Down-sizing because of retiring. Everything has to go.

[Retired]

Hi
I'm new to this group though not new to 6502.
I've been involved in computing since 1977, and wrote my first 6502 code in 1980.
But the time has come to retire (a bit earlier than planned due to ill health).
And I need to down-size which means finding a new home for my 6502 stuff.
I have had a look at the FAQ and can't see any info about 'private sales', though if it is a problem then please let me know.
Basically what I've got is...
1) Stand-alone 6502 board I designed for my university project many years ago. Complete with 6502 code & circuit diagrams.
2) BBC Model B which I used to 'write the code' for my stand-alone board above.
3) A programming board to program a 2KB battery backed RAM chip. Plugs in to the BBC for programming, then remove the battery backed RAM and insert in to the stand-alone board to use as a 'ROM'
4) Floppy Drive for the BBC
5) Sideways RAM.
6) Maybe a few other bits & pieces.

Both the BBC and the stand-alone board are all up and working! And comprehensively tested.
I've changed the caps in the BBC PSU. Re-seated a few of the ICs in the BBC. Cleaned the power connector for the floppy drive. The stand-alone board could do with a bit of TLC - eg cleaning or changing the IC sockets, etc.

If interested in the stand-alone 6502 board and programming board then please let me know. Likewise the BBC + floppy + sideways RAM, etc.
I can provide more info on any of the above - please ask!
I've done a short video of the stand-alone board working. And I can do some photos.
Regards
Andy

[BigEd]

Hi Andy
I take it you're in the UK, and it would make sense probably only to ship to the UK? Or are you willing to ship further afield?

It would be great to see your video - please share a link if you can. Publishing to YouTube or Vimeo would work, or uploading to Dropbox or Onedrive or iCloud or Google Drive would probably work too.

Likewise, please share any photos - you can do that by attaching to a post here, and that's the best way.

Good to be retiring, not so good to have poor health, of course. Thanks for offering to share your things. And welcome to the forum!

Cheers
Ed

[Retired]

Hi Ed

Hopefully I've added a photo okay.
Photo shows the stand-alone 6502 board.
The battery backed RAM acts as a ROM having been previously programmed on the Beeb.
And the software running the stepper motor was downloaded from the Beeb on to the RAM on my stand-alone board. IE can develop software on the Beeb for the stand-alone board and then download it over the comms.
The idea was for the stand-alone board to control various input & output devices (a bit like the Arduino though I designed my board in the early 1990s).

I'm in NW London.
I'm looking to sell my stand-alone board first. Comes with the programming board, stepper motor + PCB and software. Could ship it abroad I suppose though depends where to.

My old Beeb + floppy drive + Sideways RAM (all tested and working), I can sell with the above stand-alone board or separately. But only ship within the UK. Or collect from NW London (where I could do a brief demo).

I'm open to reasonable offers! I have one opinion on value via PM of £200 just for the Beeb, floppy, sideways RAM.

I've never used YouTube, etc so would have to email the video to anyone who is interested in seeing it.

As mentioned the board needs some TLC. Cleaning sockets, etc.
PSU top left corner of photo isn't included.

Regards
Andy

BigEd wrote:

Hi Andy
I take it you're in the UK, and it would make sense probably only to ship to the UK? Or are you willing to ship further afield?

It would be great to see your video - please share a link if you can. Publishing to YouTube or Vimeo would work, or uploading to Dropbox or Onedrive or iCloud or Google Drive would probably work too.

Likewise, please share any photos - you can do that by attaching to a post here, and that's the best way.

Good to be retiring, not so good to have poor health, of course. Thanks for offering to share your things. And welcome to the forum!

Cheers
Ed

[Retired]

I've added a photo of my old Beeb with the programming board.
The programming board is for the 2KB battery backed RAM which I used as a 'ROM' in my stand-alone board.

I soldered ribbon cable to the motherboard and a ZIF socket the other end.
Can have either the programming board or the sideways RAM in the ZIF.

And the control lines which are soldered to the Beeb motherboard have been taken to a IDC socket attached to the Beeb casing.
An IDC connector comes from the programming board (likewise the sideways RAM has an IDC conn), and simply just plugs in to the connector attached to the casing.

Makes it real easy to change between the prog board and sideways RAM.

Please ask any questions......
Thanks
Andy

[Chromatix]

An interesting little collection of equipment, indeed. And the battery-backed RAM card is a pretty decent way of bootstrapping a machine, if you have a second working machine to start with. I think most modern SRAMs are capable of retaining data down to 1.8V, which can be obtained from a button cell via an ordinary silicon diode to prevent reverse current into the cell.

If you built it in the 1990s, I imagine you used a CMOS version of the 6502 in the SBC. The photo is a bit indistinct, but there's a pretty clear Rockwell logo on the chip to the far right. Am I barking up the wrong tree?

[Retired]

I haven't got the board in front of me but from my project report I wrote at the time, I used an NMOS 2MHz 6502
I think the 6522 is on the far right of the board. And the 6502 in the centre.

The battery backed RAM is actually an IC rather than a card. It's plugged in to the ZIF socket on the stand-alone board.

Is it of any interest to you?
Comes with my project report, instructions, software, etc.

