Flipper

[ComSoft6128]

A general question.


"Back in the Nineties"


The PCW utility Flipper allowed for the creation of multiple environments which gave PCW users to operate up to 6(?) programs by "Flipping" between them - this was not multitasking as each program was frozen until it was needed. As far as I know nothing similar was available for the 6128/6128 Plus. Most games for the CPC were written for the 464 - so the ability to flip between say two games on a 128k machine would have been a very nice feature to have. Was this impossible on the CPC? 


I would be interested in your thoughts on this.


Cheers,


Peter 

[AMSDOS]

Most of the programs I'm thinking of to switch programs were Type-ins out of AA. Though later on AA later had a Public Domain which could let you switch programs on their covertape, but I can't think of the name of it.


The type-ins I'm thinking of from AA are the 128k Memory Swapper from AA50 Type-ins which I think is similar to the program AA on their covertape, the author also made the program to support on the 464/664 with the memory expansion and as it resides high in memory it would survive a system reset.
The other program I'm thinking of is more for storing BASIC programs in the extra 64k. As the extra 64k is broken up into 4x16Kb clusters (OUT &7F00,&C4..&C7), 4 BASIC programs of up to 16Kb can be stored there. I'm not sure if this one was meant to be used that way, though that's what it does. I've also got a feeling that someone wrote a similar program earlier which stores BASIC programs in the main 64k, this would obviously mean the programs cannot be all that large though.


CPC Games have a tendency to not allow you to get back to the OS prompt once they are running. I found one AMSOFT game (Blagger), which I think had a POKE to &BDEE,&C9 to disallow anyone to get back to the OS with ESC. There maybe other AMSOFT like this, though the Loader programs are usually Protected if they are in BASIC.

[ivarf]

This sounds just like my Android tablet. It "multitasks" in the same way :/

[andycadley]

The problem with trying to do this on a CPC is that you really need an underlying OS in charge that can switch out the existing program in response to some sort of event and then bring the new one in. But most CPC software isn't system friendly in that fashion, it just pushes all the firmware out of the way, disables system interrupt handling and completely takes over the machine. So the only way to get out of the program is to physically reset the machine, by which point trying to recover state is basically a lost cause.


You could probably do something for BASIC programs, but it would be of limited use in reality and probably not be worth the effort.

[Bryce]

This is the only Flipper I remember from back then

Bryce.

[GeoffB17]

My interest would be solely PCW.


Yes, I heard of the Flipper system long ago, but I never took any interest in it - I understood that it was really aimed at swapping between alternate loads of CP/M and Locoscript on a PCW, and NOT regarding any other environments.


Just tried a search via Google, and there are mentions.


The Flipper system was published by 'Software Imperatives'.   Never heard of them.


The system is referred to on one site as a 'hack', and a 'very small program that demonstrates that the size of a prog has no bearing on it's value' or something like that.


Another source again refers to the prog being designed to get around the usual need to reboot the computer when changing between LocoScript and CP/M.   Flipper allows both systems to be loaded with split RAM, and a hot key allowing you to flip between them.


So, I assume you need enough RAM to provide two viable environments.   I'm not sure this would be possible for MORE than two systems?   Or, if it would be possible to have, say, two CP/M systems loaded for swapping?


More info would be appreciated.   Interesting to see the code, the implication is that the system is a fairly simple 'hack' to exploit the banking within the PCW.   Maybe reducing the RAM available for the RAM drive?


Geoff

[ComSoft6128]

Ha Ha - Bryce I had you down as more Metal Mickey than Flipper.


Geoff - have a look at this.
https://archive.org/stream/8000_Plus_Issue_056_1991-05_Future_Publishing_GB/8000_Plus_Issue_056_1991-05_Future_Publishing_GB_djvu.txt


Cheers,


Peter

[GeoffB17]

Thanks for the above.


The info I found clearly relates to Flipper 2.   Flipper 3 allows the extra 'environments', but to go the whole hog looks like you need extra RAM as well.


The review seems to suggest you need to do something with the boot disks as well?


