Really large memory expansions - what does it buy me?

[LambdaMikel]

I have a (probably rather stupid) question - what is a really large mem expansion good for? For example, I have a Vortex 512 KB RAM expansion in one of my CPC 464s, and then I downloaded Pinball Dreams, and it would not recognize my memory expansion and didnt start...   This also happened with many other demos that run on the 6128...


I am using plain CPCs, I have no FutureOS or the like. I am curious - what could I be doing with so much memory? I guess I would need SymbOS or FutureOS or the like to utilize it?


I am impressed by rpalmers 2 MB expansion... just not sure what I would be doing with it. Are there any killer applications that require so much memory?

[arnoldemu]

I have a (probably rather stupid) question - what is a really large mem expansion good for? For example, I have a Vortex 512 KB RAM expansion in one of my CPC 464s, and then I downloaded Pinball Dreams, and it would not recognize my memory expansion and didnt start...   This also happened with many other demos that run on the 6128...

Yes the vortex memory expansion is not amstrad/dobbertin/dk'tronics compatible so only very few software knows how to use it.

Demos may not run on your 6128 because of your crtc type??

[SRS]

First: vortex is not compatible like my dk'tornics i.e.
Second the demos may rely on some rom routines / ram layout (where to store colour patterns ... which adress to call for sound ...  i.e.) a 464 just does not have

So what would you need it for ? To say I have a 8bit with 2 MB of course

[LambdaMikel]

Demos may not run on your 6128 because of your crtc type??

I meant to say - they don't run on my CPC 464 with Vortex 512 KB . They work fine on the 6128, but I prefer the 464 for nostalgic reasons 

So it seems I need a DKtronics compatible mem expansion, or rpalmer's.

[Shining]

From the programmer site of view, when you use a 464 with DKtronics compatible, I can use the second 64kB exactly like on the CPC6128. So everything, what is not relying on the different OSses should run without problem.


As far as I understood, rpalmer's expansion will be compatible. Also TOTOs X-MEM is compatible.

[||C|-|E||]

At the moment, not so much software uses tons of RAM, but the possibilities are there    For example, it would be pretty amazing to have a lot of memory and develop a nice point and click adventure that fits completely inside. It would be also great to avoid real time loading in a text adventure like ours by using the RAM as RAMdrive in CP/M. This is not possible with "only" 512KB, but it would be with a 2MB expansion.


Of course, you would need to be able to load your game into RAM fast enough, but you could probably start playing and load the rest of the data in the background if we are talking about a point and click or a text game. Another problem is that a traditional disc drive would probably not be big enough to fill 2MB, even compessing the data. Something like SymbOS connected to a network would probably make the most of it.

[keith56]

Chibi Akumas Episode 2 has a few extra features for 256k systems (DKtronics compatible)
The final boss battle has extra full-screen animated backgrounds... and the cutscenes will have less loading - the game still works on 64k systems without these features

[Shining]

After a hint I've reread the thread about rpalmers memory expansion and as I've read here: http://www.cpcwiki.eu/forum/amstrad-cpc-hardware/2-mega-byte-memory-expansion/msg138861/#msg138861
the expansion doesn't seem to run on 464/664 without modification on the cpc.

So leaves the X-MEM then.

[arnoldemu]

I meant to say - they don't run on my CPC 464 with Vortex 512 KB . They work fine on the 6128, but I prefer the 464 for nostalgic reasons 

So it seems I need a DKtronics compatible mem expansion, or rpalmer's.

yes.

dk'tronics, dobbertin, symbiface 2, x-mem, rpalmer's. All are suitable.

Some do not do 'c3' configuration on 464 so that rules out a few software, some also use additional address decoding to expand past 512KB so *may* fail on some demos but don't let that stop you getting them.

