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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 21st May 2021, 6:25 am   #21
ortek_service
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Default Re: 80-BUS Loft treasure?

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<snip> so it's whether the light on the front comes-on that's most important.
Yes, the light comes on when I (double) click on the disk icon and extinguishes when the systems asks me to insert a disk....
Well that seem like it's accessing it OK.
Have you got a spare disk that you can try formatting (to 720KB), so at least the format will be right for that drive.
If you are putting standard 360KB ones into it, then it will not be expecting these, if the system thinks they are 3.5" drives (as 3.5" ones were never less than 720KB)
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Old 21st May 2021, 4:43 pm   #22
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Default Re: 80-BUS Loft treasure?

Quick "Back of Cigarette Packet" calculation: A floppy drive makes 300 rpm. So that's 300 tracks in 60 seconds, which is 200ms for one track. Call it 50 000 bits per track, that's 50 bits in 200µs = 4µs per bit.

It ought to be possible to emulate a floppy drive through the GPIO of a Raspberry Pi, even just about running a program in an interpreted language.
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Old 21st May 2021, 5:03 pm   #23
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Default Re: 80-BUS Loft treasure?

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It ought to be possible to emulate a floppy drive through the GPIO of a Raspberry Pi, even just about running a program in an interpreted language.
The only snag with that is the port structure on the Pi with the GPIO pins mainly not being picked from hardware port bits which are sequential / side by side, meaning that in most cases, to input or output a parallel byte you have to read or write or input the value from or to each port bit in turn which makes parallel communication considerably slower than it could be.

Arduino, when written in the 'proper' Arduino way, also suffers from this one-bit-at-a-time limitation but on Arduinos it is relatively easy to go 'straight to the metal' and access one of the 8-bit wide ports of the underlying micro on an Uno or Mega in one parallel read or write. Doing so breaks compatibility with other Arduino boards but that is not always the most important thing to consider.

However, when looking around for something else recently I did see mention of a Pi-1541 - I didn't follow it up but the name strongly suggests it was a Pi 'being' a Commodore Disc drive.
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Old 21st May 2021, 8:11 pm   #24
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Default Re: 80-BUS Loft treasure?

The CBM 1541 disc drive has its own 6502 CPU, ROM and (expandable!) RAM, interfaced directly to the disc drive mechanism. It isn't even taking any notice of the opto sensor, so you can simply reverse a disc to use the other side. It reads a whole track's worth of data from the disc into its own memory, then selectively transfers just what the C64 asks for over the "488-over-serial" interface.

The Pi1541 plugs into a Commodore 64 and acts on commands sent over the serial bus to the disc drive, presenting any data the C64 asks for on the bus as a real 1541 would.

If a 1MHz 6502 can handle the data rate of a floppy disc, then a Raspberry Pi ought to be able to. Even the issue of not having all bits of a GPIO byte exposed is no hardship, when the bits are coming in serially anyway!
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Old 21st May 2021, 8:15 pm   #25
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Default Re: 80-BUS Loft treasure?

I m actually putting together a Fluxengine which uses the Cypress CY8CKIT-059 PSoC® 5LP Prototyping Kit to interface between USB and the floppy drive. So far I have programmed the interface but I haven't managed to get my XP machine to run Fluxengine....
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Old 23rd May 2021, 7:16 am   #26
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Default Re: 80-BUS Loft treasure?

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The CBM 1541 disc drive has its own 6502 CPU, ROM and (expandable!) RAM, interfaced directly to the disc drive mechanism. It isn't even taking any notice of the opto sensor, so you can simply reverse a disc to use the other side. It reads a whole track's worth of data from the disc into its own memory, then selectively transfers just what the C64 asks for over the "488-over-serial" interface.

The Pi1541 plugs into a Commodore 64 and acts on commands sent over the serial bus to the disc drive, presenting any data the C64 asks for on the bus as a real 1541 would.

