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avatar_zhulien

Ram and rom, wouldn't it be nice...

Started by zhulien, 13:35, 28 October 22

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zhulien

Quote from: GUNHED on 19:11, 03 November 22Fun thing: What you propose is part of SF2, it has 512 KB ROM - realized using an S-RAM. So to write in this 'ROM' you do actually bank it in a &4000 and then write to this RAM area.

Thinking of a 16 MB RAM expansion, what would it need? Ability of...
- banking in 16 KB of RAM at 0,4000,8000,C000
- banking in 2 KB blocks in every 2 KB step / page of block &8000-&BFFF.
- compatibility mode for current 4 MB expansion
plus the 64kb banked mode, basically the same modes of all DkTronics RAM plus the added flexibility you mentioned above - there can be multiple ways to achieve that - you could even make silly sequences of codes to output to a port like enabling plus features, this could be the plus plus ram feature set.

TotO

It is super easy to add a MMU to bank extra memory into the existing CPC 16K pages layout or to change the chunk size to 64K, 8K, 4K, 2K ... and keep the compatibility. But, there are no reason to do it as programmers will not use, because not CPC standard. :-\
"You make one mistake in your life and the internet will never let you live it down" (Keith Goodyer)

eto

Quote from: zhulien on 01:05, 04 November 22Of course we still need standard 512kb RAM expansions on the market - why not, it satisfies a good minimum useful amount of RAM - and I guess 256kb if it can be made super cheap.
there is no relevant price difference between 256K and 512K if you are using SRAMs. Both require one IC and both IC types are similar price. It could even be that you get the 512K SRAM cheaper than the 256K type. 

eto

Quote from: TotO on 08:37, 04 November 22It is super easy to add a MMU to bank extra memory into the existing CPC 16K pages layout or to change the chunk size to 64K, 8K, 4K, 2K ... and keep the compatibility
just out of curiosity: how much time do you think would need to be invested into the development of such a device? Until it's final, including testing, some basic software to prove it's working and documentation?

Prodatron

It's "just" configuring a CPLD, isn't it?

GRAPHICAL Z80 MULTITASKING OPERATING SYSTEM

eto

Quote from: Prodatron on 10:26, 04 November 22It's "just" configuring a CPLD, isn't it?
yeah....

and probably most of these further steps:

- defining a solution based on requirements and platform restrictions
- research matching components (long term availability and prices)
- design a prototype PCB
- order everything 
- build personal prototype
- test prototype
- fix problems, repeat previous steps if necessary
- design final prototype PCB
- build final prototypes
- send out to testers and collect feedback
- final fixes, probably another PCB
- develop some POC software
- document
- release

My personal gut feeling would be 150-200 hours investment that someone who knows what he is doing has to spend to develop this. And probably a financial investment in the few hundred €. 

I guess it will be easier to find someone, who is willing to invest time and money, if there is at least a PoC of a software that is limited by todays expansions and would truly benefit from a new expansion. 

TotO

Quote from: eto on 10:16, 04 November 22just out of curiosity: how much time do you think would need to be invested into the development of such a device? Until it's final, including testing, some basic software to prove it's working and documentation?
It is the same way that I have explain to you to have 256K DRAM visible by the GA/CRTC by using a 74LS170 or a 74HCT670 to map 16x16K into the 64K address space. :) But using two circuits to be able to address a same amount of memory while reduce the chunks size. Next, it require a bit of configuration (through a CPLD to save room) and to patch the firmware to init the default pages to use (0, 1, 2, 3). I do not plane to do it, I have already done tests into the past. But, I can help you if you want.

What I think, it cost around 50€ and one week. :P
"You make one mistake in your life and the internet will never let you live it down" (Keith Goodyer)

eto

Quote from: TotO on 12:53, 04 November 22But, I can help you if you want.
Oh, thanks for the offer.
But I didn't mean that I am interested in realising this particular expansion. Not in the area of my skills. I was just curious what you think it would require as effort for you as an expert. Seems I was "a bit" off with my estimate and things are much easier once you have the expertise.

TotO

#33
Quote from: eto on 13:20, 04 November 22Oh, thanks for the offer. But I didn't mean that I am interested in realising this particular expansion.
No problem.

For example, with a 8-bit buffer, you can map:

Same memory size:
-  32x 16K = 512K
-  64x  8K = 512K
- 128x  4K = 512K
- 256x  2K = 512K

Same chunks qty:
- 256x 16K = 4096K
- 256x  8K = 2048K
- 256x  4K = 1024K
- 256x  2K = 512K


"You make one mistake in your life and the internet will never let you live it down" (Keith Goodyer)

zhulien

Quote from: eto on 12:02, 04 November 22
Quote from: Prodatron on 10:26, 04 November 22It's "just" configuring a CPLD, isn't it?

I guess it will be easier to find someone, who is willing to invest time and money, if there is at least a PoC of a software that is limited by todays expansions and would truly benefit from a new expansion.
I wonder if a loader for the amazing Alcon 2020 could make it run in such a RAM expansion?

zhulien

forgot to mention, and this is important I think - 1 mx4 card which means I no longer need 2 just for 1mb memory & roms.

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