RE: overclocked Sam programs [was RE: ORSAM show report]
Simon Owen wrote: SimCoupe does have some convenience features that aren't true to the real machine, such as turbo mode, fast disk access, fast startup, and auto-booting. Adding support for fixed variable speeds (25%, 50%, 200%, ...) probably falls under the same category, and is something I've got on the ToDo list for a couple of people. Allowing variable CPU speed is a much greyer area, unless it was done in a peripheral-type way like both SAM accelerator prototypes. Yeah, it would be quite a challenge (-- understatement) to try to introduce the same contention issues that Cookie talked about with simcoupe :) G __ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email __
RE: overclocked Sam programs [was RE: ORSAM show report]
Geoff Winkless wrote: And on the subject of the accelerator board, I remember Cookie showing one running Lemmings at the second Gloucester show that someone (can't remember ... was it Nev? don't think so) had built... what happened to that? Well, here's a bit of history... I designed the basic way the accelerator works, and Martin designed the electronics to support it. What it was, was a 8MHz Z80 which I think we overclocked to 10 or 12MHz. The trick to getting an effective accelerator though is this: Most of the time you're doing reads. You don't do writes all that often (I think the ratio was about 1:7 or something like that). So I put in a mirror RAM - nice, fast RAM that the outboard Z80 could use. When you're reading from that RAM, it all happens with no wait states at the higher clock speed - and ignores the SAM's internal RAM entirely. When you're writing to that RAM, it writes to both the internal and external RAM, honoring wait states. IO, of course, needs to honor the waits. Works pretty well - you could actually run Lemmings at 50 frames a second that way. And because most apps sync to the frame sync, it has none of the Turbo Mode problems that PCs had when running on faster processors. Si
RE: overclocked Sam programs [was RE: ORSAM show report]
Just to change the subject quickly, on Ebay currently, I see someone is selling all of their Sam stuff, including 91 games and the machine (currently £16). I have to add that it's not mine! Curiously, whoever is selling it labeled the Sam a Games Console. Not heard it called that before. ;-) As for the accelerator, I think I remember seeing that in action. Am I right in thinking it affected the screen refresh slightly and there was the odd line across the screen, possibly where the ASIC didn't gain access to the video RAM in time? (I'm pretending to know how Simon's design worked!)
Re: overclocked Sam programs [was RE: ORSAM show report]
Geoff Winkless wrote: And on the subject of the accelerator board, I remember Cookie showing one running Lemmings at the second Gloucester show that someone (can't remember ... was it Nev? don't think so) had built... what happened to that? I think it was the second show. I've recently captured the video tape of the first one to MPG and I'll have to find the tape of the second show in order to see if I (or Derek) captured a demo of the Midget. It's funny looking back at the first show because Derek Morgan did most of it and I don't think that he'd used a camcorder before, so there were lots of ceiling and floor shots to edit out. The reason for taking it along in the first place was mainly for screen captures for our Adventure Club mag. The best bit (strangely) is where Cookie, Ian Slavin and Ste Pick where showing off their tee shirts. It was quite colourful. Another interesting bit was where Simon Goodwin was showing Spectum emulation on his Amiga 4000. I think the second show (or was it the third)had a bit of Cookie doing his magician thing. I'll have to try to find those tapes... :) Regards Dave W
RE: overclocked Sam programs [was RE: ORSAM show report]
Andy Chandler wrote: As for the accelerator, I think I remember seeing that in action. Am I right in thinking it affected the screen refresh slightly and there was the odd line across the screen, possibly where the ASIC didn't gain access to the video RAM in time? (I'm pretending to know how Simon's design worked!) Something like that. We weren't handling wait states right because the clock for the external processor and the internal processor weren't sync'ed up correctly. So we were contending the bus when video data was going back and forth. I can't remember if we were also screwing up the data writes, but we might have been. Next step would have been to design a system to handle the differences in the clock, probably using a PAL to do it... That way, the wait states would be correctly honored at the right time, and there would have been no video glitches. Si
Re: overclocked Sam programs [was RE: ORSAM show report]
On Nov 19, 2004, at 11:32 am, Geoff Winkless wrote: Heh. If Andrew's site comes back up in the near future I'll have a play with pyz80, then Statues might still see the light of day :) :) :) Alternatively I might just write the shoot-em-up I always wanted but couldn't be bothered with... It's up now, actually. Now I have to get python :( When was it down? Cheers, Andrew -- --- Andrew Collier http://www.intensity.org.uk/ --- -- Have you lost your Marbles? http://www.marillion.com/
Re: overclocked Sam programs [was RE: ORSAM show report]
[EMAIL PROTECTED] wrote: Howard Price [mailto:[EMAIL PROTECTED] wrote: And on the subject of the accelerator board, I remember Cookie showing one running Lemmings at the second Gloucester show that someone (can't remember was it Nev? don't think so) had built... what happened to that? No Not me. I'm not _that_ clever. Nev.
