Search found 316 matches

by simonm
Wed Oct 21, 2020 3:27 pm
Forum: off-topic
Topic: Super PSG SN76489 emulator
Replies: 3
Views: 388

Re: Super PSG SN76489 emulator

Yes this is very cool. Upto a point the beeb can poke the SN chip pretty fast probably ~10Khz flat out. In their video the first bit of the SN tune is very doable, requiring sound chip updates in the 50-300Hz range I'd imagine. The second part when the AY is added, not so much - AY is very similar t...
by simonm
Sun Oct 11, 2020 4:05 pm
Forum: for sale / freebies
Topic: For Sale - SmallyMouse2 boards
Replies: 13
Views: 761

Re: For Sale - SmallyMouse2 boards

Seems like the first batch are away, but I'll add my name for another batch if you do make any more!
Cheers, Simon
by simonm
Thu Oct 08, 2020 5:39 pm
Forum: 32-bit acorn hardware
Topic: A310 restoration
Replies: 116
Views: 8717

Re: A310 restoration

Amazing work! :D =D>
by simonm
Tue Oct 06, 2020 1:08 am
Forum: 32-bit acorn hardware
Topic: A5000 repair and the origins of ctrl-g
Replies: 27
Views: 3526

Re: A5000 repair and the origins of ctrl-g

Quick followup - I replaced the CMOS chip and it booted to desktop right away. Lost 5 of 8 pads for the RTC, but managed to jig it so it was anchored to the thu holes for pins 5+6 and 0V for pins 3+4, wires for the rest. There was a lot of battery grot on it when I started, and I worried more traces...
by simonm
Mon Oct 05, 2020 1:58 am
Forum: 32-bit acorn hardware
Topic: A5000 repair and the origins of ctrl-g
Replies: 27
Views: 3526

Re: A5000 repair and the origins of ctrl-g

Some of the things I found during this process: - the monitor type is set to auto if the CMOS chip can't be read. So you can use a normal VGA display to debug. - the floppy drive does not always flash error codes - it can take 34 (!) seconds for the Supervisor prompt to appear with a failing CMOS c...
by simonm
Tue Sep 29, 2020 3:31 pm
Forum: 32-bit acorn hardware
Topic: RISC PC mouse IR LEDs and phototransistors - Rapid discontinuation and some repair tips
Replies: 8
Views: 1180

Re: RISC PC mouse IR LEDs and phototransistors - Rapid discontinuation and some repair tips

This is a really useful post as I have 3 risc pc mice that no longer have any axis movement.
As per the warning above, the Kingbright L-610MP4BT/BD do seem to be unobtainium now. Would anyone have any recommendations for alternative LED/Phototransistor pairs that might work?
by simonm
Sun Sep 27, 2020 12:32 am
Forum: 32-bit acorn hardware
Topic: A5000 repairs
Replies: 57
Views: 2218

Re: A5000 repairs

Great job! =D> Well worth your time - A5000 is a nice machine.
by simonm
Sat Sep 26, 2020 11:04 pm
Forum: 32-bit acorn hardware
Topic: A310 restoration
Replies: 116
Views: 8717

Re: A310 restoration

Lovely - but that gotek makes me weep. SO ugly. I had the same misgivings. As I mentioned above the slot was already carved out by someone else, bit it means a real floppy can always be restored if desired. However, now I've used a Gotek on an Arc its a revelation frankly. It makes the machine a wh...
by simonm
Sat Sep 26, 2020 9:36 pm
Forum: 32-bit acorn hardware
Topic: A310 restoration
Replies: 116
Views: 8717

Re: A310 restoration

Since this came up again recently on Facebook I thought I'd bookend the outcome. I salvaged two of the A310's - one is the "beast" made from all the best bits, A310 ARM3 36Mhz 4Mb, and now with a gotek. The other is a A310 with ARM2, 4Mb. Fortunately the previous owner of one of the machin...
by simonm
Tue Sep 15, 2020 1:26 pm
Forum: 32-bit acorn hardware
Topic: An alternative approach to CMOS/RTC/Battery replacements?
Replies: 4
Views: 473

Re: An alternative approach to CMOS/RTC/Battery replacements?

Interesting to see your wip Dave. You're braver than me, I didn't feel any urge to build my own at all; not least because I dont have any individual components! It's also good to hear a similar solution will work for RiscPC's as I have one of those too, albeit with a missing battery but working RTC....
by simonm
Mon Sep 14, 2020 11:29 am
Forum: 32-bit acorn hardware
Topic: An alternative approach to CMOS/RTC/Battery replacements?
Replies: 4
Views: 473

An alternative approach to CMOS/RTC/Battery replacements?

