Search found 609 matches

by Coeus
Sun Feb 18, 2018 11:10 pm
Forum: hardware
Topic: B+64K - 12k sideways ram working
Replies: 9
Views: 210

Re: B+64K - 12k sideways ram working

...Not really better than a standard BBC... It does have shadow screen RAM. That was an upgrade available to a standard BBC B back in the day - see http://stardot.org.uk/forums/viewtopic.php?f=3&t=14505 - but is the only such upgrade I can think of that doesn't have a modern re-make so that has...
by Coeus
Sun Feb 18, 2018 9:25 pm
Forum: hardware
Topic: B+64K - 12k sideways ram working
Replies: 9
Views: 210

Re: B+64K - 12k sideways ram working

Who do you think your potential buyers are? I am thinking, for example, that I know what a B+64K is so I know it doesn't come with the normal kind of sideways RAM so that would not be a surprise. I also read that the B+ was generally less common than either the model B or the master which may help i...
by Coeus
Sun Feb 18, 2018 9:15 pm
Forum: off-topic
Topic: Thermionic Valves
Replies: 11
Views: 330

Re: Thermionic Valves

...I do worry about the supply of these things. I believe there are something like four companies worldwide still making them. Oddly, the company that made the devices I bought was IIRC established sometime in the mid 90s, which seems a very strange time to set up a firm making thermionics, but the...
by Coeus
Sun Feb 18, 2018 8:53 pm
Forum: off-topic
Topic: LOLPRICE
Replies: 2711
Views: 202225

Re: LOLPRICE

I am selling it as not working, I do not have time to test it...as I have new projects now and I am having a clear out (again!!) No time to test a £600 computer? More likely it just doesn't work? I'd be surprised if an "untested" item ever turned out to work. If you were the seller why wo...
by Coeus
Sat Feb 17, 2018 1:37 pm
Forum: hardware
Topic: Music 5000 - sound generation
Replies: 12
Views: 364

Re: Music 5000 - sound generation

I guess I could rig up some kind of benchmarking and find out, but does anybody happen to know offhand what percentage of CPU time is burned by servicing interrupts for the Music 5000? (It actually used a User VIA timer, didn't it? I don't believe the Music 5000 itself can actually generate interru...
by Coeus
Fri Feb 16, 2018 7:07 pm
Forum: emulators
Topic: B-Em
Replies: 277
Views: 13417

Re: B-Em

- How is the transition to GLFW going? - Why GLFW and not something like SFML that includes both graphics and audio and controllers? Where did you see this transition mentioned? There was some discussion around the fact the Allegro 4 library which B-Em uses being old and in consequence not building...
by Coeus
Wed Feb 14, 2018 4:01 pm
Forum: programming
Topic: ADFS Format
Replies: 20
Views: 706

Re: ADFS Format

...Load the entire track into RAM, modify it and write it back if you wanted to store a new file in a part-used track. This read-modify-write arrangement is exactly what DFS has to do if you write into the middle of a file, except it does it for sectors rather than tracks. If you write this in basi...
by Coeus
Wed Feb 14, 2018 11:38 am
Forum: programming
Topic: ADFS Format
Replies: 20
Views: 706

Re: ADFS Format

...On a 5.25" floppy the head is moving around the track. To get the catalogue you move the head to track 0, but how do you know when it starts? I know there are index pulses from the hole, so I assume that is involved. Limiting the discussion to soft sectored discs, which the common ones, the...
by Coeus
Mon Feb 12, 2018 11:18 pm
Forum: off-topic
Topic: Dodgy PSUs from China
Replies: 4
Views: 336

Re: Dodgy PSUs from China

After the thread on deathdapters and rumours of cheap PSUs from China catching fire you're brave. On the other hand I thoroughly approve of giving equipment a new lease of life rather than just scrapping it.
by Coeus
Mon Feb 12, 2018 11:13 pm
Forum: hardware
Topic: Open Source Logic Analyzer Experiments
Replies: 132
Views: 5879

Re: Open Source Logic Analyzer Experiments

So somehow the write at the end of the first INC 01 is either ignored, or it is affecting the wrong address. I have a suspicion this read-bank of 01 to increment it to the next value maybe the first read from RAM in the initialisation sequence so maybe writes are being ignored to all addresses, not...
by Coeus
Mon Feb 12, 2018 10:51 pm
Forum: software: games - high scores
Topic: keyboards on PC to play games: Ignored keys with other keys pressed
Replies: 13
Views: 329

