Electron 6502 desolder / socket pics

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myelin
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Electron 6502 desolder / socket pics

Postby myelin » Tue Jun 13, 2017 11:55 pm

After much messing around with a broken hot air rework station, followed by even more messing around with a solder sucker, and finally getting the rework station to function, I managed to get the 6502 out of my Elk:

desoldered_6502_sm.jpg

... and back in again, on a socket! Actually a 28-pin socket with a second hacked-apart 28-pin socket for the last 12 pins, which was a bit fiddly, but worked:

desoldered_6502_in_socket_sm.jpeg

I was sure I had fried something with all that, but the machine seems to be working just fine.
SW/EE from New Zealand, now in San Francisco: http://myelin.nz/
Having fun making hardware projects for the Electron!
So far: 32k flash cart, USB cart interface, 3-cart expansion, Elk PiTubeDirect. Later: Dual ported ram cart.

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DutchAcorn
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Re: Electron 6502 desolder / socket pics

Postby DutchAcorn » Wed Jun 14, 2017 5:56 am

Congrats on the successful desoldering! Was there a higher goal to reach for socketing the 6502?
Paul

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myelin
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Re: Electron 6502 desolder / socket pics

Postby myelin » Wed Jun 14, 2017 7:47 am

DutchAcorn wrote:Congrats on the successful desoldering! Was there a higher goal to reach for socketing the 6502?


The near-term plan is to make an internal upgrade for my Elk so I can have some RAM / flash / mass storage without having to have anything plugged into the back. The 6502 socket is a really convenient place to get access to almost all the expansion port signals.

I'm also interested in getting hoglet's AtomCpuMon working, so I can play around with ideas like buffering video writes so the CPU can run at 2MHz. That's further away though :)
SW/EE from New Zealand, now in San Francisco: http://myelin.nz/
Having fun making hardware projects for the Electron!
So far: 32k flash cart, USB cart interface, 3-cart expansion, Elk PiTubeDirect. Later: Dual ported ram cart.

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myelin
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Re: Electron 6502 desolder / socket pics

Postby myelin » Tue Nov 21, 2017 8:27 am

More pics to come once I get a good one of the whole setup in daylight, but here's a start:

2017-11-installed-in-electron.jpeg

This is my expansion board that buffers everything from the CPU socket out for 3.3V daughterboards. It's working very nicely right now with one big chunky board sitting on top, with a Xilinx XC6SLX25 dev board (miniSpartan6+) and a Raspberry Pi Zero on top of that. Possibly the first CPU socket interface for PiTubeDirect?
SW/EE from New Zealand, now in San Francisco: http://myelin.nz/
Having fun making hardware projects for the Electron!
So far: 32k flash cart, USB cart interface, 3-cart expansion, Elk PiTubeDirect. Later: Dual ported ram cart.

dominicbeesley
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Re: Electron 6502 desolder / socket pics

Postby dominicbeesley » Tue Nov 21, 2017 1:59 pm

Oooh! Another one! I've just started using the xeropage de0nano/fpag adaptor. And have started thinking about another similar idea! Will you be selling them?

D

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Re: Electron 6502 desolder / socket pics

Postby dominicbeesley » Tue Nov 21, 2017 2:02 pm

And is there a way to "take over" the cpu signals i.e. RnW, A, D for DMA?

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myelin
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Re: Electron 6502 desolder / socket pics

Postby myelin » Tue Nov 21, 2017 5:37 pm

dominicbeesley wrote:And is there a way to "take over" the cpu signals i.e. RnW, A, D for DMA?

No plans to sell them, but if you’re happy to solder one up yourself, I can send you a PCB!

I added in the ability to separate A15:13 from the CPU, so you can implement shadow ram by removing the OS ROM and driving A15:13 to 110 (&C000-DFFF) on the motherboard, which frees up the bus. It wires RnW, D, and the rest of A straight to the motherboard though, so you’ll have to use a soft CPU in an FPGA, or have the CPU on a daughter board, to do DMA.

I couldn’t decide exactly how I wanted all the control signals wired up, so I put a CPLD in there to deal with all that, which means you can do whatever you like with RnW, SYNC etc, with the caveat that the socketed CPU sees what the motherboard sees, with the exception of A15:13.
SW/EE from New Zealand, now in San Francisco: http://myelin.nz/
Having fun making hardware projects for the Electron!
So far: 32k flash cart, USB cart interface, 3-cart expansion, Elk PiTubeDirect. Later: Dual ported ram cart.

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Re: Electron 6502 desolder / socket pics

Postby myelin » Tue Nov 21, 2017 6:20 pm

That is... you have full control (within the limits of the CPLD... so if you want to push a 16MHz clock out through the /NMI pin, you could do that), over everything except A12:0 and D7:0. The A and D pins are wired to 74LVC245 buffers, and you have control of the /OE and DIR pins, so you can put a soft CPU on the board that plugs into the expansion connector and have that drive the bus if you like.

Here's a pic of it with an attached FPGA and Pi -- talking to the micro SD card using MMFS, and with the Pi running PiTubeDirect:
2017-11-minispartan_and_pi_on_cpu_board.jpg
SW/EE from New Zealand, now in San Francisco: http://myelin.nz/
Having fun making hardware projects for the Electron!
So far: 32k flash cart, USB cart interface, 3-cart expansion, Elk PiTubeDirect. Later: Dual ported ram cart.

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Re: Electron 6502 desolder / socket pics

Postby daveejhitchins » Tue Nov 21, 2017 7:16 pm

OK . . . Now let's see a photo with the keyboard in place =D> :lol:

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Re: Electron 6502 desolder / socket pics

Postby myelin » Tue Nov 21, 2017 8:13 pm

daveejhitchins wrote:OK . . . Now let's see a photo with the keyboard in place =D> :lol:


Hah! It won't even close with the *single* riser board (two photos up; the one with the CPU on it). I was hoping to be able to make a board that would give me all this stuff (shadow RAM, internal SD, Tube) without running into the keyboard PCB, but getting the Pi in there is going to be challenging, and I'm going to have to get rid of the high-rise programming connectors :)
SW/EE from New Zealand, now in San Francisco: http://myelin.nz/
Having fun making hardware projects for the Electron!
So far: 32k flash cart, USB cart interface, 3-cart expansion, Elk PiTubeDirect. Later: Dual ported ram cart.

JonC
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Re: Electron 6502 desolder / socket pics

Postby JonC » Tue Nov 21, 2017 9:11 pm

When I was much much younger, I wrote to Slogger to suggest that they take the Electron mainboard out of it's case and give it a bigger one (a bit like the master compact), leaving the Keyboard where it was.

Maybe someone could do this as their next project giving you highrise options for your CPU boards. :lol:
Jon
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myelin
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Re: Electron 6502 desolder / socket pics

Postby myelin » Tue Nov 21, 2017 9:41 pm

JonC wrote:Maybe someone could do this as their next project giving you highrise options for your CPU boards. :lol:


Could work! My keyboard extender cable (the rainbow coloured ribbon visible in the pic) has effectively split my Elk into a two box solution, and with a bit of 3D printing it could be made that way permanently :)
SW/EE from New Zealand, now in San Francisco: http://myelin.nz/
Having fun making hardware projects for the Electron!
So far: 32k flash cart, USB cart interface, 3-cart expansion, Elk PiTubeDirect. Later: Dual ported ram cart.


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