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"why not use a parallax propeller"


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Why not use a Parallax Propeller 2? 160MHz @ 0.5IPC go zoom.
😄 Well OK I can think of a lot of reasons why,  just thought it was funny this was mentioned in the FAQ at all!
Just for the sake of it, and for completeness, I'll list why I think it'd be a bad idea:
While the P2 could actually handle keeping up with the external bus (It has interrupts unlike the original, with 4 cycles of latency), you've just added a processor that's many, many, many times faster than the main processor and at that point you should just build a P2 computer.
And the good: P2 can do up to 1080p VGA and also handle high quality audio with it's own DACs, which would mean a chip count reduction. Could even repurpose some of it's memory to reduce chip count further by getting rid of some dedicated SRAM.


Anyone know why the Propeller question is even in the FAQ? I was quite amused to see it there.

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27 minutes ago, moony said:

Anyone know why the Propeller question is even in the FAQ? I was quite amused to see it there.

I'm thinking it's because it was frequently asked... ;D

I kid, but yeah, I'm sure it, and any question of the type "Why not use processor/microcontroller ____________?"  Is answered by that question in the FAQ, but reading it again, yeah, it probably has more to do with the VERA than with the 65C02, but all the same, that question is answered in the FAQ.  And at this point in time any questions about hardware are pretty much moot as the specs are pretty well set in stone (or sand/silicon if you will 🙂).

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Posted (edited)

Yes, it is literally a "Question that has been Frequently Asked", especially in the Facebook group before the stalwart design team decided there wasn't anything that fit their requirements and decided to "soft fab their own" with an FPGA approach ... originally the Gameduino, but then the Vera.

To my mind, no matter how well executed, emulating a video chip in software is further from the simulating a video chip in reconfigurable hardware, so I preferred that option anyway, but at the time, a lot of people with experience or, more commonly, who had read about emulating hardware with faster modern microcontrollers for 1-2MHz 6502 designs or 4-8MHz z80 designs didn't grasp how demanding it is to get a software pseudo-register read and write completed in one phase (one half of a cycle) of an 8MHz clock.

Of course, since the Propeller 2 was available for order starting in later 2019 with AFAIU the most current revision available sometime in 2020, the questions were about the Propeller 1. If a P2 cog can keep up with reading and writing pseudo registers on a 8MHz 6502 bus, maybe there is a interesting application or three for a P2 based expansion card, without needing to rely on holding the CPU with the RDY flag.

Edited by BruceMcF
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Oh yes, I do think the P2 could be useful for expansions. It can handle /much/ faster than an 8MHz bus. It's been demoed to do 100MHz+ XSPI (Interfacing with HyperRAM in this case) and similar just fine on one cog. It does feel very overkill, but it may have some interesting applications.

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Posted (edited)

Wow, bazillion is lots.

Essentially boils down to "Why not do <anything except a reasonable attempt at building a retro 8-bit system>?"

 

Edited by rje
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Posted (edited)
On 5/6/2021 at 7:06 AM, moony said:

Oh yes, I do think the P2 could be useful for expansions. It can handle /much/ faster than an 8MHz bus. It's been demoed to do 100MHz+ XSPI (Interfacing with HyperRAM in this case) and similar just fine on one cog. It does feel very overkill, but it may have some interesting applications.

However, if I am hypothetically getting into propeller programming, it is with Tachyon or PropForth, and accessing it over the User Port with the I2C channel as the boot up control channel to set the UserPort access up. So bus access speeds wouldn't be an issue, and I would want one of the much more mature Propeller 1 boards.

Edited by BruceMcF
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On 5/9/2021 at 3:07 AM, BruceMcF said:

However, if I am hypothetically getting into propeller programming, it is with Tachyon or PropForth, and accessing it over the User Port with the I2C channel as the boot up control channel to set the UserPort access up. So bus access speeds wouldn't be an issue, and I would want one of the much more mature Propeller 1 boards.

(1) Anything goes when it comes to the User Port.
(2) I2C rocks.

 

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