Re: keyboards on PC to play games: Ignored keys with other keys pressed

I assume the circuitry required to support many keys pressed in parallel (without producing 'ghost' keypresses) is much more complicated. Not complicated but it does cost a few pence more - it needs extra diodes. If you look at the circuit diagram of the BBC micro keyboard at the bottom of each col...
by Coeus
Sun Feb 11, 2018 5:45 pm
Forum: hardware
Topic: Screen shadow memory
Replies: 18
Views: 525

Re: Screen shadow memory

... but neither the Aries or the Solidisk are fully Master compatible as neither have the ability to display from either bank which the Master can. Meanwhile, I have something in the pipeline which might :) That sounds very interesting. How much RAM does it have and does it map any leftover RAM to ...
by Coeus
Sat Feb 10, 2018 10:12 pm
Forum: programming
Topic: Sideways ROMs, Ctrl-Break and running from SWRAM
Replies: 4
Views: 196

Sideways ROMs, Ctrl-Break and running from SWRAM

I have been experimenting with the patch Master version of ADFS on a B with 65C02 - I have edited the source to make the workspace start a compile time option. It still doesn't work properly but one early puzzle I faced was some code in the SD card patch to only initialise the workspace if the last ...
by Coeus
Sat Feb 10, 2018 10:07 pm
Forum: software: other
Topic: Acorn BBC Micro B Master MMC solid state disk drive
Replies: 3
Views: 183

Re: Acorn BBC Micro B Master MMC solid state disk drive

There are several MMC filing systems so it may help if you knew which one you have which would usually be printed between "Acorn MOS" and "BASIC" on the initial startup screen.
by Coeus
Sat Feb 10, 2018 4:22 pm
Forum: hardware
Topic: Aries B20 Shadow RAM board - user guide and ROM wa
Replies: 8
Views: 1063

Re: Aries B20 Shadow RAM board - user guide and ROM wa

No, the Watford one was crap. The development cycle was: plug it in, does it power up? Yes. market it. I thought the ROM boardc was regarded as working quite well. I have sometimes wondered whether Watford actually had a design/development department of whether independent designers/developers sold...
by Coeus
Sat Feb 10, 2018 3:24 pm
Forum: hardware
Topic: Screen shadow memory
Replies: 18
Views: 525

Re: Screen shadow memory

However, the BBC Master taught us that there's another way: if you watch the address bus and the CPU's "sync" line, you can know the address code is being executed from. The Master's memory controller uses that to make some code use the currently selected screen bank, and other code use t...
by Coeus
Sat Feb 10, 2018 3:02 pm
Forum: hardware
Topic: Screen shadow memory
Replies: 18
Views: 525

Re: Screen shadow memory

The Solidisk 2M128 tries to emulate shadow RAM. It does this by leaving the video memory untouched and pages an alternate bank over. So every time you write a character to the screen (eg a VDU call) it has to set the "write" bank to the original memory, call the original function, then sw...
by Coeus
Sat Feb 10, 2018 12:53 pm
Forum: hardware
Topic: Screen shadow memory
Replies: 18
Views: 525

Screen shadow memory

Looking through the list of modern hardware/remakes one thing that seems to be missing is an add-on to provide shadow memory for the screen for a model B in a similar way to the B+/Master. Does anyone know of such a project?
by Coeus
Fri Feb 09, 2018 6:19 pm
Forum: for sale / freebies
Topic: BeebSCSI mini
Replies: 138
Views: 8807

Re: BeebSCSI mini

There were 14 left after I placed my order. Now down to 10.
by Coeus
Fri Feb 09, 2018 2:22 pm
Forum: hardware
Topic: Open Source Logic Analyzer Experiments
Replies: 132
Views: 5879

Re: Open Source Logic Analyzer Experiments

Not sure why some of them repeat. On an unexpanded model B the ROMS select line is not fully decoded so the ROM that appears in slot 15, usually basic, also appears in slots 11, 7 and slot 3. Likewise the ROM in slot 14 also appears at 10, 6, and 2. etc. The OS is wise to this partial decoding and ...
by Coeus
Thu Feb 08, 2018 11:29 am
Forum: software: other
Topic: BASIC weirdness
Replies: 9
Views: 305