If a 1MHz 6502 can handle the data rate of a floppy disc, then a Raspberry Pi ought to be able to. Even the issue of not having all bits of a GPIO byte exposed is no hardship, when the bits are coming in serially anyway!
However, the 1541 only ended-up reading 1 sector per revolution, due to the Serial-IEEE kludge.
But I recall speed could be boosted with alternate turbo version. However, I'm sure this wouldn't max-out a Pi1541, especially if used with a later much-faster Pi.

And the 'GoTek' http://www.gotekemulator.com/ & much-cheaper clones etc. of this Solid-state USB key-drive FDD replacement used a rather slower 72MHz STM32 single-core ARM uC
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Old 23rd May 2021, 2:12 pm   #27
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Default Re: 80-BUS Loft treasure?

Hi Richard,

Follow on from post #15.

I've recapped mine but they are not happy, One now reads and writes but has stopped spinning up to centre the disc when you insert a disc. The other one no disc centreing/reading/writing, it spins up when you try to access a disc but thats it. I'm useing a BBC Master.

I've put a want up for a service manual, I've searched the net but the one I found has a different layout for the logic board than mine

Now would you happen to have a manual?

I'll open a thread on the repair.
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Old 31st May 2021, 12:55 pm   #28
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Default Re: 80-BUS Loft treasure?

Here are some photos:
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Old 31st May 2021, 12:56 pm   #29
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Default Re: 80-BUS Loft treasure?

And a few more:
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Old 24th Jun 2021, 8:07 pm   #30
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Default Re: 80-BUS Loft treasure?

I just thought I would mention that I am probably in a position to create boot disks for CP/M 2.2 (bios 1.4, bios 3.5 and bios 3.4MFB) if that is any help (or encouragement) to anyone.

Quote:
Originally Posted by mole42uk View Post
I was in my loft today sorting out several boxes of old Apple Macintosh stuff (printers, Trinitron monitors, a couple of SE computers, interfaces, keyboards) when I found a box containing several foil-wrapped 80-BUS items:

1. GM812 IVC board
2. MAP80 256k RAM board
3. GM813 Z80 CPU board
4. GM829 FDC/ SASI board
5. DIY EPROM Programmer board
6. Xebec disk controller
7. Shugart 604 5Mb hard drive
8. TEC FB-504 720kb floppy drive
9. A 4U rack-mount case containing a heavy-duty power supply
10. NASCOM 2 CPU board
And varous cables, NASCOM keyboards etc....

I do have most of the user manuals to go with but I have no idea what to do with it all. Any ideas would be most welcome!
I am very keen to archive as much Gemini software as possible, I would love to have a meander through your disks and documentation.

If you havn't seen it already, details of the Gemini systems are here https://glasstty.com along with some resources, Gotek instructions and so on.
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Old 24th Jun 2021, 10:18 pm   #31
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Default Re: 80-BUS Loft treasure?

Although I have decided to sell the hardware, I do still intend to use the floppy drives and try and recover as much of the 40+ floppies that I still have. Much of it seems to be software downloaded from an ancient BBS but there are several disks which are labelled as Gemini specific. I'll try and catalogue them over the next weeks.
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Old 24th Jun 2021, 11:05 pm   #32
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Default Re: 80-BUS Loft treasure?

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Originally Posted by mole42uk View Post
Although I have decided to sell the hardware, I do still intend to use the floppy drives and try and recover as much of the 40+ floppies that I still have. Much of it seems to be software downloaded from an ancient BBS but there are several disks which are labelled as Gemini specific. I'll try and catalogue them over the next weeks.
Thanks, that would be great. I am particularly interested in archiving CP/M 2.2 versions particulalry Bios 1.4 on GEMQDSS (i.e. with the QDSS Disk Formatter), Bios 3.5 and Bios 3.2. Also I am missing all versions of Gempen.

I have the floppy only version of CP/M (Bios 3.5) but want to get hold of the Winchester version which I am pretty sure can be achieved with the addition of a couple of bios files called BIOSW and BIOSFW.
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