DIY RAM EXPANSION

[Popopo]

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

[Chr$]

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

[bwinkel67]

This is with the switchable on/off right?

[Chr$]

This is with the switchable on/off right?

Yes.

[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:

Populated it looks like this:

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.

[RalfR]

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

[Chr$]

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

"Slow internal".

[RalfR]

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)

[Chr$]

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?

[tofro]

"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.