48 kB RAM with 3 x 16 kB

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mrtinb
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48 kB RAM with 3 x 16 kB

Post by mrtinb » Sat Mar 24, 2018 1:30 pm

I was thinking about making a small PCB that uses 2 or 3 16 kB RAMpacks to create 32 or 48 kB RAM expansion. Maybe som jumpers could change the settings for the backport to be expansion or straight-thru port.

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Martin
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube

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Paul
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Re: 48 kB RAM with 3 x 16 kB

Post by Paul » Sat Mar 24, 2018 2:10 pm

While this is a funny idea, please dont do it.
the original 16k rampacks draw too much current to have tree of them attached.
And be aware that the bus is not allowed to be like a star because its going to be flooded with reflections. Bus wires need to go go from port 1 to port 2 then to port 3.
Each 16 K rampack wants to be in the 16-32k area. It is difficult to modify the bus in a way that each of the three ports show a different portion of 16 K Adressing while the others will not be adressed.

Its so much easier to create a 56K or even 64K (disabling the ROM as well) RAMPACK with the help of one 64K RAM, 128K RAM 512K RAM chip.

kind regards
Paul
In theory, there is no difference between theory and practice. But, in practice, there is.

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mrtinb
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Re: 48 kB RAM with 3 x 16 kB

Post by mrtinb » Sat Mar 24, 2018 2:48 pm

Thanks for your reply
Martin
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube

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Andy Rea
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Re: 48 kB RAM with 3 x 16 kB

Post by Andy Rea » Sat Mar 24, 2018 4:51 pm

I vaguely remember this been discussed many moons ago on the old ts1000 site... I can't seem to get the search to work 😕 I came up with some fairly simple decode logic and provided you could supply enough power no reason it shouldn't work.

Would be ugly as hell
3 X rampack wobble to contend with
Power usage

When you can use a single ram chip and simple logic , low power consumption, whybwould you not go with a more modern approach

Regards Andy
6 x ZX81, 1 x TS1500 , 1 x +3e, 1 x timex 2040 printer, 1 x timex 2020 cassette deck, siclair printer and some spectrum

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gammaray
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Re: 48 kB RAM with 3 x 16 kB

Post by gammaray » Sat Mar 24, 2018 5:57 pm

If you unpackaged the rampacks they could be stacked in a shallower configuration and back to back. I have project sketches for a stackable adaptation for the bus.

Personally I prefer to try and find out whether it does or does not work meaning find out what is needed to make it work.

Fish paper can be used to isolate the flexible electronics of rampack from each other after they are modified so they can go in same case.

Words of encouragement!
5-TS1000,UK ZX81<-Sheelagh, US ZX81, 2-TS1500/KDLX , 3-TS2040 printer, 2-TS2020 cassette decks, ZXPAND+AY, ZeddyNET, ZXBlast, UDG, ZX8CCB, AERCO, BUILDS/REPAIRS ZX Spectrum, ZX80 Minstrel, ZXMAX48 v1 v2, 2-TS-2068, ROM, 16kRAM

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Re: 48 kB RAM with 3 x 16 kB

Post by Sumila » Wed Mar 28, 2018 8:43 pm

unpackaged the rampacks in back to back with shallower configuration, what you are trying is good. I would like to see your progress in this project. please keep us updates with pictures of your current doing.

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mrtinb
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Re: 48 kB RAM with 3 x 16 kB

Post by mrtinb » Wed Mar 28, 2018 11:17 pm

I was advised not to do it as it will not work.
Martin
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gammaray
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Re: 48 kB RAM with 3 x 16 kB

Post by gammaray » Wed Mar 28, 2018 11:41 pm

I am stoopid enough to try. Making a new decoder...learning the hard way!
5-TS1000,UK ZX81<-Sheelagh, US ZX81, 2-TS1500/KDLX , 3-TS2040 printer, 2-TS2020 cassette decks, ZXPAND+AY, ZeddyNET, ZXBlast, UDG, ZX8CCB, AERCO, BUILDS/REPAIRS ZX Spectrum, ZX80 Minstrel, ZXMAX48 v1 v2, 2-TS-2068, ROM, 16kRAM

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