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Detecting Archimedes vs. newer machines is easy - the MRS & MSR instructions are NOPs in ARMv2, so you can do something like: MOVS R0,#0 MRS R0,CPSR CMP R0,#0 ; NE = IOMD-era, EQ = IOC-era (I'm using MOVS for the first instruction instead of MOV just to guarantee that one of the PSR bits is set - ju...

IIRC "generate 4 different copies of the sprite at different pixel offsets" is the basic approach that was used by FastSpr sprite plotter used by Asylum and Oddball. It's also the approach that I used myself back in the day (not sure exactly where I discovered the approach - probably I just copied w...

(That said, http://armconverter.com/hextoarm/ decodes the EAE00069 instruction as "b #FF8001AC" (I guess b #0x38001AC when you mask out everything above bit 26) when executed at 0, and "b #0x30001AC" when run at 0x3800000, so maybe it will only work when run from 0.) Yeah, B and BL encode the addre...

I was going to link you to the (textless) PDFs that Usborne released a while ago - but on reviewing the thread here on *., it looks like someone's already sorted out a BBC version of Dungeon of Doom:

viewtopic.php?p=131258#p131258

When goto's become ugly/confusing I tend to try and restructure the code into a subroutine, so that the goto's become return's: static inline int cat_name_cmp(const char *nam_ptr, const char *cat_ptr) { const char *cat_nxt = cat_ptr + 16; do { char cat_ch = *cat_ptr++; char nam_ch = *nam_ptr++; if (...

If that's how you choose to interpret it, then I guess it's up to you. Seems you read the first two sentences you quoted but not the third - which clearly (I thought) explained that it was a different focus. I think that wasn't as clear from your last post. I took your "retro OS" comment from one o...

So I'm wondering, what would the development focus be for a "retro" hobby OS version of RISC OS? Are they incompatible with the above, or have I misunderstood you and your "retro" hobby OS is actually my "modern" hobby OS? I think this has been answered already above but just to be direct: It's not...

It would be great if the contributors to this thread could step back and take a breath. Normally the atmosphere here on StarDot is positive and encouraging. Apologies if I brought things down a bit. I know I have been part of "the problem" at times, and in the long run that's never likely to work o...

The only necessity for the DDE is if you want to rebuild the whole ROM. If you really want to develop one of the OS modules, most of them are compilable for softloading, and this is (at least theoretically) possible with GCC. Do ROOL accept GCC code? I was under the impression OS ROM code must use ...

For someone to sponsor a bounty of that size would mean that you'd have to have some sort of viable business model to give you a sizeable ROI that was critical for that bounty to be completed AND be something only RISC OS could do. I can't think of any situation that would make that a long term via...

It was the ROOL talk (or perhaps both talks?)

https://youtu.be/110El6TbMY0?t=1000

Remember that there are still a few closed-source components (at least MbufManager, Resolver and ShareFS). They're on ROOL's list of things to sort out, but until that happens you're going to be left a bit short if you're interested in a fully open-source OS.

I'd be interested in seeing a summary of the differences between MEMC and MEMC1A. It looks like some of the differences are: Improved performance (mostly due to implementing proper fixes for some bugs that MEMC used workarounds for?) Support for chaining multiple MEMC's together to allow for >4MB of...

Nice!

One easy optimisation: Move line 130 down to 165 (or just get rid of the pp variable completely, since it's only used once)

A few factual mistakes: "RSUB R1, R0, R0 shl 6" - the correct mnemonic for reverse subtract is RSB. I don't think I've ever seen an assembler which accepts "RSUB". "You can load only 12 bits at a time, although the constant can be inverted and shifted." - you can only load 8 bits at a time, since 4 ...

There was a "mailing list glitch" recently, so if you don't get any feedback in the next day or two then it's probably worth trying to send it again (or a test message, at least)

http://www.riscos.info/index.php?title= ... itch_fixed

davidb wrote: ↑

Tue Sep 04, 2018 1:50 pm

The Centre for Computing History has put up a few interesting videos related to ARM recently. Here's one that I found quite intriguing: Historic ARM Presentation to Apple Computer - 1992.

Interesting to learn about the genesis of some of the ARM6's features - thanks for bringing it up!

4corn update 12/09/2017

I think you've been spending too long looking at old documents - it's 2018, not 2017!

There's an Iconbar thread with a few examples of Arc games that made it to other platforms. You might need to do a bit of digging to get working URLs, though. https://www.iconbar.com/forums/viewthread.php?threadid=11135&page=3#110631 There's also 1992 Olympics tie-in Quest for Gold, which appeared o...

Somebody knowledgeable about the limitations of floating-point arithmetic wouldn't find them surprising, but they ought to be very surprised by what Acorn's BASICs do with my example! Someone familiar with Acorn BASIC wouldn't be surprised by Acorn BASIC's behaviour either. Horses for courses :) Th...

there are a great many number of unexpected and potentially dangerous things that can go wrong with traditional floating point arithmetic as well. Sooner or later the programmer has to learn that these issues exist. Can you give an example? If you're thinking of the well-known issues associated wit...

Can anybody offer an explanation for why Acorn/Sophie might have felt that such a (superficially) unhelpful behaviour is desirable? The best I can think of is that it was born from a desire to emulate the behaviour of the CPU. The 6502 integer addition/subtraction instructions wrap, therefore BASIC...

My understanding was that on APCS at least 4(?) function arguments/parameters were passed in registers. Yes, the basic approach is that the first four (integer) values are passed in registers, with the rest being pushed to the stack. But there are many different variants of APCS, both for 32bit and...

I haven't looked at the algorithms in any detail, but for current RISC OS versions: SWIs number -> handler lookup is via a hash table (mapping to handlers for each SWI chunk), except for kernel SWIs which use a lookup table for each SWI number Interrupt handlers and vector claimants use arrays (inde...

I don't understand the underlying issue, all I know is that real hard disc images need tweaking a bit to work in RPCEmu.

https://www.iconbar.com/forums/viewthre ... adid=12152

Perhaps someone with more time than I, would like to try it and come up with a list of what the keys do. Not sure if it's true for all versions, but the VOTI release of the designer had a section of the BASIC program that contained a listing of the controls (probably accessible in-editor by pressin...

On the subject of "Unreleased games", were Stunt Racer 2000 Extra Tracks Series 3 or the Stunt Racer 2000 Track Designer ever released? I have both, which could probably be released if someone is prepared to test them to confirm they work. I don't know if the track designer was ever officially rele...

RISC OS 5 Improvements to BASIC 5: (BASIC V) BASIC 1.32 -: https://web.archive.org/web/20111227182632/http://www.iyonix.com/32bit/BASIC.shtml (Archive copy) (I'm not sure what other improvements were made in Risc OS Open..) Conveniently, the "open" part of the name means you can just check the CVS ...

RISC OS BASIC contains code for converting to and from 5-byte and IEEE double precision - if you can decipher the sources. https://www.riscosopen.org/viewer/view/castle/RiscOS/Sources/Programmer/BASIC/s/Stmt2?rev=1.18#l1842 The code at lines 1856-1865 convert 5-byte floats to double precision, lines...

One difference between this and RISC OS 3.71 (which is what I have running in RPCEmu) is that in RISC OS, setting the eigen value to values other than 1 alter the drawing coordinates but the mouse coordinates are NOT changed. In Brandy, both are changed keeping the mouse in step with the drawing. I...