Search found 160 matches

by scarybeasts
Wed Nov 06, 2019 6:36 am
Forum: wanted
Topic: Wanted: Cascade Cassette 50 (Electron)
Replies: 18
Views: 642

Re: Wanted: Cascade Cassette 50 (Electron)

Great to see the final pieces being added to a set! Thanks for sharing the picture :)
by scarybeasts
Fri Nov 01, 2019 5:12 am
Forum: hardware
Topic: 1MHz clocks phase difference causing non-deterministic software execution
Replies: 10
Views: 544

Re: 1MHz clocks phase difference causing non-deterministic software execution

scarybeasts wrote:
Thu Oct 31, 2019 10:34 pm
Does anyone own a Master and a scope? I want to know if this phase shift was "fixed" or not. Perhaps this is an investigation for ABUG South!
.... and also needs testing on some model B issue 7s. All of my results are with an issue 3.


Cheers
Chris
by scarybeasts
Thu Oct 31, 2019 10:34 pm
Forum: hardware
Topic: 1MHz clocks phase difference causing non-deterministic software execution
Replies: 10
Views: 544

Re: 1MHz clocks phase difference causing non-deterministic software execution

So Chris (scarybeasts) which pins were you “‘scoping”? system 1MHz is from ADC (NEC D7002) pin 2. (This is for convenience, it's identical to system VIA pin 25 aka. CLK.) 6845 1MHz is from CRTC (Hitachi 6845) pin 21 aka. CLK, while in MODE 7. The 6502 vs. 6845 2MHz signals are also out of phase. At...
by scarybeasts
Thu Oct 31, 2019 9:29 pm
Forum: hardware
Topic: 1MHz clocks phase difference causing non-deterministic software execution
Replies: 10
Views: 544

Re: 1MHz clocks phase difference causing non-deterministic software execution

Try changing the clock rate in the ULA fast->slow->fast. You might be able to get the 1MHz CLK to the 6845 to invert if the timing is right. Different ULA versions might have different behaviour. I didn't get it to invert (and I can't quite imagine how it would), but I can generate a funny double-p...
by scarybeasts
Thu Oct 31, 2019 9:25 pm
Forum: hardware
Topic: 1MHz clocks phase difference causing non-deterministic software execution
Replies: 10
Views: 544

Re: 1MHz clocks phase difference causing non-deterministic software execution

Clock signals for the microprocessor are produced by a 16 MHz crystal oscillator (IC43) in conjunction with divider circuitry in part of the video processor (IC6) which produces 8, 4, 2 and 1 MHz signals. The 1 MHz signal coming directly from the video processor is only used for the Teletext genera...
by scarybeasts
Wed Oct 30, 2019 11:01 pm
Forum: emulators
Topic: Request for testers for quick but fascinating test case
Replies: 36
Views: 1514

Re: Request for testers for quick but fascinating test case

In case anyone was interested in why the same machine would differ in behavior from boot to boot, I think I worked it out. I was curious enough to buy a simple scope. Turns out there's a very interesting hardware quirk. I've given the details in this new thread in hardware: https://stardot.org.uk/fo...
by scarybeasts
Wed Oct 30, 2019 10:58 pm
Forum: hardware
Topic: 1MHz clocks phase difference causing non-deterministic software execution
Replies: 10
Views: 544

1MHz clocks phase difference causing non-deterministic software execution

Hi, This hardware thread can be seen as a continuation of the emulator thread: https://stardot.org.uk/forums/viewtopic.php?f=4&t=18001 In that thread, we were testing a little test case that timed an interrupt arriving. We observed a lot a differing results, including similar machines giving differe...
by scarybeasts
Wed Oct 23, 2019 2:39 am
Forum: programming
Topic: BBC b, reading the CRT vertical sync position.
Replies: 13
Views: 1229

Re: BBC b, reading the CRT vertical sync position.

At the recent ABUG Cambridge, Jonathan Griffiths' talk was described his use of this technique in Rocket Raid :-)


Cheers
Chris
by scarybeasts
Mon Oct 21, 2019 11:33 pm
Forum: software: other
Topic: Calculating digits of Pi in Basic
Replies: 37
Views: 996

Re: Calculating digits of Pi in Basic

Yes, paste from clipboard was a big help. But I made the tactical error of pasting the Sharp Basic original and then fixing it up within JSBeeb, instead of working on a master copy and re-importing it. So the other half of the function, copy-from-printer, would be very handy. This was such a good i...
by scarybeasts
Mon Oct 14, 2019 7:33 pm
Forum: software: other
Topic: Calculating digits of Pi in Basic
Replies: 37
Views: 996

Re: Calculating digits of Pi in Basic

Perhaps *SPOOL to the copy/paste buffer, or into a little text area from which one could copy and paste? If not *SPOOL, then capture the RS432 output... for which we need to know some *FX trickery. But wait: the OS supports a printer, and control-B enables it, so how about capturing that output int...
by scarybeasts
Mon Oct 14, 2019 4:23 am
Forum: software: other
Topic: Calculating digits of Pi in Basic
Replies: 37
Views: 996

Re: Calculating digits of Pi in Basic

BigEd wrote:
Sun Oct 13, 2019 10:48 am
I'd like to, but I'd need to type it in... that's a drawback of experimenting in JSBeeb.
What do you think jsbeeb could offer to make this sort of thing easier?


