Flipper for Amstrad PCW/CP/M+

[GeoffB17]

Does anyone know anything about a program published for the Amstrad PCW series back about 1989/92 called Flipper. Went through 3 versions, early versions allowed quick flip between LocoScript and CP/M (avoiding the usual need for a total re-boot) and version 3 (I think) extended this to allow for up to 8 'environments' to be flipped between.

To be specific, I'd like to find a copy of the software. I understand the actual prog (Z80 m/c) is fairly small.

Failing that, does anyone know how the system worked - I understand it involved 'tweaking' the normal bank switching processes to create separate blocks, and/or re-assigning blocks normally used for the RAM disk. The system could make use of RAM extensions beyond the usual 512K maximum.

The chap who wrote/published the system, Andy Wilton, is now in NZ working with high level AR/VR systems (re games/movies).

Thanks for any info.

Geoff Barnard

 

[JonB]

Hi Geoff

I'm sure you've been googling around for this but anyway, I found a one line description of what it did on a web page http://simon.mooli.org.uk/LXF/Amstrad/Amstrad.html:

In fact the Z80 CPU addressing limit made it hard for the software to use more than 64K. The extra space in the 8512 was all devoted to the RAM disk. Arguably the hack of the decade was Flipper, a tiny program that turned one PCW 8512 into two 8256s, so you could context-switch CP/M or alternate Locoscript 1 and CP/M without rebooting. Flipper is a classic example of the fact that the value of a program bears no relation to its size.

So from this we might deduce that it has split the 512k of memory on a PCW8256 in half, populated one with a CP/M image and the other with a Locoscript image and implements a means to context switch between the two, probably by bank switching the whole lot. Sounds jolly clever. Seems likely that it loads CP/M first; maybe has a FID based driver to perform the bank switch, because Locoscript also works with FIDs. Note, it must be able to bank switch Page Zero, otherwise it'd need to run Loco in high memory and I doubt it is relocatable.

Not sure how much that helps - I expect you want to use it rather then read about it!

Cheers
JonB

Edit:
Found this on a CPCWiki page that suggests it was a CP/M program:

LocoScript was the only program for the PCW that did not have to be booted from CP/M, as it contained its own firmware (though many supposedly 'CP/M' programs, such as Flipper and RoutePlanner, were in fact very much PCW-specific).

Versions:
Flipper 2 Plus. 3 inch disc. V2.1. 1989. Software Imperative.
Flipper 3. 3 inch disc + manual. Ver.3.06. (9512 only) Software Imperative.
Flipper 3. 3 inch disc + manual. Ver.3.10 (8512 only) Software Imperative.

The key sequence to "flip" was Shift+Alt+Esc

And..
The author has a LinkedIn page too: https://www.linkedin.com/in/andy-wilton-74b504/?ppe=1 - you might be able to contact him directly.