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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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21st May 2021, 6:25 am | #21 | |
Octode
Join Date: May 2018
Location: Northampton, Northamptonshire, UK.
Posts: 1,394
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Re: 80-BUS Loft treasure?
Quote:
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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21st May 2021, 4:43 pm | #22 |
Dekatron
Join Date: May 2008
Location: Derby, UK.
Posts: 7,735
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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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21st May 2021, 5:03 pm | #23 | |
Dekatron
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,484
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Re: 80-BUS Loft treasure?
Quote:
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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21st May 2021, 8:11 pm | #24 |
Dekatron
Join Date: May 2008
Location: Derby, UK.
Posts: 7,735
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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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If I have seen further than others, it is because I was standing on a pile of failed experiments. |
21st May 2021, 8:15 pm | #25 |
Nonode
Join Date: Aug 2010
Location: Resolfen, Wales; and Bristol, England
Posts: 2,588
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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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23rd May 2021, 7:16 am | #26 | |
Octode
Join Date: May 2018
Location: Northampton, Northamptonshire, UK.
Posts: 1,394
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Re: 80-BUS Loft treasure?
Quote:
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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23rd May 2021, 2:12 pm | #27 |
Hexode
Join Date: Jan 2016
Location: Ramsgate, Kent, UK.
Posts: 296
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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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Andrew Illegitimi non carborundum Last edited by MeerKat; 23rd May 2021 at 2:24 pm. Reason: More detail |
31st May 2021, 12:55 pm | #28 |
Nonode
Join Date: Aug 2010
Location: Resolfen, Wales; and Bristol, England
Posts: 2,588
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Re: 80-BUS Loft treasure?
Here are some photos:
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Richard Index: recursive loop: see recursive loop |
31st May 2021, 12:56 pm | #29 |
Nonode
Join Date: Aug 2010
Location: Resolfen, Wales; and Bristol, England
Posts: 2,588
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Re: 80-BUS Loft treasure?
And a few more:
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Richard Index: recursive loop: see recursive loop |
24th Jun 2021, 8:07 pm | #30 | |
Hexode
Join Date: Apr 2019
Location: Skipton, North Yorkshire, UK.
Posts: 252
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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.
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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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24th Jun 2021, 10:18 pm | #31 |
Nonode
Join Date: Aug 2010
Location: Resolfen, Wales; and Bristol, England
Posts: 2,588
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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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Richard Index: recursive loop: see recursive loop |
24th Jun 2021, 11:05 pm | #32 | |
Hexode
Join Date: Apr 2019
Location: Skipton, North Yorkshire, UK.
Posts: 252
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Re: 80-BUS Loft treasure?
Quote:
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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