expert opinions
Replies: 4
Views: 113

Re: Master Keyboard Issue - need expert opinions

First thing to do is test F6. If F6 is working, you know the break is on the track between F6 and M. If it's not, I guess the next step is to unplug the keyboard and test continuity between F6 and the connector. Then temporarily plug the keyboard back in and boot the machine (so you can get to a pro...
by crj
Tue Dec 12, 2017 2:06 am
Forum: software: new games
Topic: New Release: Retro Software's WHITE LIGHT by Sarah Walker
Replies: 47
Views: 1456

Re: New Release: Retro Software's WHITE LIGHT by Sarah Walker

Having sworn at Disc Doctor for years, I then switched to swearing by ADT. A far more solid and accomplished offering!
by crj
Sun Dec 10, 2017 5:12 pm
Forum: hardware
Topic: Only the Break key works on Keyboard
Replies: 9
Views: 210

Re: Only the Break key works on Keyboard

I've never personally had to diagnose a keyboard fault on a Beeb, but as I understand it: ⋅ Mainboard works (with a different keyboard) ⋅ LEDs work (so +5V present) ⋅ Break works (so 0V present) ⋅ Not even a single other key on the keyboard works (not an isola...
by crj
Sun Dec 10, 2017 1:59 am
Forum: hardware
Topic: Problem Beeb MotherBoard
Replies: 68
Views: 1203

Re: Problem Beeb MotherBoard

Elaborating on that, in MODE 7 a RAM fault will manifest as incorrect characters (or teletext graphic/colour effects) being displayed. A fault further down the video chain, conversely, could manifest as corrupted characters, some kind of mess you couldn't possibly produce no matter what you put in m...
by crj
Sat Dec 09, 2017 3:19 pm
Forum: other vintage computer hardware, software and games
Topic: Computer ad and review compilations
Replies: 5
Views: 183

Re: Computer ad and review compilations

Wow! That's an impressive slab of metal under that Shugart 14" hard drive!
by crj
Fri Dec 08, 2017 3:14 pm
Forum: general
Topic: Today I received.....
Replies: 4317
Views: 251511

Re: Today I received.....

Coo! Those are modern replicas, aren't they? (No / on f0, slightly different typeface, owl keys.)

What are you up to? (-8
by crj
Fri Dec 08, 2017 3:08 pm
Forum: hardware
Topic: BBC Micro: writes to ROM?
Replies: 10
Views: 358

Re: BBC Micro: writes to ROM?

Ah, the ATPL Sidewise.

That was a solid bit of kit, what I selected for my own BBC B at home. Which sadly got burgled so I no longer have it. The silver lining was BBC Master being launched between the burglary and the insurance payout!
by crj
Fri Dec 08, 2017 4:37 am
Forum: general
Topic: Computer Shops From Back In The Day
Replies: 65
Views: 5651

Re: Computer Shops From Back In The Day

So what's that in the kid's pocket? It can't have been a mobile phone and I certainly hope it wasn't a packet of cigarettes!
by crj
Thu Dec 07, 2017 7:02 pm
Forum: emulators
Topic: Music 5000 in B-Em
Replies: 181
Views: 6860

Re: Music 5000 in B-Em

fordp wrote:How does the latency compare to a pro midi synth?

Synths will vary, and I can't speak specifically to the issue of MIDI, but back when I was helping to develop realtime pro audio kit, our target was around 5ms from the user touching the control surface to audible result.
by crj
Thu Dec 07, 2017 6:53 pm
Forum: stardot.org.uk
Topic: https certificates?
Replies: 41
Views: 1611

Re: https certificates?

That's not the only difference.

The more important differences aren't technical: they're relatively reputable by the standards of the day, and large enough to be accountable to the court of public opinion if they ever screw me over.
by crj
Thu Dec 07, 2017 12:54 am
Forum: hardware
Topic: BBC Micro: writes to ROM?
Replies: 10
Views: 358

Re: BBC Micro: writes to ROM?

1024MAK wrote:But keep in mind that most chips can only output up to around 25mA into a short circuit, or sink a similar amount.

Hmm. I may have misconstrued.

I thought those limits meant the chip would break if you ever tried to source/sink more, not that it would current-limit!
by crj
Thu Dec 07, 2017 12:49 am
Forum: hardware
Topic: Unusual mask ROM in Master 128
Replies: 8
Views: 236

Re: Unusual mask ROM in Master 128

But... by my understanding ~CS is tied permanently low on the MOS ROM in the BBC Master, i.e. it's always enabled.

If early chips got that wrong, why the need for the logic chip? Would it not have sufficed for the carrier to tie CS to +5V?
by crj
Wed Dec 06, 2017 6:15 pm
Forum: hardware
Topic: BBC Micro: writes to ROM?
Replies: 10
Views: 358

Re: BBC Micro: writes to ROM?

So... what limits the current that flows if a ROM drives 1 and the CPU drives 0 or vice-versa?

Is that current sustainable? And is the limit by luck or by design?
by crj
Wed Dec 06, 2017 5:23 pm
Forum: hardware
Topic: BBC Micro: writes to ROM?
Replies: 10
Views: 358

BBC Micro: writes to ROM?

In an interesting discussion away from the forums, somebody pointed out an interesting thing to me: the processor's R/~W line features nowhere in the driving of ~CE or ~OE to the ROMs. I've checked this on the schematic and it appears to be true. Doesn't that mean that there's a bus clash every time...
by crj
Wed Dec 06, 2017 5:12 pm
Forum: stardot.org.uk
Topic: https certificates?
Replies: 41
Views: 1611

Re: https certificates?

