OSI 502C A custom 502 board design

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MK14HAK
Posts: 356
Joined: Wed Mar 16, 2011 1:49 am
Location: New Zealand

OSI 502C A custom 502 board design

Post by MK14HAK »

For some time I've wanted a 505 board but lately I think the 502 has such great potential for upgrading and in conjunction with a 470K and 582 etc would make a better system by providing both BASIC in ROM and OS65D capability.
There have been many great mods by users in the past detailed in Aardvark and Peek journals etc. that would be worth taking a look at.

Here's a few ideas for starters:


Remove all 2114s and use cache RAM * (470K already has ? ) Frees up a large space on PCB
4K MON ROM decoding (OSI systems memory map reqd) Simplify address decoding for Cegmon.
ACIA cass @ DCXX ?? not FC00
Baud rate options
1/2MHz CLK
8K BASIC in single ROM (additional 28pin skts configurable 2K,4K 8K) More free PCB space
Additional ROM space decoded 8000-A000 - Premier extensions USER, Exmon etc ( ROM/RAM option)
ROM @ E000 (OSI systems memory map ?)

Additional 6809 based 502C
Multi processor capability for 6809/6502 502Cs sharing I/O

Edits:

PIA + AY3-8910 Sound support + Amp and DAC sound mix.

Obviously this requires a good knowledge of the OSI system wide memory map which would be good to document as well.

Mike
Last edited by MK14HAK on Sat Feb 18, 2017 3:41 am, edited 1 time in total.
600RevB:16K,2MHz,64x32,470,CEGMON
SuperKit:502,540B,542B,CEGMON, 8" and 5" FDDs
Cards:PE IO,6522 D-A-D, AY3-8910,ProgramGraphics,Color,UK101
WIP:HexDOS,FDD Emulator
Klyball
Posts: 230
Joined: Tue Dec 09, 2014 12:53 am

Re: OSI 502C A custom 502 board design

Post by Klyball »

You can basically do that already with the 470 you can mix and match ram and rom over the entire 64k space , i put decoding for a11 and a10 on there but you could add a couple of switches instead for even more options i.e switch in out basic , i set mine to switch for cpm or 560z support
Replica 600 Rev D:8K,CEGMON
Replica 610 Rev B: 24k,MPI B-51 with Custom Data separator D-13
510 on the bench/replica 582 backplane/replica 470a /replica 555/original 570B/2 x Shugart 851
Ongoing : 630 ,620 ,510,542c,custom 590,SA1200,592,594,596,598
Steve Gray
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Location: Markham, Ontario, Canada
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Re: OSI 502C A custom 502 board design

Post by Steve Gray »

I'm all for it. I think there is a need (or want) for a single board that can replace all the typical boards one would need for a complete system. I'm not sure if that is totally achievable though. I think the video output is the problem. With everything else it's fairly easy to replace ram and rom with newer single-chip substitutes. You can also replace most of the discrete components with some type of programmable logic (CPLD or PLA) to reduce chip count. Once chip count is reduced you can start adding features like dual or triple processor, floppy controller, sound chip, whatever.

I suppose we could also re-do the video using CPLD. It would be nice if there was one video board that could either be configured manually or via software to emulate the various OSI video modes - 32x32 mono, 64x32 colour, 48x16 and/or other modes that have been hacked via mods.

Last year I learned Kicad and built some boards. My Kicad skills are good, but I'm still learning the electronics theory etc. I decided to make a PCB for Grant Searle's MicroUK-101: http://searle.hostei.com/grant/uk101/uk101.html

I made some mods and routed everything but have not actually sent it out to get produced yet. Info is on my web page is here:

http://www.6502.org/users/sjgray/projec ... index.html

Check it out. If anyone with the electronic knowledge can verify the design it would be appreciated. I'm on the fence as to sending this out as-is, or adapting it to be more OSI-like, with maybe an expansion port or additional IO chips, etc... I'm also open to collaborating with others with good ideas.