Cheers
Chris
by scarybeasts
Mon Oct 07, 2019 5:47 pm
Forum: emulators
Topic: Request for testers for quick but fascinating test case
Replies: 36
Views: 1514

Re: Request for testers for quick but fascinating test case

It boils down to whether the disc drive ribbon cable is plugged into the disc drive port at power-on or not: Plugged in: 2/1 Not plugged in: 1/1 Changing this (ie. plugging or unplugging the cable) whilst powered on makes no difference to the result, it is the same from power on until the next powe...
by scarybeasts
Sat Oct 05, 2019 5:33 am
Forum: emulators
Topic: Request for testers for quick but fascinating test case
Replies: 36
Views: 1514

Re: Request for testers for quick but fascinating test case

I'll try Station 129 (BBC Model B issue 2) over the weekend, it's currently having a rest whilst its space is being occupied by my 2 A4000s which are being saved for the nation after 9 years of battery leakage in storage. Issue 2!!! What a beauty. Not sure if this picture I found is it or not but i...
by scarybeasts
Fri Oct 04, 2019 3:24 pm
Forum: emulators
Topic: Request for testers for quick but fascinating test case
Replies: 36
Views: 1514

Re: Request for testers for quick but fascinating test case

FWIW on my Issue 4 Beeb, I also get 1/1 Thanks! If you happened to know what type of 6522 VIAs it has, that's also useful information! If anyone had any of these configurations, they'd be super useful to test: 1) More issue 3s, any type of 6522 VIA. 2) An issue 7, with non-Rockwell 6522 VIA (did an...
by scarybeasts
Thu Oct 03, 2019 6:50 pm
Forum: emulators
Topic: Request for testers for quick but fascinating test case
Replies: 36
Views: 1514

Re: Request for testers for quick but fascinating test case

Issue 7 model B 2 CYCLE STRETCH:1 3 CYCLE STRETCH: 1 Thanks Chris. That's definitely different to this issue 3, which is giving an answer of 2 / 1. I must admit, 1 / 1 was not expected, if anything I was expecting 2 / 2. I'll need to go away and think about this. More model B test results welcomed!...
by scarybeasts
Thu Oct 03, 2019 5:51 pm
Forum: emulators
Topic: Request for testers for quick but fascinating test case
Replies: 36
Views: 1514

Request for testers for quick but fascinating test case

Hi, We've uncovered a strange test result on an issue 3 model B that might represent a change in hardware cycle stretching behavior between earlier and later B's. But it's unclear. Anyone able to run a small test on any BBC (issue anything, B, Master, etc.) and share results would be really helping,...
by scarybeasts
Thu Sep 26, 2019 8:15 pm
Forum: wanted
Topic: Wanted: map and clues sheet for BBC Exile
Replies: 7
Views: 586

Re: Wanted: map and clues sheet for BBC Exile

Hi,

Just bumping this thread.

I now have a copy of the clue sheet thanks to a generous gift at ABUG.

So now I'm just looking for a copy of the map. Willing to buy, trade, negotiate emulator features (jsbeeb), donate to the Centre of Computing History, etc.


Cheers
Chris
by scarybeasts
Thu Sep 26, 2019 8:09 pm
Forum: past events & exhibitions
Topic: Acorn World and ABUG meetup, Cambridge 20-22nd September 2019.
Replies: 249
Views: 10524

Re: Acorn World and ABUG meetup, Cambridge 20-22nd September 2019.

Thanks all for the warm welcome and excellent organization / program -- I had a blast.

I left with a real beeb stuffed into my backpack -- interesting times at Heathrow security -- and I will redouble my efforts to better understand the machine for purposes of accurate emulation!


Cheers
Chris
by scarybeasts
Sat Sep 07, 2019 10:30 pm
Forum: software: classic games
Topic: Stryker's Run
Replies: 9
Views: 721

Re: Stryker's Run

Sorry if the original post wasn't clear. No, I already have my own copy of it. The tape is available to download from StH but the disc isn't. So I just wanted an upload of the disc which Bill Carr has provided. Cool. I'll add it to Everygamegoing so it's available for everyone too. The same STH dis...
by scarybeasts
Thu Sep 05, 2019 12:10 am
Forum: emulators
Topic: BBC B hardware mapping extent -- quick tests!
Replies: 15
Views: 545

Re: BBC B hardware mapping extent -- quick tests!

I'm pretty sure b2 gets the video ULA and CRTC wrong (which I must fix!), and I'll now have to check it's doing ROMSEL correctly too... --Tom b2 has ROMSEL correct. jsbeeb is different (and this incorrect), which is what got me asking about this area. Thanks again to everyone who is contributing re...
by scarybeasts
Wed Sep 04, 2019 9:15 pm
Forum: emulators
Topic: BBC B hardware mapping extent -- quick tests!
Replies: 15
Views: 545

Re: BBC B hardware mapping extent -- quick tests!