Re: overclocked Sam programs [was RE: ORSAM show report]
It occurred to me that with SimCoupe we could overclock the machine and code up stuff that wouldn't have been possible on the 6MHz Sam (except possibly with the accelerator board, of course!). Do people think this destroys the heritage of the machine or is it something they'd be happy to see (especially if we did restrict it to what's possible with upgraded hardware)? Hmmm... the temptation would be there to run SimCoupe at higher speeds, and yes great things could be done... but it would lose the feel of the real machine along the way. It's something you seem to hear about occasionally for other platforms - making emulators support extra things the real machine can't, and I feel that just takes the magic away from it all. And on the subject of the accelerator board, I remember Cookie showing one running Lemmings at the second Gloucester show that someone (can't remember ... was it Nev? don't think so) had built... what happened to that? That was Simon Martin Rookyards accellerator, at 8MHz on the day of the show, although Simon did say it got up to 10MHz. What happened to it ... long forgotton in the land of projects not finished... Unfortunately along with Simon and Martin's other projects - the MultiROM, the MiDGET, and dare I say it ... oh go on then. Statues of Ice! Colin = Quazar : Hardware, Software, Spares and Repairs for the Sam Coupe Website: http://www.samcoupe.com/ and http://www.quazar.clara.net/sam/ Issue Ten of Sam Revival Magazine Out Now
RE: overclocked Sam programs [was RE: ORSAM show report]
Colin Piggot wrote: It occurred to me that with SimCoupe we could overclock the machine and code up stuff that wouldn't have been possible on the 6MHz Sam (except possibly with the accelerator board, of course!). Do people think this destroys the heritage of the machine or is it something they'd be happy to see (especially if we did restrict it to what's possible with upgraded hardware)? Hmmm... the temptation would be there to run SimCoupe at higher speeds, and yes great things could be done... but it would lose the feel of the real machine along the way. I don't know - I agree that the feel of the machine would change if you started cheating by adding in direct access to PC hardware or something to get better graphics or sound, but if it's literally just the same but faster (say equivalent to a 12MHz z80) and is achievable with an expansion board on the original hardware, it's no different to having an emulator with support for a hard disk, or a built-in debugger (*cough*, Simon). What happened to it ... long forgotton in the land of projects not finished... Unfortunately along with Simon and Martin's other projects - the MultiROM, the MiDGET, and dare I say it ... oh go on then. Statues of Ice! Heh. If Andrew's site comes back up in the near future I'll have a play with pyz80, then Statues might still see the light of day :) :) :) Alternatively I might just write the shoot-em-up I always wanted but couldn't be bothered with... It's up now, actually. Now I have to get python :( G __ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email __
RE: overclocked Sam programs [was RE: ORSAM show report]
Colin Piggot wrote: Hmmm... the temptation would be there to run SimCoupe at higher speeds, and yes great things could be done... but it would lose the feel of the real machine along the way. I do agree with that aspect of it, in that it only makes sense to emulate features that can/do exist on the real machine. I suppose it could be extended to allow prototyping of upcoming hardware too. Adding features like hardware scrolling support to the emulator would certainly be wrong, IMO! My removing Spectrum emulation from SimCoupe seemed a bit contraversial at the time, but was part of the same philosophy. As well as removing Spectrum-specific initialisation, I tightened up the overall hardware setup to be truer to the SAM (such as the CLUT and ports being zeroed). It doesn't stop you using a Spectrum ROM image, but you'll now need to modify it to set up paging and palette like for a real machine. Besides, there are plenty of dedicated Spectrum emulators out there already that already do a better job :-) SimCoupe does have some convenience features that aren't true to the real machine, such as turbo mode, fast disk access, fast startup, and auto-booting. Adding support for fixed variable speeds (25%, 50%, 200%, ...) probably falls under the same category, and is something I've got on the ToDo list for a couple of people. Allowing variable CPU speed is a much greyer area, unless it was done in a peripheral-type way like both SAM accelerator prototypes. and I feel that just takes the magic away from it all. Agreed. CKay on WoS has a BASIC OS that would be _improved_ by running fast on SimCoupe, but it does still run on a real SAM. I'm not keen on the idea of software that would ONLY run on the emulator. All just my opinion, of course - I'd be interested to hear from anyone that disagrees... Si