[arnoldemu]

At the moment, not so much software uses tons of RAM, but the possibilities are there    For example, it would be pretty amazing to have a lot of memory and develop a nice point and click adventure that fits completely inside. It would be also great to avoid real time loading in a text adventure like ours by using the RAM as RAMdrive in CP/M. This is not possible with "only" 512KB, but it would be with a 2MB expansion.


Of course, you would need to be able to load your game into RAM fast enough, but you could probably start playing and load the rest of the data in the background if we are talking about a point and click or a text game. Another problem is that a traditional disc drive would probably not be big enough to fill 2MB, even compessing the data. Something like SymbOS connected to a network would probably make the most of it.

or x-mass or other hard disc or sd card interface, but then you may not need as much ram because they load fast.

EDIT: Where can I find a ramdisc for cpc cpm? (2.2, cpm+ or both??)

[rpalmer]

The primary reason why configuration '3' (not just C3, but any configuration with the lower 3 bits = 3)  does not work fully on my expansion (and possibly others) is due to handling of the addresses.

To understand why this is a problem for me, let describe the issue using configuration '3' as I understand it to be:

- Configuration '3' always tells the internal PAL that when it sees addresses &C000 to &FFFF to only swap in the extra 64K memory and access bank #3 at addresses &C000 to &FFFF. This is easy to detect and handle.

- Configuration '3' can also tell the internal PAL that when it sees addresses &4000 to &7FFF to always map them to &C000 to &FFFF and sets the CAS0 active to access the main memory at &C000 to &FFFF. This is where the problems stems from as the complete address is only known when A14/A15 are set by the PAL (see attached part of schematic, in a 6128 the links are not set) at which time my external PAL will always see addresses &C000 to &FFFF.

This means that unless the internal PAL is removed I cannot overcome this issue for a 6128. However a 464 has no internal PAL, so it is possible to overcome which I have not done at this time.

I hope that clears up any confusion.

rpalmer

[||C|-|E||]

or x-mass or other hard disc or sd card interface, but then you may not need as much ram because they load fast.

EDIT: Where can I find a ramdisc for cpc cpm? (2.2, cpm+ or both??)

I will have a look at home, but I am quite sure that I came across a 512KB RAM drive tool when I was coding the adventure. However, since the game is way is bigger than that, I forgot about it

[arnoldemu]

I will have a look at home, but I am quite sure that I came across a 512KB RAM drive tool when I was coding the adventure. However, since the game is way is bigger than that, I forgot about it

I asked the question because I wanted to know if it was possible to patch one of them to go up to 4mb.

[arnoldemu]

I have another question,

The "Extended ram" uses address bits  A8,A9,A10 to select 512KB bank to use.

Is there a standard to define which bits are used for 1mb, 2mb and 4mb?

is a10 for 1mb, a9/a10 for 2mb, and a8,a9,a10 for 4mb?

[rpalmer]

arnoldemu,

I only use A8/A9 since these connect to the PPI and are unlikely to be used by any other devices. This means I can get 4 x 512K of external memory.
Yarek's 4Mb expansion includes A10, but there are devices which use the A10 line as signal for detection of a device (such as an IDE Hard-Disc interface) which means Yarek's memory might not work correctly with other devices.

rpalmer

[GUNHED]

What is using A10???

[rpalmer]

A10 is address line 10, same for A8 and A9.

[GUNHED]

Sure. But a 4 MB expansion does work well and doesn't interfere with other hardware as far as I know (from guys using them).

[gerald]

Just to name a few :
- Amstrad RS232 (A10=0, A8=0, A5=0)  select the SIO,  (A10=0, A8=1, A5=0) select the timer. Both addresss are also valid 4MB memory configuration.
- FDC (A10=0, A8=1, A7=0)
- Amstrad Speech synthesizer (A10=0, A4=1, A0=0)....

There are a bunch of HW using A10, look by yourself : http://www.cpcwiki.eu/index.php/I/O_Port_Summary

[GUNHED]

Thanks! Very interesting!