Re: BASIC weirdness

Slightly beside the point, but that's still asking for trouble... Yes, the example is not good production code but was just the first thing I thought of to demonstrate the point. One would not normally have a fixed value (2048) in there either but I put it there to give an idea of the size. One wou...
by Coeus
Wed Feb 07, 2018 10:21 pm
Forum: hardware
Topic: Open Source Logic Analyzer Experiments
Replies: 132
Views: 5879

Re: Open Source Logic Analyzer Experiments

marcusjambler wrote:Pulse view is capturing data but theres no native 6502 decoder...
I guess thats my next job.


I thought hoglet's 6502 decoder started as a plugin and migrated to stand-alone. Could it migrate back again?
by Coeus
Wed Feb 07, 2018 10:19 pm
Forum: off-topic
Topic: Why did CISC prevail?
Replies: 17
Views: 397

Why did CISC prevail?

When designing the ARM Steve Furber was saying how the other processors of the day could not effectively use the available memory bandwidth and this was part of the rationale for simpler, faster instructions, i.e. RISC. RISC took off - all the Unix workstation manufacturers went for it, it was only ...
by Coeus
Wed Feb 07, 2018 10:09 pm
Forum: off-topic
Topic: CPU International Crisis - Are We All Doomed?
Replies: 18
Views: 717

Re: CPU International Crisis - Are We All Doomed?

Interestingly, I was querying /proc/cpuinfo on one of my Linux machines (to see how the CPU compared to those in the logical analyser threads) and noticed a new line:

bugs : cpu_meltdown spectre_v1 spectre_v2

I know Linus had some angry words at the time - maybe this is the result.
by Coeus
Wed Feb 07, 2018 10:04 pm
Forum: software: other
Topic: BASIC weirdness
Replies: 9
Views: 305

Re: BASIC weirdness

I tripped over a similar gotcha when testing some code on BBC BASIC for Windows, which allows 65535-character strings. A subroutine was something like: DEFPROCfred($address), and the program kept falling over running out of memory, and in digging away suddenly realised that there was no <cr> anywhe...
by Coeus
Wed Feb 07, 2018 9:48 pm
Forum: hardware
Topic: OS RAM module
Replies: 84
Views: 4952

Re: OS RAM module

Yes or load a patched OS. If new code is needed and more than just changing some constants for start & end of workspace then dumping some rarer used code (e.g. CFS) and trampolining to it in the physical OS ROM would work. More code space & all functionality. The master handles this by spil...
by Coeus
Wed Feb 07, 2018 7:15 pm
Forum: hardware
Topic: BBC controlled CD Jukebox, great find but need the space!
Replies: 49
Views: 2755

Re: BBC controlled CD Jukebox, great find but need the space!

So is this, by any chance, the reason Master motherboards seem more common on eBay that complete masters?
by Coeus
Wed Feb 07, 2018 7:12 pm
Forum: hardware
Topic: OS RAM module
Replies: 84
Views: 4952

Re: OS RAM module

Any OS gurus following this thread? I wonder if it is possible to fairly easily modify the OS to hand out private workspace to ROMs in the OS RAM region instead of from main memory - so filesystems would use it by default and you wouldn't need to patch each FS/paged ROM... just a patched OS (which ...
by Coeus
Tue Feb 06, 2018 6:35 pm
Forum: hardware
Topic: Open Source Logic Analyzer Experiments
Replies: 132
Views: 5879

Re: Open Source Logic Analyzer Experiments

(The reason I as is some of the "cheap" boards on eBay seem to have a different USB ID, which can cause complications.) You remind me of when I connected an FTDI USB/Serial converter to my QNAP NAS to capture the output of an energy monitor and it was detected as a UPS. Seems the lazy UPS...
by Coeus
Mon Feb 05, 2018 8:57 pm
Forum: hardware
Topic: MMFS Development and Support
Replies: 732
Views: 39815

Re: MMFS Development and Support

Is this a bug? Yes, I think it probably is. I've just created an issue: https://github.com/hoglet67/MMFS/issues/8 Is this causing you an issue? Dave No, I was actually looking at that code because I wanted to try out JGH's HADFS filing system which piggy backs on other filing systems by using their...