DIY RAM EXPANSION

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Popopo
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Re: DIY RAM EXPANSION

Post by Popopo »

So...
Will be there a internal memory expansion? :)
Would be great.


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Chr$
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Re: DIY RAM EXPANSION

Post by Chr$ »

I got some new boards. Just need to populate one and test it out.


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bwinkel67
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Re: DIY RAM EXPANSION

Post by bwinkel67 »

This is with the switchable on/off right?


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Chr$
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Re: DIY RAM EXPANSION

Post by Chr$ »

bwinkel67 wrote:This is with the switchable on/off right?
Yes.


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Ask me about felt pads - I can cut them to size and they have proved excellent for mdv data recovery.
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Chr$
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Re: DIY RAM EXPANSION

Post by Chr$ »

I populated one and pleased to report that it seems to work - Minerva shows 640k with the switch in the up position and 128k with switch in the down position. Board looks like this:
20220728_124025.jpg
20220728_124055.jpg
Populated it looks like this:
20220728_131628.jpg
I haven't extensively tested with any software yet.

Because the info is spread across this topic and the switch is new, components on the board are:

MSK-12C01-07 switch (from German eBay https://www.ebay.de/itm/173613966570 but also on AliExpress)
GAL16V8D
AS6C4008-55SIN RAM chip
Ceramic capacitor 330nF x2
Turned pins (that you have to extract from headers or sockets) x48
Wire and optional header pin to connect to DSMCL (on the right side of resistor R7)

The switch can be accessed through the expansion slot and the QL has to be off when the switch is used.

I can sell some boards for £1 plus postage. I will probably make up a few for eBay - they take a little time to make due mainly to the fiddly aspect of having to extract the turned pins and place them individually.


https://QXL.WIN
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Ask me about felt pads - I can cut them to size and they have proved excellent for mdv data recovery.
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RalfR
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Re: DIY RAM EXPANSION

Post by RalfR »

Looks great! Is this a "fast external" or a "slow internal" memory?


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Chr$
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Re: DIY RAM EXPANSION

Post by Chr$ »

RalfR wrote:Looks great! Is this a "fast external" or a "slow internal" memory?
"Slow internal".


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RalfR
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Re: DIY RAM EXPANSION

Post by RalfR »

Chr$ wrote:
RalfR wrote:Looks great! Is this a "fast external" or a "slow internal" memory?
"Slow internal".
Not possible to make a Fastram (like SQB or Miracle) there? (I do not know, sorry)


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Chr$
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Re: DIY RAM EXPANSION

Post by Chr$ »

RalfR wrote:
Chr$ wrote:
RalfR wrote:Looks great! Is this a "fast external" or a "slow internal" memory?
"Slow internal".
Not possible to make a Fastram (like SQB or Miracle) there? (I do not know, sorry)
I'm a noob of course, but I'm sure that only external RAM can be fast. I suppose there must be other things/signals needed that are only available on the expansion port and it's probably tricky or at least inconvenient to pick them up internally?


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Ask me about felt pads - I can cut them to size and they have proved excellent for mdv data recovery.
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tofro
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Re: DIY RAM EXPANSION

Post by tofro »

Chr$ wrote:
RalfR wrote:
Chr$ wrote: "Slow internal".
Not possible to make a Fastram (like SQB or Miracle) there? (I do not know, sorry)
I'm a noob of course, but I'm sure that only external RAM can be fast. I suppose there must be other things/signals needed that are only available on the expansion port and it's probably tricky or at least inconvenient to pick them up internally?
Well, "fast" memory (rather "non-contended memory") needs a separate data path between the ULA and memory and CPU and memory. As the QL bus is decoupled by the 2 multiplexers, and your memory sits "outside" of the decoupled area, (on the CPU socket), it should actually be "fast" (depending how "DTACK" is generated).

Most internal "slow" expansions were actually piggy-packed onto the internal RAM chips and thus lived in the "shared" access area between CPU and ULA.


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