Search found 1180 matches

by Coeus
Sat Feb 23, 2019 4:59 pm
Forum: off-topic
Topic: Retro upgrades, value for money, eBay & why bother?
Replies: 48
Views: 1091

Re: Retro upgrades, value for money, eBay & why bother?

Very sad that someone has shown himself to be so mean spirited. @RobC - I don't know where you fall back to in that circumstance. Presumably they got banned because of complaints from other eBayers too but for an obvious breech of eBay's own policy you'd have thought they would step in there. Presum...
by Coeus
Sat Feb 23, 2019 4:28 pm
Forum: off-topic
Topic: Retro upgrades, value for money, eBay & why bother?
Replies: 48
Views: 1091

Re: Retro upgrades, value for money, eBay & why bother?

I had to complain about one fraudster who was selling 74LSxxx very cheaply in multiple batches. I bought a load, he marked them as dispatched, then said he was out of stock and cancelled my order. In the meantime he amended the listing to reduce the quantity per item and increase the price, and car...
by Coeus
Sat Feb 23, 2019 2:56 pm
Forum: emulators
Topic: B-em on OSX with M5000 support
Replies: 14
Views: 354

Re: B-em on OSX with M5000 support

Looking into this even more, the &FE doesn't exist in real hardware and if the compiler is very good it should be optimised away . Bit 0 is the disable bit. If it is set the FREQ macro isn't used. If bit 0 is clear then the macro is use and the &FE is implied. gcc 8.2.1 is not clever enough to have...
by Coeus
Fri Feb 22, 2019 11:43 pm
Forum: emulators
Topic: B-em on OSX with M5000 support
Replies: 14
Views: 354

Re: B-em on OSX with M5000 support

I couldn't hear the difference either but, as the consensus seems to be it is a bug, I have pushed the fix to master in github.
by Coeus
Fri Feb 22, 2019 11:40 am
Forum: hardware
Topic: Sideways Ram
Replies: 19
Views: 380

Re: Sideways Ram

Glued into spare ROM space ... Where might I find Information on merging ROMs? I don't think there is an automated way to do this. The first step is to identify a ROM which has the spare space, usually inidcated by the bytes at the end of the ROM still being all FF or 00. Next, if you have the sour...
by Coeus
Mon Feb 18, 2019 11:10 am
Forum: off-topic
Topic: Retro upgrades, value for money, eBay & why bother?
Replies: 48
Views: 1091

Re: Retro upgrades, value for money, eBay & why bother?

cmorley wrote:
Mon Feb 18, 2019 7:08 am
Follow up.

I did as leenew suggested and contacted eBay customer services at the weekend (webform). I got a response from eBay this morning and they have deleted the negative feedback.
That's great news, Chris, and well-deserved.
by Coeus
Mon Feb 18, 2019 11:08 am
Forum: emulators
Topic: B-em on OSX with M5000 support
Replies: 14
Views: 354

Re: B-em on OSX with M5000 support

Thanks for your reply Coeus. I'll see what I can find. It might not make any difference anyway to the latency........I will revisit it sometime. I you remember the latency is due to the buffer size inside b-em which can be adjusted from the config file. What a different OS may do is allow this buff...
by Coeus
Wed Feb 13, 2019 8:31 pm
Forum: general
Topic: Bit of fun Part Two - CPU Swap
Replies: 28
Views: 640

Re: Bit of fun Part Two - CPU Swap

If Acorn had used a Z80, then I would have expected them to have designed the system to “boot” to BASIC in ROM. Just like the 6502 BBC Micro does. Interestingly, Research Machines, which had not bid for the BBC contract, once the BBC micro was taking part of their market in education, developed the...
by Coeus
Tue Feb 12, 2019 10:02 pm
Forum: other vintage computer hardware, software and games
Topic: Early Rare Digital Synth on CP/M Machine in Action...
Replies: 6
Views: 300

Re: Early Rare Digital Synth on CP/M Machine in Action...

I bet that's just crying out for a MIDI card, if there was enough processing capability to handle it. Not on the original machine, but if you read the full thread BrokenARM linked, a friend of his was able to implement one that sits between the keyboard/controller and the processor. The sound sampl...
by Coeus
Tue Feb 12, 2019 7:38 pm
Forum: off-topic
Topic: Sound Export
Replies: 23
Views: 636

Re: Sound Export

I finally ended up using the debugger in B-Em to monitor writes to the sound IC, and sent a middle-C BELL, and it wrote &EE which gives 525Hz which is C above middle C (very approximately, middle C is 256Hz). C above C is SOUND 149 not SOUND 101, making middle C SOUND 53. Which. Makes. No. Sense. H...
by Coeus
Tue Feb 12, 2019 4:35 pm
Forum: off-topic
Topic: Retro upgrades, value for money, eBay & why bother?
Replies: 48
Views: 1091

Re: Retro upgrades, value for money, eBay & why bother?