I've got an A5000 with a poorly CMOS RTC on my workstation at the moment, so I'm considering my repair strategy. I've read with interest the various threads and challenges around replacing the chip - lost pads/continuity checks/battery replacements etc. I also read Retrokit's article about making a ...
by simonm
Sun Jul 19, 2020 5:05 pm
Forum: 8-bit acorn emulators
Topic: Choosing a copyright license for DFS image tool / BBC BASIC de-tokenizer
Replies: 21
Views: 1501

Re: Choosing a copyright license for DFS image tool / BBC BASIC de-tokenizer

For what it's worth I put all of my Beeb hobby projects out as MIT. I have no desire or expectation to profit from or require attribution for them, nor do I have any concerns about how they are used/copied/derived. If they are useful to the wider world, thats just fine with me. I know some projects ...
by simonm
Fri May 01, 2020 1:08 pm
Forum: new projects in development: games
Topic: Untitled Dungeon Game
Replies: 53
Views: 5039

Re: Untitled Dungeon Game

On compression, we've used Exomizer in a lot of our projects. It's fairly fast, and compression ratios are pretty good. Exomizer Homepage here: https://bitbucket.org/magli143/exomizer/wiki/Home Some beebasm ported example code here: https://github.com/bitshifters/bbc-nula/blob/master/lib/exomiser.as...
by simonm
Sun Nov 24, 2019 11:24 am
Forum: new projects and releases: demoscene
Topic: New music conversion - Castlevania III
Replies: 17
Views: 2538

Re: New music conversion - Castlevania III

This is unbelievably good. Never heard anything like it before - amazing stuff! And so many tunes on one disc! =D>
by simonm
Mon Sep 23, 2019 10:31 pm
Forum: 8-bit acorn hardware
Topic: LCD/Modern Display for BBC Master
Replies: 6
Views: 817

Re: LCD/Modern Display for BBC Master

I get the feeling you get what you pay for with these converters, there's quite a few on the market at sub £15 now, but very variable reviews. Seems you need to keep an eye on them supporting RGB input for best quality (as WrightStuff mentioned), plus also watch out for latency in the conversion. I ...
by simonm
Wed Aug 28, 2019 12:10 am
Forum: 8-bit acorn hardware
Topic: A blitter for the beeb?
Replies: 132
Views: 19897

Re: A blitter for the beeb?

Yes indeed, I'm following with great interest, but it is voodoo and magic to me, not sure I have much to contribute other than say that this is very cool stuff :lol:
by simonm
Sat Aug 10, 2019 4:15 pm
Forum: new projects in development: games
Topic: Retro style low-res or not?
Replies: 10
Views: 1677

Re: Retro style low-res or not?

Pixel style aesthetic is evergreen I think. Plus fewer pixels to draw usually means faster frame rate.
If you have the inclination, I'd certainly consider optimizing away from floating point to integer maths as using software fp runtimes is much much slower.
by simonm
Sun Aug 04, 2019 11:51 am
Forum: 8-bit acorn hardware
Topic: Failed RTC chip in the Master 128?
Replies: 10
Views: 1007

Re: Failed RTC chip in the Master 128?

Update on this. Annoyingly, it's held settings for over 4 days on battery backup power now, even though nothing has changed in the machine, so I'm pretty confident the RTC chip is ok now. I now have a horrible and sneaking suspicion one of the batteries wasn't fully inserted since when I was setting...
by simonm
Wed Jul 31, 2019 11:25 pm
Forum: 8-bit acorn hardware
Topic: Failed RTC chip in the Master 128?
Replies: 10
Views: 1007

Re: Failed RTC chip in the Master 128?

Still got 4.18V on IC11 after 2 hours, powered up and config is still ok so far.
Gonna leave it overnight now and see what happens.
by simonm
Wed Jul 31, 2019 9:11 pm
Forum: 8-bit acorn hardware
Topic: Failed RTC chip in the Master 128?
Replies: 10
Views: 1007

Re: Failed RTC chip in the Master 128?

The +5V supply to IC11 (HD146818) has a silicon diode (D8) to prevent the battery from trying to power up the whole machine. Hence when on mains, the +v supply to IC11 will be approximately 0.4V to 0.7V less than the +5V from the PSU. The battery pack also contains a silicon diode to prevent the PS...
by simonm
Wed Jul 31, 2019 6:15 pm
Forum: 8-bit acorn hardware
Topic: Failed RTC chip in the Master 128?
Replies: 10
Views: 1007

Re: Failed RTC chip in the Master 128?