Regards
Andy

Chromatix wrote:

An interesting little collection of equipment, indeed. And the battery-backed RAM card is a pretty decent way of bootstrapping a machine, if you have a second working machine to start with. I think most modern SRAMs are capable of retaining data down to 1.8V, which can be obtained from a button cell via an ordinary silicon diode to prevent reverse current into the cell.

If you built it in the 1990s, I imagine you used a CMOS version of the 6502 in the SBC. The photo is a bit indistinct, but there's a pretty clear Rockwell logo on the chip to the far right. Am I barking up the wrong tree?

[1024MAK]

Ahh, so the SRAM is one of the RAM DIL modules with an internal integrated back-up lithium cell. Presumably like the RTC DIL modules that you could also get.

Mark

[Retired]

I've added a close-up photo of the main ICs.
From left to right....
6502
RAM
ROM (battery backed RAM)
6522

Yes RAM DIL with integrated lithium battery. And still working after 25 years!
Regards
Andy

1024MAK wrote:

Ahh, so the SRAM is one of the RAM DIL modules with an internal integrated back-up lithium cell. Presumably like the RTC DIL modules that you could also get.

Mark

[BigEd]

(I should note, that while I find this an interesting display and thread, I'm not a prospective buyer. It might be worth mentioning it on stardot, which is Acorn-centric and has a large UK contingent. There's a for-sale subforum:
https://stardot.org.uk/forums/viewforum.php?f=8
)

[Retired]

Thanks Ed,
I've already registered for stardot (as someone else had already suggested it was a better place to advertise BBC Micro stuff).
BTW I have a few Beeb items on eBay. Including an Epson dot matrix printer - tested and working.
https://www.ebay.co.uk/sch/sherlock_ohm ... =12&_rdc=1

Regards
Andy

BigEd wrote:

(I should note, that while I find this an interesting display and thread, I'm not a prospective buyer. It might be worth mentioning it on stardot, which is Acorn-centric and has a large UK contingent. There's a for-sale subforum:
https://stardot.org.uk/forums/viewforum.php?f=8
)

[Chromatix]

I might possibly be interested in the SBC, as a way to help bootstrap my own efforts, but I'm away from home for the next couple of weeks - indeed, on the wrong continent entirely. I'll get home to Finland in nearly two weeks' time.

[Retired]

Hi
It will be a good price! I know I have to down-size and I would like to go to someone who will use it.
Will you contact me when you are back in Finland?
Regards
Andy

Chromatix wrote:

I might possibly be interested in the SBC, as a way to help bootstrap my own efforts, but I'm away from home for the next couple of weeks - indeed, on the wrong continent entirely. I'll get home to Finland in nearly two weeks' time.

[Retired]

Hi Chromatix
I've added a photo of my SBC and all the bits that go with it.
To the right is the programming board for the battery backed RAM (being used as a ROM).
At the top is the stepper motor and driver board.
And then the SBC itself.
All sitting on my project report. Over 100 pages of description, info, circuit diagrams, datasheets, etc.
The SBC has a 5v regulator on board so needs power of about 9 or more volts.
Regards
Andy

Chromatix wrote:

I might possibly be interested in the SBC, as a way to help bootstrap my own efforts, but I'm away from home for the next couple of weeks - indeed, on the wrong continent entirely. I'll get home to Finland in nearly two weeks' time.

[Chromatix]

Well, I'm back on the right continent at least. Actually I'm in the UK for a few days, but probably not long enough to visit anywhere else or receive a delivery.

Interestingly, the M48Z02 battery-backed NVRAM you used seems to still be in production; Mouser has it for €9 or so. The modern versions have -7, -15 and -20 speed grades; your -25 speed grade is no longer listed in the datasheet. What it does have is a procedure for checking the internal battery health; if the voltage appears low when main power comes up, an internal flag is set which blocks the first write. So you can verify the health using something like:

Code: Select all

LDA $FFF0 ; some non-critical byte
EOR #$FF
STA $FFF0
CMP $FFF0 ; did the write succeed?
BNE BadBattery
EOR #$FF
STA $FFF0 ; restore original value
JMP GoodBattery

After the first write, whether or not the battery is okay, the NVRAM functions normally. The only remaining consequence of a failing battery is that it might forget some bits when the power goes out.

[Retired]

Whereabouts are you in the UK?
I'm in London.
It may be possible for me to drop it off if you are not too far away.
Or maybe do guaranteed next day delivery.
Regards
Andy
PS: The NVRAM is still working okay.

Chromatix wrote:

Well, I'm back on the right continent at least. Actually I'm in the UK for a few days, but probably not long enough to visit anywhere else or receive a delivery.

Interestingly, the M48Z02 battery-backed NVRAM you used seems to still be in production; Mouser has it for €9 or so. The modern versions have -7, -15 and -20 speed grades; your -25 speed grade is no longer listed in the datasheet. What it does have is a procedure for checking the internal battery health; if the voltage appears low when main power comes up, an internal flag is set which blocks the first write. So you can verify the health using something like:

Code: Select all

LDA $FFF0 ; some non-critical byte
EOR #$FF
STA $FFF0
CMP $FFF0 ; did the write succeed?
BNE BadBattery
EOR #$FF
STA $FFF0 ; restore original value
JMP GoodBattery

After the first write, whether or not the battery is okay, the NVRAM functions normally. The only remaining consequence of a failing battery is that it might forget some bits when the power goes out.