Stuart Posted June 2, 2017 Share Posted June 2, 2017 Correction, the color board for the Atom was extra... but at least it was an option. Coming from a proud 'Acorn Atom family', I don't recall there being a power switch either. Just had the power lead from the transformer plugging into the jack on the back panel. Quote Link to comment Share on other sites More sharing options...
carlsson Posted June 2, 2017 Share Posted June 2, 2017 A lot of computers (and some consoles) seem to have lacked power switches, like those were not really required and would involve a lot of extra circuitry to install one. The UK computers in particular seem to have been switchless to a large degree: ZX-80/81, ZX Spectrum, Oric-1 & Atmos, Acorn Atom... if it wasn't for being a school computer, I'm sure the Beeb would've lacked a proper power switch as well. Quote Link to comment Share on other sites More sharing options...
+nanochess Posted June 2, 2017 Share Posted June 2, 2017 The isometric games are optimized to update only the changed area of video. So it hides the relative slowness of MSX versus Spectrum. 1 Quote Link to comment Share on other sites More sharing options...
RXB Posted June 3, 2017 Share Posted June 3, 2017 (edited) In the line 40s you've got X=SQR(A). It should be A=SQR(A). That might be the cause of the error you're seeing. Hmm thanks, but that has no effect on the error or the time it takes. Corrected line 40 results RXB: 3 minutes 40 seconds with .00000011 and .009752232 Edited June 3, 2017 by RXB Quote Link to comment Share on other sites More sharing options...
RXB Posted June 3, 2017 Share Posted June 3, 2017 (edited) Corrected RXB: 3 minutes 40 seconds with .00000011 and .009752232 XB : 5 minutes 45 seconds with .00000011 and 6.27999115 Basic: 4 minutes 24 seconds with .00000011 and 1.928494715 Edited June 3, 2017 by RXB 1 Quote Link to comment Share on other sites More sharing options...
JamesD Posted June 3, 2017 Share Posted June 3, 2017 Coming from a proud 'Acorn Atom family', I don't recall there being a power switch either. Just had the power lead from the transformer plugging into the jack on the back panel. Really? Hmmm... I could have sworn I saw a photo of one with a switch on the power supply. I guess it might not have been the factory power unit, or a mod. Then again I've seen so many classic computers it could have been a power supply for a different machine. Quote Link to comment Share on other sites More sharing options...
Asmusr Posted June 3, 2017 Share Posted June 3, 2017 The isometric games are optimized to update only the changed area of video. So it hides the relative slowness of MSX versus Spectrum. Do you know any details about the algorithms they used? Quote Link to comment Share on other sites More sharing options...
+nanochess Posted June 3, 2017 Share Posted June 3, 2017 Do you know any details about the algorithms they used? No. Never had the courage to dive into disassembling it Quote Link to comment Share on other sites More sharing options...
JamesD Posted June 3, 2017 Share Posted June 3, 2017 (edited) Do you know any details about the algorithms they used? The source for Space 1999 on the Oric is available, and at one time there was a detailed pdf on creating the isometric engine. *edit* FWIW, the memory layout use by the 9918 should work out pretty well for this. 3 moving objects would probably require updating less than 100 bytes even in the worst case. Source: http://miniserve.defence-force.org/svn/public/oric/games/Space%201999/ Edited June 3, 2017 by JamesD Quote Link to comment Share on other sites More sharing options...