Rich Talbot-Watkins wrote:
Wed Sep 04, 2019 12:03 pm
scarybeasts wrote:
Wed Sep 04, 2019 9:40 am
?&FE2F=0
?&FE24=0
?&FE20=0
If you're aiming to hit the Video ULA control register and not the palette, that first one should be ?&FE2E=0.
Yes! ?&FE2E=0 is the correct first test #-o


Cheers
Chris
by scarybeasts
Wed Sep 04, 2019 9:40 am
Forum: emulators
Topic: BBC B hardware mapping extent -- quick tests!
Replies: 15
Views: 545

BBC B hardware mapping extent -- quick tests!

Hi, A quick and easy couple of tests to check out a discrepancy between the emulators. Best run on a relatively vanilla model B. 1) ROMSEL mapping On fresh boot, try these three lines and see on which one BASIC throws a fit: ?&FE3F=0 ?&FE34=0 ?&FE30=0 (This test essentially unmaps the BASIC ROM... w...
by scarybeasts
Wed Aug 28, 2019 8:19 am
Forum: emulators
Topic: Giant cursors vs. screen border -- quick test!
Replies: 2
Views: 242

Re: Giant cursors vs. screen border -- quick test!

Thanks! Giant cursors for everyone!
by scarybeasts
Wed Aug 28, 2019 5:38 am
Forum: emulators
Topic: Giant cursors vs. screen border -- quick test!
Replies: 2
Views: 242

Giant cursors vs. screen border -- quick test!

Hi, There's an interesting question of what happens when a cursor starts within the screen border but then keeps going! There's general emulator agreement that the cursor spews outside of the CRTC render area (perhaps because the ULA is mixing it in). But it'd be good to quickly check on a real beeb...
by scarybeasts
Fri Aug 23, 2019 7:28 am
Forum: for sale / freebies
Topic: Freebies for collection at ABUG Sep 2019
Replies: 10
Views: 642

Re: Freebies for collection at ABUG Sep 2019

I'd like to take the Repton Disks off you please if I may. Happy to donate to the Computer Museum or a Charity of your choice in exchange. Best wishes Andy Now both bagged and packed :) Do feel free to donate to the Computer Museum if you're inspired by what they do but there's no obligation attach...
by scarybeasts
Fri Aug 23, 2019 7:24 am
Forum: for sale / freebies
Topic: Freebies for collection at ABUG Sep 2019
Replies: 10
Views: 642

Re: Freebies for collection at ABUG Sep 2019

Dave Footitt wrote:
Wed Aug 21, 2019 7:36 am
Are you sure you don't want to sell any of these? I wouldn't mind Spy Vs Spy on BBC Disc :D
It's now packed with your name on it. It's yours for free. Feel free to buy me a pint if you are so inspired but there are no obligations attached.


Cheers
Chris
by scarybeasts
Fri Aug 23, 2019 2:42 am
Forum: for sale / freebies
Topic: Freebies for collection at ABUG Sep 2019
Replies: 10
Views: 642

Re: Freebies for collection at ABUG Sep 2019

sbadger wrote:
Wed Aug 21, 2019 10:20 am
Would love Palace of Magic please! :D
Now packed, with your name on it :-)


Cheers
Chris
by scarybeasts
Thu Aug 22, 2019 7:26 am
Forum: emulators
Topic: Emulation tests
Replies: 13
Views: 726

Re: Emulation tests

Yeah my main thing about OSWRCH is exactly which output is the machine-readable test info? But I guess in honesty we coudl check everything against a known-good. Or use the *SPOOL thing if that's easy to check for. Would a simple convention do it? e.g. THIS TEST TESTS WHATEVER TESTED ON TOM'S MASTE...
by scarybeasts
Wed Aug 21, 2019 6:24 am
Forum: past events & exhibitions
Topic: Acorn World and ABUG meetup, Cambridge 20-22nd September 2019.
Replies: 249
Views: 10524

Re: Acorn World and ABUG meetup, Cambridge 20-22nd September 2019

I'll be bringing some surplus software to give away -- any ideas what thread I might use to see if anyone wants to bag specific items up front? Chris, start a new thread in the for sale / freebies section, then post a link to your new thread in a post here :wink: Mark Thanks! So here's the freebies...
by scarybeasts
Wed Aug 21, 2019 6:23 am
Forum: for sale / freebies
Topic: Freebies for collection at ABUG Sep 2019
Replies: 10
Views: 642

Freebies for collection at ABUG Sep 2019

Hi, Some freebies, with a catch: I'll be bringing them along with me to ABUG Sep 2019 in Cambridge, event details: https://stardot.org.uk/forums/viewtopic.php?f=25&t=17456 You'll need to collect them in person or have someone there collect them for you. Let me know if you want to grab dibs on any of...