stardot.org.uk

Arcadian wrote: ↑

Thu Apr 02, 2020 9:42 am

Hey I've just realised, yesterday was the 10th anniversary of Stairway to Hell's closure (and exactly 21 years since it was founded).

I still use it to grab things to test. Thanks for all your effort -- historic and current, it's much appreciated!


Cheers
Chris

It would be useful if there was a quick and simple way of identifying whether a copy has this bug fixed or otherwise. I have original floppy copies of Repton 3, ATWIFS, LOR and RTT, so would be interesting to see if they have the bug. I wonder if any of the existing disc tool software can output so...

The initial delay before the fungus seems right, I think that came at the request of Steve Botterill who found that if you had a screen with a lot of fungus to start with then it was on your case straight away. He wanted a fungus delay at the screen start so as not to make it too difficult. IIRC th...

It was supposed to be a drop-in replacement, but the early ones (VC2023) had a problem in that they didn't correctly switch settings between teletext and non-teletext modes. To fix that, you had to remove a jumper (S26) and solder a small wire between the VidProc pin 27 (=centre of S26) and one of ...

Hi, [Splitting out from the FSD archiving mega thread: https://stardot.org.uk/forums/viewtopic.php?f=6&t=18668] Finally got my hands on a Tynesoft title with the "interesting" protection -- Winter Olympiad. It has the 5-sector tracks with sectors of 1024, 1024, 512, 256 and 128 bytes. An open questi...

hi Chris, thanks for indepth details of the must be protected *early* disc 8) (as BillC has not confirmed from pg2 :shock: ) your point 4 gave the game away, as mine is a flippy (40 on sideA, 80 sideB) so hence does not need to check for a 40 or 80T drive :idea: here is mine copied using UPURS, jus...

amb5l wrote: ↑

Sat Mar 21, 2020 8:44 pm

@scarybeasts thanks for the lead, I will look at your JS emulator. Am aware of visual6502 and am suitably impressed!

Note that jsbeeb was written by Matt Godbolt, not me. I contributed, including video emulation accurately, later on.


Cheers
Chris

@tricky thankyou that is valuable feedback. I've found a really good post by @kieranhj. It's going to be difficult to achieve cycle accurate emulation of the original hardware but that's one of my aims. And the demos/games you mention will go a long way to proving whether I've managed it. Cycle acc...

The black disk with printed label was a "squeaker" when I attempted to load it, however i managed to catalogue it and it contained !BOOT & Welly and reported 0 tracks. Ok, so it's not possible to tell if a Tynesoft disc is a protected or unprotected version based on its appearance. My black Indoor ...

Ian Botham's Test Match was supplied on a 40track disc with no protection I'm curious whether protected vs. unprotected Tynesoft discs can be distinguished by appearance alone. I have an unprotected Indoor Sports. From the FSD, it looks like your Indoor Sports is protected. What does your Indoor Sp...

Hi, Continuing on my research into BBC disc protections (with an eye on converting @billcarr's FSDs into HFEs as accurately as possible), I'm after Tynesoft disc titles. Which ones? Not all Tynesoft titles have the protection that is particularly of interest. But I believe these do: - Boulderdash (i...

I thought I had seen and heard it all but yesterday I accidentally played Aabatron on the Electron. Not a very remarkable game but the title screen music used the tape relay click as a sort of drum/rhythm sound channel. Any other games or demos that have done that? Also, I'm wondering if this is ba...

Hi, I finally got my hands on a couple of Sherston Software discs (thanks Eelco!) and as promised, I'm reporting back what is actually on the disc surface. Most (but not all) Sherston Software titles are protected by a CRC error on track 39, sector 9. The data in that sector is not deterministic and...

hi Chris, thanks for indepth details of the must be protected *early* disc 8) (as BillC has not confirmed from pg2 :shock: ) your point 4 gave the game away, as mine is a flippy (40 on sideA, 80 sideB) so hence does not need to check for a 40 or 80T drive :idea: Ah interesting. And possibly annoyin...

hi Chris, thanks for indepth details of the must be protected *early* disc 8) (as BillC has not confirmed from pg2 :shock: ) your point 4 gave the game away, as mine is a flippy (40 on sideA, 80 sideB) so hence does not need to check for a 40 or 80T drive :idea: Ah interesting. And possibly annoyin...