At the other end you've got hipster-types who don't know much about the original kit and are used to paying Amazon prices for mass produced stuff from China. They have little to no idea what it costs or how long it takes to develop and assemble the products, they just think it seems expensive when ...
by Coeus
Tue Feb 05, 2019 11:45 pm
Forum: general
Topic: Why was Repton so loved by BBC users yet so disliked by the Commies?
Replies: 72
Views: 1979

Re: Why was Repton so loved by BBC users yet so disliked by the Commies?

...A quick example; the standard 6502 has no ability to disconnect the address and data buses from the rest of the system, something that's needed for DMA. In the VIC-20 Commodore had to put four bus buffer chips on the motherboard to do that job. For the C64 they designed a modified 6502, the 6510...
by Coeus
Tue Feb 05, 2019 11:27 pm
Forum: software: other
Topic: BBC *Status Command (and odd characters)
Replies: 24
Views: 477

Re: BBC *Status Command (and odd characters)

I guess the question therefore is whether there would be any merit in a Teletext printer convertor (which would be in addition to the ESC/P and PCL convertors). It would be based on the explanation at http://central.kaserver5.org/Kasoft/Typeset/BBC/Ch28.html If the Retro Printer is behaving like a ...
by Coeus
Tue Feb 05, 2019 10:09 pm
Forum: software: other
Topic: BBC *Status Command (and odd characters)
Replies: 24
Views: 477

Re: BBC *Status Command (and odd characters)

Or like this in Mode 7:
status.png
The other interesting thing I notice about that ROM is does the OSBYTE version of *TV in response to ROM service call 1 this shifting the display up. This does seem to be a ROM that suited the authors taste.
by Coeus
Tue Feb 05, 2019 6:58 pm
Forum: general
Topic: Why was Repton so loved by BBC users yet so disliked by the Commies?
Replies: 72
Views: 1979

Re: Why was Repton so loved by BBC users yet so disliked by the Commies?

A computer is a processor, memory, and input / output devices that can perform useful work. So a Wii is a computer, as it has all those elements. Games consoles are just specialist computers. In the same way that there are many other designs of specialist computers. True, program development is mor...
by Coeus
Tue Feb 05, 2019 6:48 pm
Forum: general
Topic: Why was Repton so loved by BBC users yet so disliked by the Commies?
Replies: 72
Views: 1979

Re: Why was Repton so loved by BBC users yet so disliked by the Commies?

Indeed. But there's also an elephant in the room. British computer manufacturers were almost uniform in being too blooming cheap to invest in the one thing they really needed; custom chip design. If Sinclair had been able to fund custom video and sound chip designs, rather than sticking with 8-bit ...
by Coeus
Tue Feb 05, 2019 3:38 pm
Forum: software: other
Topic: BBC *Status Command (and odd characters)
Replies: 24
Views: 477

Re: BBC *Status Command (and odd characters)

Can someone with a printer connected to the BBC please check how the *STATUS command appears when printed on a dot matrix printer? There is no *STATUS command on a standard BBC B with OS 1.20. There is a *STATUS command on a BBC Master but that gives different output from what you are trying to pri...
by Coeus
Tue Feb 05, 2019 2:04 pm
Forum: general
Topic: Bit of fun - One change only
Replies: 68
Views: 1769

Re: Bit of fun - One change only

So without the contraint about it being cheap, it would have to be shadow RAM. As 16K would not be enough, my plan would be to make the bottom 1K of RAM common to both banks and then switch the whole of the next 31K between the two banks. This would put OSHWM at &0400 on both I/O processor and tube ...
by Coeus
Mon Feb 04, 2019 8:01 pm
Forum: software: other
Topic: Extended vectors - huh?
Replies: 17
Views: 1148

Re: Extended vectors - huh?

One example where it would obviously go seriously wrong is if you trapped BRKV that way. Surely not. The OS selects the current language before dispatching via BRKV. See this code from the OS: DC27 TXA ;save X on stack DC28 PHA ; DC29 TSX ;get status pointer DC2A LDA &0103,X ;get Program Counter lo...
by Coeus
Mon Feb 04, 2019 1:54 pm
Forum: software: other
Topic: Extended vectors - huh?
Replies: 17
Views: 1148

Re: Extended vectors - huh?