Thanks Mark, so full measures are as follows: Battery pack output - 4.85V Out of the PL connector - 4.5V ON = powered on, OFF = powered off Across Pin 12/24 Vss/Vcc - 4.59V (ON) 4.18V (OFF) Pin 13 /CS - 4.55V (ON) 4.18V (OFF) Pin 14 /AS - 63mV (ON) 0V (OFF) Pin 16 /STBY - 0.3mV (ON) +/- 0.02mV (OFF)...
by simonm
Wed Jul 31, 2019 3:33 pm
Forum: 8-bit acorn hardware
Topic: Failed RTC chip in the Master 128?
Replies: 10
Views: 1007

Re: Failed RTC chip in the Master 128?

danielj wrote:
Wed Jul 31, 2019 3:29 pm
And the voltage is there when you're powered down? (I think that's how it reads but just want to be sure).
Yes.
by simonm
Wed Jul 31, 2019 2:30 pm
Forum: 8-bit acorn hardware
Topic: Failed RTC chip in the Master 128?
Replies: 10
Views: 1007

Failed RTC chip in the Master 128?

I've got a Master 128 that won't preserve CMOS RAM settings and I'm wondering if it's the RTC HD146818AP chip that might have failed. The machine has a replacement 4.5V AA battery pack with inline diode & resistor, brand new duracells and 4.7V measured voltage from the batteries, and this voltag...
by simonm
Tue Jul 30, 2019 12:27 am
Forum: 8-bit acorn emulators
Topic: Sampled sound on the sn76489 -- tests
Replies: 35
Views: 4539

Re: Sampled sound on the sn76489 -- tests

That's great work Tom. Seems as long as the WE bit is in a known state, data can be pumped to the SN chip as fast as it can handle it. =D>
by simonm
Mon Jul 29, 2019 3:06 pm
Forum: 8-bit acorn emulators
Topic: Sampled sound on the sn76489 -- tests
Replies: 35
Views: 4539

Re: Sampled sound on the sn76489 -- tests

Is it the case that all 8-bits of data are presented by the VIA to the SN chip instantaneously - Ie. within one cycle? This would be necessary to ensure the SN never reads partially set data bits/bytes. As an exaggerated example, there were situations from home brew projects using SN76489 with an Ar...
by simonm
Sun Jul 28, 2019 10:39 pm
Forum: 8-bit acorn emulators
Topic: Sampled sound on the sn76489 -- tests
Replies: 35
Views: 4539

Re: Sampled sound on the sn76489 -- tests

P.S. the nesdev forum post says the LFSR register rotates left, but John K's page and Maxim's page say it rotates right... Strong possibility that the nesdev poster meant to type "left [to right]" I wonder? The captures of the white noise sequence that are on SMS page all show an initial ...
by simonm
Sun Jul 28, 2019 3:43 pm
Forum: 8-bit acorn emulators
Topic: Sampled sound on the sn76489 -- tests
Replies: 35
Views: 4539

Re: Sampled sound on the sn76489 -- tests

I personally consider the mystery solved! Those links you shared were very interesting Chris, and I think I've finally reached the same conclusion. There is no scenario in the TI or Sega VDP variants of the SN76489 where oscillations can be stopped or generate a constant output level, they just hav...
by simonm
Sun Jul 28, 2019 3:01 pm
Forum: 8-bit acorn emulators
Topic: Sampled sound on the sn76489 -- tests
Replies: 35
Views: 4539

Re: Sampled sound on the sn76489 -- tests

It's great that even after all these years the level of understanding about these simple components continues to be expanded. Yes, I think this conflicting opinion is a source of a lot of propagation of incorrect information (and emulation!) There's a good source here where someone actually tested s...
by simonm
Sun Jul 28, 2019 3:18 am
Forum: 32-bit acorn hardware
Topic: A310 restoration
Replies: 116
Views: 8717

Re: A310 restoration

Finally came back to this and sorted it out - on closer inspection one of the legs on the new chip wasn't connected properly, so I fixed that and it's all good now. Thanks again everyone. --- In other news, I've acquired a third A310 (yes, I may need counselling :lol: ), which unfortunately is even ...
by simonm
Sat Jul 27, 2019 1:54 pm
Forum: 8-bit acorn emulators
Topic: Sampled sound on the sn76489 -- tests
Replies: 35
Views: 4539

Re: Sampled sound on the sn76489 -- tests

Just a note that I have read conflicting opinion on whether or not setting the tone register to 1 generates a square wave or a constant level. If the chip logic is: decrement counter if 0, flip output bit, reload counter Then we'd expect a 125Khz square wave if the tone register is set to 1. However...

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