OV feels like the most appropriate kind of certificate: it actually gives some assurance of identity beyond "this person was in control of the domain when they applied", but isn't an expensive status symbol like EV. Once upon a time, it was the only kind of certificate one could get. DV is...
by crj
Wed Dec 06, 2017 4:53 pm
Forum: hardware
Topic: RISC OS 3.20 ROM's?
Replies: 117
Views: 2762

Re: RISC OS 3.20 ROM's?

I guess the question is academic at this point, but why do so many modules break if you put them in ROM? They're not coded to work from ROM, either they store values internally or they're coded in C and not compiled specifically for ROM. I noted - and sadly understand - the issue with SharedCLibrar...
by crj
Tue Dec 05, 2017 8:00 pm
Forum: hardware
Topic: Clwyd Technics Colour Palette enhancer
Replies: 7
Views: 288

Re: Clwyd Technics Colour Palette enhancer

Evil thought: with modern hardware, could you make a unit like that which was completely non-invasive and didn't need to attach to the User Port?

Use a split-mode hack to transmit the palette information during flyback? (-8<
by crj
Tue Dec 05, 2017 7:57 pm
Forum: hardware
Topic: Pi-based Co-Pro on the cheap - 100MHz 6502 for £10? (now 274MHz)
Replies: 1003
Views: 75303

Re: Pi-based Co-Pro on the cheap - 100MHz 6502 for £10? (now 274MHz)

Hmm. I realise I always assumed that disc/Econet filesystems accessed the Tube directly from their NMI handlers when loading or saving to/from a second processor, in which case in practice the delay NOPs would likely not be needed because the transfer was slow enough anyway. If this is an issue, I g...
by crj
Tue Dec 05, 2017 6:46 pm
Forum: hardware
Topic: RISC OS 3.20 ROM's?
Replies: 117
Views: 2762

Re: RISC OS 3.20 ROM's?

I guess the question is academic at this point, but why do so many modules break if you put them in ROM? SharedCLibrary is obviously unfortunate, but I get the strong impression that's not the only problem. Yet back when I was writing relocatable modules I don't recall any difficulty keeping code ap...
by crj
Tue Dec 05, 2017 6:14 pm
Forum: other vintage computer hardware, software and games
Topic: ZX Spectrum next... Anybody backing ?
Replies: 82
Views: 3296

Re: ZX Spectrum next... Anybody backing ?

Note that external bus width and CPU microarchitecture don't need to correspond. The Motorola 68008 had 32-bit registers and a 16-bit internal data bus, but an 8-bit external data bus. Conversely, PC DIMMs are 64-bit despite being initially appearing in machines with 32-bit x86es.
by crj
Tue Dec 05, 2017 5:41 pm
Forum: hardware
Topic: Clwyd Technics Colour Palette enhancer
Replies: 7
Views: 288

Re: Clwyd Technics Colour Palette enhancer

Interesting! The notion that such effects could be achieved by outboard postprocessing is obvious now I see it, but hadn't occurred to me before. A significant limitation, of course, is that it can only do eight colours that way. You can't get an extra eight in the way you can if you usurp the video...
by crj
Tue Dec 05, 2017 2:12 am
Forum: hardware
Topic: Switchable/dynamic/expanded RISC OS
Replies: 25
Views: 606

Re: Switchable/dynamic/expanded RISC OS

Has anyone, ever, put a 4Mbyte ROM set in an Archimedes, or heard of anyone ever doing it? As I say, the schematics suggest to me very strongly that the extra address line is latched, but not physically present on the ROM sockets. That means it ought to be possible to acquire it with a single flying...
by crj
Mon Dec 04, 2017 6:08 pm
Forum: hardware
Topic: Switchable/dynamic/expanded RISC OS
Replies: 25
Views: 606

Re: Switchable/dynamic/expanded RISC OS

Doubling up the size to 8MB so two ROM's can be hosted with a jumper to switch between them would also be a prudent move. The moment you move away from trying to find chips that directly fit the socket, and instead have DIL headers going to a PCB with modern chips, capacities become irrelevantly hu...
by crj
Mon Dec 04, 2017 5:54 pm
Forum: hardware
Topic: Switchable/dynamic/expanded RISC OS
Replies: 25
Views: 606

Re: Switchable/dynamic/expanded RISC OS

The biggest limitation being the SMD chip may be difficult to fit on the PCB without fouling some of the DIL pins. One interesting product in that respect is the Preci-dip 350-PP-1NN-01-899101 range. I've not yet acquired samples, because I know they can't be hand-soldered, but they appear to be DI...
by crj
Sun Dec 03, 2017 9:51 pm
Forum: wanted
Topic: Would like to borrow: Hydra controller card
Replies: 15
Views: 571

Re: Would like to borrow: Hydra controller card

If (if) people are prepared to pay that much, it's almost worth reimplementing the Hydra from scratch!

Or just tracking down some ex-Simtec people, asking nicely for an IP licence and sending the Gerbers off to some random Chinese PCB assembler.
by crj
Sun Dec 03, 2017 9:45 pm
Forum: introduce yourself
Topic: Hello
Replies: 10
Views: 264

Re: Hello

Ah, Great Britain Limited! I clearly had the hacker mentality from quite an early age. It turned out you could get some interesting economic results with policies like a VAT rate of -200%. The bounds checking wasn't especially good, and often you could plod on for quite a while in a nether world of ...

Go to advanced search