Asmusr Posted June 3, 2017 Share Posted June 3, 2017 The source for Space 1999 on the Oric is available, and at one time there was a detailed pdf on creating the isometric engine. *edit* FWIW, the memory layout use by the 9918 should work out pretty well for this. 3 moving objects would probably require updating less than 100 bytes even in the worst case. Source: http://miniserve.defence-force.org/svn/public/oric/games/Space%201999/ If it's objects like these from Knight Lore each of them takes more than 100 bytes. But I guess you're right that the VDP transfer is not the limiting factor for isometric games with few moving obejcts . I'm still struggling to understand how the drawing in the off-screen buffer works, i.e. how to determine which of the isometric blocks and sprites you have to redraw when an object moves. Quote Link to comment Share on other sites More sharing options...
artrag Posted June 3, 2017 Share Posted June 3, 2017 (edited) Why not plot all of them from the one with the biggest distance from the screen? Otherwise you need to test 2d collisions among all the objects in the room Edited June 3, 2017 by artrag Quote Link to comment Share on other sites More sharing options...
Asmusr Posted June 3, 2017 Share Posted June 3, 2017 Why not plot all of them from the one with the biggest distance from the screen? Otherwise you need to test 2d collisions among all the objects in the room So in this case (image), if the man if moved you would redraw everything within the orange box? I think that might be too expensive, but it does make a very simple algorithm. Edit: and some of the blocks behind the man would also have to be redrawn. Quote Link to comment Share on other sites More sharing options...
2600problems Posted June 10, 2017 Author Share Posted June 10, 2017 if it lacks a power switch, how would it turn on. stupid question but still Quote Link to comment Share on other sites More sharing options...
Casey Posted June 10, 2017 Share Posted June 10, 2017 Plugging it in would result it being turned on... 3 Quote Link to comment Share on other sites More sharing options...
Frozone212 Posted November 11, 2021 Share Posted November 11, 2021 On 5/29/2017 at 9:41 PM, LASooner said: Anyone who ever, keyed in a program into the ZX81 membrane keyboard for several hours only to knock the 2k ram pack by mistake before it could be saved to tape, would never ask this question. ? 1 Quote Link to comment Share on other sites More sharing options...
Pokeypy Posted November 11, 2021 Share Posted November 11, 2021 (edited) Having had a ZX Spectrum back then, I have to admit that the TI was a very good home computer, with its full typewriter keyboard, sound chip and even 16 bit processor in 1981. Its problems were not of technical, but of business/marketing nature. When Jack Tramiel released the C64 in 1982, he saw the TI as its main competitor and started a price war against the TI. A big argument against the TI was, that Texas Instruments licensed only certain developers to program their proprietary processor and the cartridges (which the developers even had to buy). While the C64 was open to everybody who wanted to program it, so that a large software library was built up over time. Texas Instruments made a big mistake there. In the end that ruined the TI (that was, as mentioned, in itself pretty good), and it was given away cheap. So that customers even wondered, why it was so cheap - was there something wrong with it, maybe? So there you have it: A technically good machine, that nevertheless couldn't compete on the market for other reasons. While the Sinclair machines, although technically maybe not quite as good, were a commercial success, especially the Spectrum. Its system (even with the rubber keyboard, the beeper and the cassette tape as storage device) did make sense and I had a lot of fun with it. The ZX81, well, in my opinion it was too reduced, too limited to be really useful. Similar to the VIC-20 with just 3,5K RAM. But some people even liked these. Well, it were just the predecessors to the machines to come, the Spectrum and the C64. Edited November 11, 2021 by Pokeypy 2 Quote Link to comment Share on other sites More sharing options...
+Vorticon Posted November 11, 2021 Share Posted November 11, 2021 I used to drool over the ads for the ZX-81 in magazines as it was the only computer that seemed to be almost within my financial reach. Ended up (luckily) with a TI console instead (thanks mom and dad!). I do have a complete ZX-81 system now including a ZXpander with SD storage but sadly it has seen very little use lately with only 2 Basic programs to my name (WLANDER and WRACE which I believe are out there). I even keep a portable 5" B&W TV/radio combo just for it. The ZXpander really opens up a lot of possibilities, including a Forth version! 4 Quote Link to comment Share on other sites More sharing options...
GDMike Posted November 11, 2021 Share Posted November 11, 2021 A very drooly forth at that... Quote Link to comment Share on other sites More sharing options...
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