No hints as to just how this is implemented, although there is suggestion that it's all down to how the RAM blocks (pages) are set up.


Geoff

[ComSoft6128]

Thanks for the replies,
They certainly helped clear that up.


Cheers,


Peter

[Nich]

A general question.

The PCW utility Flipper allowed for the creation of multiple environments which gave PCW users to operate up to 6(?) programs by "Flipping" between them - this was not multitasking as each program was frozen until it was needed. As far as I know nothing similar was available for the 6128/6128 Plus. Most games for the CPC were written for the 464 - so the ability to flip between say two games on a 128k machine would have been a very nice feature to have. Was this impossible on the CPC? 

I remember a small program called Flik on an Amstrad Action covertape which allowed you to flip between two programs within BASIC - so you couldn't really use it for games (unless they were type-in listings, I suppose). You can download it from CPCRulez.

[Ygdrazil]

Yes.. FLIK that was the name, I suddenly remembered this also! 

I also recall a typein from a german magazine that did something similar, however it was more advanced if i remember correctly! I typed it in years ago... I will have to browse through my very old floppies.

If I can dig it up I will upload it to the wiki!

/ Ygdrazil

I remember a small program called Flik on an Amstrad Action covertape which allowed you to flip between two programs within BASIC - so you couldn't really use it for games (unless they were type-in listings, I suppose). You can download it from CPCRulez.

[JonB]

I've sent some files to Geoff, including flipper3.sys.


@Geoff: fancy disassembling them?

[SRS]

PS-MTS/128 - from CPC AI 88 12 may be a help. For 6128 but should be expandable for more memory. ASM Source is included in the mag.

[GeoffB17]

Yes, might help???


But, please translate.


PS-MTS/128 - title of article?


AI - which mag is that?


88 = 1988?
12th May - Issue date, I assume.


Geoff

[GeoffB17]

Done some digging.


You prob mean 'CPC Amstrad International'?


Seen an image of the front cover, looks promising.   Not traced any text yet.


Is there any content on line anywhere?


Geoff

[GeoffB17]

Well, not having total success with trying Flipper.


The system certainly works, mind you.


If I boot from the flipper disk, I get to 'launch' Loco 2.   This loads, etc, just as normal, and then sits as in Loco.   If I press the Flip hotkeys (Shift+Alt+Exit) then the load screen comes back, and I can then swap disk and load CP/M.


If I load CP/M 1.4, my original system, then it loads OK just like a normal boot, and everything if fine, and when finished I can flip between Loco and CP/M, just as advertised.


BUT - I've got JonB's uIDE system, and I'd MUCH prefer to be able to use that.


If I try to load THAT version of CP/M, with the .FID file to enable the DOM drives, then - er - No Go!


I get the very initial system message regarding Amstrad CP/M, thru to the size of the RAM disk (96k ONLY), and then I should get the message about the extra drives, but NOTHING happens.   The 'launch' just stops, and nothing works.


The process seems NOT to cope with the .FID, or maybe the action of the .FID code requires a bank swap and this just does NOT work.   Anyway, the system locks up, and the only thing to do is to power-off.


The very first time I tried it, something further did happen.   The 'launch' stopped at the same point, but I pressed some key(s??)  and I got the 'flip' prompt, went back to CP/M, and the load DID continue and I COULD access the extra drives, but I've NOT been able to replicate that again, and I've tried all the keks I might have used that first time.


Anyway, there MIGHT be circumstances where CP/M 1.4 could still be useful?


The standard load process is set up ONLY to load Loco, then CP/M.   With a 512k machine, there is not really enough RAM to keep space for a 3rd system.   If you complete the basic launches, then you can use the extra menu options, whereupon you could  - say - delete loco, then launch CP/M again using the manual setting to give a really minimal size, then delete the CP/M you've got, and now re-load CP/M again with a reduced space, whereupon you MIGHT now have enough RAM left to load CP/M again?   In all cases, it's the size of the RAM disk that takes the hit.


I'll keep fiddling, and 'flipping'.   Still MOST interesting to know just how Flipper does what it does!


Geoff