I'm not clear: are you saying you believe that's not a problem, or were you ignoring that consideration? It is certainly possible to imagine a case where it could be a problem. For example, someone writes a piece of code that is assembled from BASIC, calls subroutines in the BASIC ROM and thus reli...
by Coeus
Sun Feb 03, 2019 10:31 pm
Forum: emulators
Topic: B-em on OSX with M5000 support
Replies: 14
Views: 354

Re: B-em on OSX with M5000 support

I can't offer to compile B-Em for OSX as I don't have a Mac and don't have any immediate plans to buy one. I do think someone did compile it on OSX recently, though. I believe Allegro 5 supports OSX, most of B-Em is ANSI C with a little bit of POSIX that Windows seems to implement so OSX should supp...
by Coeus
Sun Feb 03, 2019 10:24 pm
Forum: software: other
Topic: Extended vectors - huh?
Replies: 17
Views: 1148

Re: Extended vectors - huh?

This suffices for forwarding a call to a previous extended vector claimant. But what about a previous normal vector claimant? Then you just finish by jumping to the address previously in the non-extended vector. So that means when hooking the vector you need to check where the standard vector in pa...
by Coeus
Mon Jan 07, 2019 4:03 pm
Forum: programming
Topic: CRC Calculation
Replies: 11
Views: 313

Re: CRC Calculation

I read the replies with interest this morning but not have a chance to reply until now. So, first of all, sorry for wasting your time to prove that the Perl was indeed correct due to a wrong assumption on my part. I hope, though, it has been an interesting discussion for others besides me. So to be ...
by Coeus
Mon Jan 07, 2019 12:39 am
Forum: programming
Topic: CRC Calculation
Replies: 11
Views: 313

CRC Calculation

I am slightly puzzled by a piece of code to calculate CRCs. In sweh's TubeHost there is this routine, Perl: sub CalcCRC($) { my $crc=0; foreach my $c (split(//,$_[0])) { $crc ^= (256*ord($c)); foreach my $x (0..7) { $crc *= 2; if ($crc > 65535) { $crc-=65535; $crc ^= 0x1020; } } } return($crc); } Th...
by Coeus
Fri Jan 04, 2019 2:52 pm
Forum: off-topic
Topic: What New Language Should I Learn?
Replies: 21
Views: 397

Re: What New Language Should I Learn?

On the "what projects" side of things, nothing major at least not initially. Most of what I "program" now is to automate or batch process something or other. I usually end up having to search online and turn up examples in bash, perl, python and others, and if I really get stuck I ask on here! Usua...
by Coeus
Thu Jan 03, 2019 1:53 pm
Forum: hardware
Topic: Minimal Tube 6502decode bus snoop with FTDI USB
Replies: 68
Views: 3499

Re: Minimal Tube 6502decode bus snoop with FTDI USB

So another question about the comms mode: is there any kind of flow control, for example the RTS/CTS scheme used by the normal serial port?
by Coeus
Wed Jan 02, 2019 11:59 am
Forum: off-topic
Topic: Which 17" laptop should I buy
Replies: 4
Views: 258

Re: Which 17" laptop should I buy

Don't take this as a recommendation, because I it is not longer a current model and I haven't tried gaming on it, but at work I have been allocated a Lenovo Thinkpad W540 as a "developer laptop", i.e. something quicker than the super-light but rather slow things most people get, but it seems to me L...
by Coeus
Wed Jan 02, 2019 1:40 am
Forum: hardware
Topic: Minimal Tube 6502decode bus snoop with FTDI USB
Replies: 68
Views: 3499

Re: Minimal Tube 6502decode bus snoop with FTDI USB

And two answer my own question, the issue was down to me having naively assumed that OSRDCH waits for a character to become available and then returns it in A. After all, that's the only way I have seen it used, by consulting the documentation it returns with carry clear if it was able to get a char...
by Coeus
Tue Jan 01, 2019 11:58 pm
Forum: hardware
Topic: Minimal Tube 6502decode bus snoop with FTDI USB
Replies: 68
Views: 3499

Re: Minimal Tube 6502decode bus snoop with FTDI USB

I am now getting some weirdness using the serial comms part of this bus snoop adapter and not, I think, the reversed test from before. I thought I'd write a very small program to intercept OSWRCH and OSRDCH to direct ouput via this link, and accept input from it. Just keeping things really simple to...
by Coeus
Mon Dec 31, 2018 10:24 pm
Forum: hardware
Topic: Minimal Tube 6502decode bus snoop with FTDI USB
Replies: 68
Views: 3499

Re: Minimal Tube 6502decode bus snoop with FTDI USB

Brilliant, thanks Dave.