Real 6502 with 1 MB virtual mode.

[grzeg]

This is very easy in this system .
Apple II is running in one bank 64 kB RAM configured (only RAM), and this I/O is also in RAM.
Apple2 acces to keyboard on 2 ports i/o $C010 (strobe) and $c000 (bufor).
Reading c010 reseting data in c000 . In apple ROM is 2 * reading c010 (bit $c010), Enought replace bit $c010 to jsr C100 ( lda #00, sta c010 rts) and all.
Hardware c64 generates 1/50 s IRQ you need to capture them and switching bank of RAM and move video RAM apple to video RAM VIC
correcting only adress in any line. If in location c000 is $00 (key buf) scan keyboard and key code to $c000. And return from IRQ.
Now I also have c 64, and Apple running, even in several tasks.

[BigEd]

Ah, I see, your IRQ handler is arranging for the I/O to be emulated, and you patched the Apple2 ROM to make that possible.

Very nice!

Cheers
Ed

[grzeg]

changes to the hardware.
1 new address decoder.
2 added an extra register (74ls273 U4) + Multiplexer 74ls257.

The new operating mode transfer from bank to bank.
All read cycles relate to the bank one bank and write to another.
74ls273 U4:
Bit 7 (u4) enables / disables this mode
b0 ... b3 bank to write

[grzeg]

This animation uses a special NUFLI mode and switching tasks.
Due to the intensive use NUFLI mode from the CPU to the normal C64 you can view only a still picture.
With multitasking and switching RAM banks can do full screen animations.
https://www.youtube.com/watch?v=aJ6Qqzl ... load_owner

[grzeg]

the system has been upgraded.
Now it is 16 MB RAM ( 1 simm72 ) 256 banks.
I need data sheet Simm72 64MB or 128 MB

[cr1901]

Forgive me for the stupid question, but in your PDF schematic, why are only 2 wires connected (A8/A9) to the SIMM connector? I think I'm missing something important here.

[Dr Jefyll]

cr1901 wrote:

I think I'm missing something important here.

I know the feeling!

In this case, the photos in grzeg's lead post do a good job of explaining what's going on. The other pins on the SIMM do connect -- to solder connections on the PCB where the original DIP memory ICs previously resided.

-- Jeff

ps: to grzeg: are you aware images can be hosted here on 6502.org as an attachment to your post? You may find this more convenient. Also it ensures they will remain permanently available in future.

[grzeg]

cr1901 wrote:

Forgive me for the stupid question, but in your PDF schematic, why are only 2 wires connected (A8/A9) to the SIMM connector? I think I'm missing something important here.

There already is 74ls173 (DUAL 4-INPUT MULTIPLEXER)
A8 because it really A8 / A18 and A9 => A9 / A19


Pin A10 (the scheme) is connected to ground if someone has applied Simm30 2MB or 4MB, in this case, would work as 1MB.

[Raymond Day]

BigDumbDinosaur wrote:

This seems suspiciously like the scheme developed by Paul Bosaki and described in the August 1989 issue of Transactor magazine.

Just been looking at some messages on this board. Thank you for that link. I have that and one other Transactor magazine. I did the 1MB C=64 only on my 128. Long ago. It works very good. I did 2 of them but the 2nd time I did it nice and neat. Put the RAM chips on top of the other ones and did about the same with the other chips so no board in it. About a year ago no open that C=128 up to get a video of it and posted it on YouTube.

This is what I used long ago to copy the old Q-Link data coming in. On the modem with super snap shot I found one byte that got the data in the RS232 from Q-Link and made a small ML program in every bank and switch between them on got on Q-Link and just went around it knowing it was recording it all in RAM. I did not know when it fill it all up. Did not put that code in it.

I am happy did that because they used that Data to bring back a lot of Q-Link on the Q-Link reloaded.

Remember I spent a hole week putting the modes in the C=128 I still have on my desk now. I was on a vacation when I did it long ago.

From that link I looked at the other Transactor mag Paul Bosacki said he did the C256 just wanted to know what he did before the 1MB one that I went over and over reading it to do it on a C=128. Back then they just Quit the mag and I could not order that one and never got it. But it's on that link. So nice to see it what I wanted to for years and never did.

-Raymond Day