Hi Eelco, Thanks so much, this is perfect! I checked these titles against @billcarr's FSD files (hat tip to him!) and they indeed contain the copy protection of interest. There's currently a big thread over on the "archive issues" board titled "Archive of FSD files?" which gets into it. I'll PM you ...

Here you go, I used the HxC Floppy software to explicitly mark up that area as "fuzzy", save it as an HFEv3 and lo! it works fine on the gotek... d. Hmm it did not work for me on the gotek starts loading (CH."BOOT2") seeks to trk 39 and stops there (drive light constantly on)..... That's the protec...

Hi,

I'm researching BBC disc copy protection mechanisms and most of the later Sherston Software titles have interesting things written on the discs. Does anyone have any Sherston Software discs they would consider selling?


Cheers
Chris

Chris, you're completely right - if you look at the blue trace there are still changes in flux, just small and random. If you write 0 flux with a greaseweazle you align all the magnetic domains and write essentially a big string of 0s. You'd have to deliberately write random flux to mimic that, or ...

So, with this, we've ruled that out as what happens, I've read the working floppy back via a greaseweazle from a real floppy drive and you still get the "empty" region. That is interesting, and may not match my experimental observations. I've posted about this in other threads but I'll re-post the ...

Is there a way to convert from/to Kryoflux/FSD formats? No, not directly unless someone writes the software to do it. You can convert kryoflux to HFE for protected or DSD/SSD easily enough though. I think you need to use a real beeb to produce FSDs currently. It's good that HFE is a reasonably capa...

It's no bug in the emulator, essentially. The original would have been weak bits (as per my MFM example, albeit at multiples of the FM bitcell - 4uS). To make sure we're speaking the same language: I would call this fuzzy bits. I'm not sure terminology is 100% standardized here but I follow this: h...

Sorry, I meant FSD :D Happy to zip it up and post it along (let me know) but as Rich said it seems unlikely to help you. My log output gives this for the entire disc: info:disc:FSD: CRC error sector track 39: $27/$00/$09/$01 It's a normal 256 byte sector (both logical and physical), tagged with a $...

It would be really good to get a proper raw dump of Teddy Bears' Picnic, or a similarly protected title, to see what's really going on there. I agree. I've got a setup of suitable drive + scope to see what's actually on the disc surface... but no disc! I would buy one but I haven't found one. If an...

Couple more interesting HFEs attached. Return To Eden is particularly surprising to me because track 0 -- where the catalog goes! -- is crazy. Aside from being just 5 sectors, those sectors are all declared as 512 bytes in the sector header?! Of course, DFS doesn't look at that, it just directly att...

[ITRP] 0492: LDA #$7F [ITRP] 0494: LDX $0490 [ITRP] 0497: LDY $0491 [ITRP] 049A: JSR $FFF1 [ITRP] 049D: LDA #$0E [ITRP] 049F: NOP [ITRP] 04A0: CMP #$0E [ITRP] 04A2: BNE $049D ^ Looks like you've hacked out the test there so that it always loads. LDA #$0E:NOP should presumably be LDA $04A0! Wasn't m...

danielj wrote: ↑

Fri Feb 14, 2020 8:04 am

Yup, good enough for the SCP - that wrote out properly. the HFE you'll need to use v3 to specify a "no flux" region or else work out a way of confusing the FDC.

Just to make sure I understand -- are you saying the written-out Teddy Bears' Picnic disc actually loaded??!


Cheers
Chris

In the HFE it looks formatted - you can see the fluxes... I think v3 will allow unformatted regions? d. It's tricky to spot but at offset 0xf4a00, there are 32 consecutive 0 bytes representing 8 data bytes where all 16 of the FM clock and data bits are 0. I wonder if that is sufficient to carry som...

Not sure - I'll share that SCP so you can have a look at it... Here's what was in your HFE? I'm assuming we're looking at the last sector of track 39? Yes. The first few bytes of the sector actually must be valid (they are executed!) and then the loader expects read-to-read variance a few bytes in....

Fuzzy bits (MFM) from a sherston title: Oh cool, I was very curious as to what's on the disc surface. It's just MFM? Do you have more details? I'd love a raw flux file to study and learn. - Is it valid MFM timing? i.e. are the transitions correctly spaced? - Is it valid MFM encoding? i.e. would an ...