Raspberry Pi emulator state of play...

Discussion and advice about emulating the QL on other machines.
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tofro
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Re: Raspberry Pi emulator state of play...

Postby tofro » Sat May 12, 2018 9:43 am

Dave,

what you get with an emulated QL on a Raspberry Pi is just that - An emulated QL on a Raspberry Pi.

Q68 is a different beast: A modern computer running a modernized QLish operating system that was specifically designed and adapted for the box, aligned with the mainstream development in the QL scene.

I think you are comparing apples to oranges. What bugs me most with an RPi is the ambiguity of character that thing has. It can be anything and thus is nothing (The same concern applies to the MiST, BTW). Not a very technical concern, but still my concern.

Tobias


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Dave
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Re: Raspberry Pi emulator state of play...

Postby Dave » Sat May 12, 2018 7:13 pm

Well, yes. And I wasn't trying to gripe about the price of the Q68 either. Sorry if it came off as such.

For a returning QLer just dipping their toes in or for someone experimenting with the QL, the Pi is the lowest cost quick and easy solution.

The thing I do not like about the Pi is that when you have one in an embedded application you always just see...... A PI. That organization of connectors. The clunkiness of how they're all crammed in on the board edge. The Q68 suffers badly from this too. Both could have been designed as longer, thinner boards with most connectors along one edge. The Pi also has advantages of being designed by a large team of experts for mass production for education with slim margins, whereas the Q68 was designed tersely and minimally.

This is why I was so happy to discover the Pi CM3 (Compute Module 3) a few months ago... It is a Raspberry Pi on a DDR SIMM. It's *tiny*. It just has the CPU, RAM, eMMC, and optional WiFi/BT on the SIMM. You provide a SIMM socket and the connections you want, where you want them. Best of all, ALL the pins are brought out to the card edge, so you have access to many extra pins for extra GPIOs, two UARTs, all the raw video signals (it can do raw RGB)....

It's ideal for high value embedded applications. And you can design a board to fit it into say a QL, where that board would cost less than just buying all the cables and adapters to make it work.

Finally, it supports two displays, two SD cards, and a bunch of things the full Pi cannot support.


Derek_Stewart
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Re: Raspberry Pi emulator state of play...

Postby Derek_Stewart » Sun May 13, 2018 9:36 am

Hi Dave,

It does sound like you are complaining about the price of the Q68. If you think it is too expensive, return the Q68 and I will refund the money paid.

I do not think the Q68 should be compared to the Raspberry PI, as with the Q68 there is 1 hardware developer and 1 operating system developer, where as with Raspberry PI world there are many hardware and software developers who actual seem to get along and do not constantly complain about everything.

I have Raspberry PI 1,2,3, Zero (without Camera Connector), they are not really used so much as the QL hardware.

The Q68 is no way near to the Q40, it is more in between the SuperGold Card and the QXL.

Your maths must be suffering from an Intel or Apple bug...


Regards,

Derek
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Dave
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Re: Raspberry Pi emulator state of play...

Postby Dave » Sun May 13, 2018 10:01 am

I’m not even going to dignify that with a response.


Derek_Stewart
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Re: Raspberry Pi emulator state of play...

Postby Derek_Stewart » Sun May 13, 2018 2:35 pm

Hi,

Okay, but just emphasis, the point, the Q68 comes with a money back guarantee.

Also I do not think it is fair to compare a Raspberry Pi 3b 1.2Ghz Quad core to the Q68 40Mhz single core.

I have both but prefer the Q68.

But Rapberry Pi runs Amibian Amiga Emulator and Riscos very nicely.

I would still like a RPI co-processor on the QL, but this maybe impossible.


Regards,

Derek
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Dave
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Re: Raspberry Pi emulator state of play...

Postby Dave » Sun May 13, 2018 7:29 pm

Derek_Stewart wrote:I would still like a RPI co-processor on the QL, but this maybe impossible.


I experimented with this, and couldn't get the RPi to work on a bus over ~350khz. However, if D0..D7 were serialized, or if everything decoded as a write within a small decoded range was dumped into a FIFO, the RPi could follow what changes were happening within a small block. That block was really limited to the size of the FIFO though. 32K FIFOs are ridiculously expensive. And you'd need three wide, to capture D0..D7, and A0..A14.

If you ignore video and just want to pass data to the Pi and back, a 512K SRAM behind a logical gate (like the 8301 and video RAM) would allow you a flexible amount of each way data transport. Code on the Pi and QL could work out if it was intended for ethernet, display, USB, etc. Realistically, though, in that case you don't want a Pi 3, as you need more GPIOs. If you're just looking for a co-processor, the CM3 is ideal.

So, not impossible but impractical.


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Peter
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Re: Raspberry Pi emulator state of play...

Postby Peter » Tue May 15, 2018 2:55 pm

Dave wrote:This is why I was so happy to discover the Pi CM3 (Compute Module 3) a few months ago... It is a Raspberry Pi on a DDR SIMM. It's *tiny*. It just has the CPU, RAM, eMMC, and optional WiFi/BT on the SIMM. You provide a SIMM socket and the connections you want, where you want them. Best of all, ALL the pins are brought out to the card edge, so you have access to many extra pins for extra GPIOs, two UARTs, all the raw video signals (it can do raw RGB)....

It's ideal for high value embedded applications.

I find it far from ideal, because many of those, especially industrial, require ethernet and a decent realtime interface.

In case of this module, ethernet must be added externally via USB, not nice.

Also, it lacks a fast external bus interface with predictable delay, like a simple parallel bus. One has to resort to SPI, which is reported to have far lower throughput than the clockrate allows. Or something like SMI which is not officially existing and you never know how long it will be there.



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