Steve
C4P working, C1P working. 600D Replica working, C4P+D&N floppy not working. 505 board, 610 board, Mittendorf board, TOSIE hacker board need testing, PicoDOS disk untested.
Klyball
Posts: 230
Joined: Tue Dec 09, 2014 12:53 am

Re: OSI 502C A custom 502 board design

Post by Klyball »

I think doing it on the superboard foot print might be the way to go, should have enough room to fit it all in and a 3 or 4 slot back plane for original boards

1 osi superduper board
Replica 600 Rev D:8K,CEGMON
Replica 610 Rev B: 24k,MPI B-51 with Custom Data separator D-13
510 on the bench/replica 582 backplane/replica 470a /replica 555/original 570B/2 x Shugart 851
Ongoing : 630 ,620 ,510,542c,custom 590,SA1200,592,594,596,598
MK14HAK
Posts: 356
Joined: Wed Mar 16, 2011 1:49 am
Location: New Zealand

Re: OSI 502C A custom 502 board design

Post by MK14HAK »

Steve Gray wrote:I'm all for it. I think there is a need (or want) for a single board that can replace all the typical boards one would need for a complete system.

Steve
Are you all for a custom 502C ? That's what this thread is about. An updated board to go with existing backplane boards eg 470K 540B 560Z 430B etc. And one for 6809.

I dont want to cram everything on it but there would be room for a PIA -AY3-8910 combination. NO CPLDs etc. Minimum hardware changes and I can get on with 6809 software dev.


Mike
Last edited by MK14HAK on Thu Mar 09, 2017 9:35 pm, edited 1 time in total.
600RevB:16K,2MHz,64x32,470,CEGMON
SuperKit:502,540B,542B,CEGMON, 8" and 5" FDDs
Cards:PE IO,6522 D-A-D, AY3-8910,ProgramGraphics,Color,UK101
WIP:HexDOS,FDD Emulator
Steve Gray
Posts: 321
Joined: Mon Oct 06, 2008 1:54 pm
Location: Markham, Ontario, Canada
Contact:

Re: OSI 502C A custom 502 board design

Post by Steve Gray »

Are you all for a custom 502C ? That's what this thread is about. An updated board to go with existing backplane boards eg 470K 540B 560Z 430B etc. And one for 6809.
Actually i could use a 502/505 combo board with single processor and maximum ram capacity. Selecting floppy or rom basic would be handy, as well as not needing a separate ram card. That would leave 3 slots in a C4 case. One would be for the video board and 2 could be for other boards. Make the board open source so we could adapt it if we wanted.

I would buy a couple boards like this!

Steve
C4P working, C1P working. 600D Replica working, C4P+D&N floppy not working. 505 board, 610 board, Mittendorf board, TOSIE hacker board need testing, PicoDOS disk untested.
Steve Gray
Posts: 321
Joined: Mon Oct 06, 2008 1:54 pm
Location: Markham, Ontario, Canada
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Re: OSI 502C A custom 502 board design

Post by Steve Gray »

Mike,

To clarify, I didn't mean to derail the thread. I think your ideas are great, and I encourage anyone that wants to do OSI projects to do whatever they want regardless of what anyone says.
The great thing about the OSI was the expandability using the OSI buss. If we keep the form factor of the 502 (and similar) boards and reduce chip count we would have a lot of extra
space for sure. I heard OSI made their boards big but with few chips in order to reduce interference or something. These days I think there are methods to pack in more chips more reliably, so I'd like to see some kind of board that is like a superboard, but also has a floppy controller like the 505. I'm not however a fan of the superboard as I prefer a system that can be put in a nice box and with an external keyboard.

So, some comments:
* Remove all 2114 - YES!
* 4K MON ROM - YES, Cegmon is great.
* Yes, the ACIA would have to move
* 1/2 MHz clock - Yes, software select-able if possible
* 8K single rom - Go further--- Single 64K ROM plus 64K RAM with perhaps a PLA to select which is visible, or to completely map out the ROM so we can soft-load the firmware.
* Additional 6809 based 502 - I think the 6809 is a fantastic processor. Coudn't it be included with the 6502 and make them selectable?
* AY3-8910 - Not sure. This chip needs extra support to interface it. Perhaps one of the small Yamaha sound chips would be better. I have a project using a YM2413... it's small and can be memory mapped.

I will offer my services to help with the actual board design. I know Kicad, it's free, and has no board size limitations. If you can make a schematic I can make a board.

Steve
C4P working, C1P working. 600D Replica working, C4P+D&N floppy not working. 505 board, 610 board, Mittendorf board, TOSIE hacker board need testing, PicoDOS disk untested.
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