Kenda "The Professional" DMFS

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dsdf323
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Kenda "The Professional" DMFS

Post by dsdf323 » Mon Aug 10, 2020 10:53 pm

Greetings from Australia.

I acquired a bunch a BBC Model Bs about ten years ago - they're pretty rare here in Australia ... we look longingly at the number of Model Bs you can pick up "cheaply" in the UK ... as they don't have £100+ shipping ;)

I'm still quite new to them, having grown up with an Amstrad CPC464. I got my first one at uni. in the 90s when they were selling them off ... I paid $15! But couldn't do anything with it - no disks, etc.

So when a bunch came up on eBay ten years ago, I got a hold of a few. But, with dodgy power supplies, etc. they were put away for future tinkering. Now it's the future and I'm fixing them up.

This one has the Kenda "The Professional" disk interface which I understand is pretty rare & undocumented.

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Is there anything I can do to help document it?

Brett.

Link to my Dropbox with images
Brett.

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Re: Kenda "The Professional" DMFS

Post by dsdf323 » Tue Aug 11, 2020 1:34 am

Ah huh,

Okay I tried a search for "kenda dmfs pads" and finally found a brochure with some details.

Kenda Professional DMFS with PADS

Kenda Electronic Systems - DMFS with PADS.pdf
(573.36 KiB) Downloaded 13 times
Last edited by dsdf323 on Tue Aug 11, 2020 3:17 pm, edited 2 times in total.
Brett.

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Re: Kenda "The Professional" DMFS

Post by dsdf323 » Tue Aug 11, 2020 1:57 am

And from BEEBUG Vol 2, Issue 8 (Jan/Feb 1984) - uses an 8272?
Unfortunately, the 8271 disc controller used in the BBC micro is incapable of providing double density format, and so another controller must be used instead. This is usually the 8272 which can support both single and double density modes. Since this chip is not pin compatible with the 8271, it must be used with a special carrier board which will plug into the normal 8271 socket. Two systems that follow this course of action and provide true double density on the BBC micro are now available.
BEEBUG Vol.2 Issue 8
Brett.

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Re: Kenda "The Professional" DMFS

Post by Pernod » Tue Aug 11, 2020 2:20 am

dsdf323 wrote:
Mon Aug 10, 2020 10:53 pm
This one has the Kenda "The Professional" disk interface which I understand is pretty rare & undocumented.

Is there anything I can do to help document it?
This is a great find, and glad you're willing to help understand it =D>

We really need to know what's inside the box. There will be a floppy controller (8272?) to identify and a ROM (8K?) to dump, and an amount of RAM (2K?) to identify. Is it possible to open it without damage?

It's curious to see it has a 24 pin header in a ROM socket, which suggests it may not be possible to image the ROM in situ, it's likely banked in some way with some RAM.

Do you also have the manual and utilities with it? It doesn't look like there's a formatter in ROM so may be useless without the utilties disc, especially as it doesn't support the usual Acorn DFS format.
- Nigel

BBC Model B: ATPL Sidewise, Acorn Speech, 2xWatford Floppy Drives, AMX Mouse, Viglen case, BeebZIF, etc.

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Re: Kenda "The Professional" DMFS

Post by dsdf323 » Tue Aug 11, 2020 3:04 am

Thanks for the reply Nigel.

Unfortunately I've only got the hardware and it's one solid chunk of epoxy. I do have a bunch of 5.25" disks but none appear to be an original-labelled utilities disk, but maybe there is a backup on an unlabelled disk ... ??

I did try sticking the 24-pin plug from the EPROM socket into my EPROM reader but it couldn't read anything, although I did try it as a 2732 as it was only 24-pin and not 28-pin.

I'm going to pull out that mess of bodge wiring for the 27512 EPROMs.

Is there any software available as a ROM that I can use to try to poke around whilst it's in-situ? I've got RetroClinic Mark's DataCentre-E which I might be able to use to save anything I can recover (?)

Brett.
Brett.

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Re: Kenda "The Professional" DMFS

Post by dsdf323 » Tue Aug 11, 2020 3:20 am

BTW, when I originally powered it on the screen was all sorts of weirdness.

"Massaging" the Video ULA got a solid, but inverted, image.

Just noticed this morning that pin 27, INVERT bar, was deliberately un-socketed (if that's the correct word). Each to their own, I guess ;)

Image
Brett.

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Re: Kenda "The Professional" DMFS

Post by Kazzie » Tue Aug 11, 2020 7:46 am

Most of the time, if you were using a 24-pin EPROM in a 28-pin socket, you'd mount it at the base, to align the data and address pins etc.

That arrangement, with the transition socket mounted at the top, leaves three data pins and ground unconnected. The data bus is also accessible from the 8271 socket (and ground, or course), so this may be a case of using a cheaper 24-pin IDC transition socket to reduce manufacturing costs.

If you wanted to try dumping the EPROM, you could mount the IDC socket in the same manner within the 28-pin socket of your reader, and use four flying (breadboarding) leads from the base of the Kenda to the remaining pin locations.
BBC Model B 32K issue 7, Sidewise ROM board with 16K RAM
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Re: Kenda "The Professional" DMFS

Post by marcelaj1 » Tue Aug 11, 2020 8:42 am

Hi,
Just did a bit of digging and the company still seems to be in Southampton, it may be worth giving them a shout...

http://www.kenda.co.uk/index.html

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Re: Kenda "The Professional" DMFS

Post by dsdf323 » Tue Aug 11, 2020 8:50 am

Kazzie wrote:
Tue Aug 11, 2020 7:46 am
If you wanted to try dumping the EPROM, you could mount the IDC socket in the same manner within the 28-pin socket of your reader, and use four flying (breadboarding) leads from the base of the Kenda to the remaining pin locations.
Thanks, that makes sense.

Willing to try.

If I understand correctly, put the 24-pin plug into the EPROM reader as if it were 28-pin, then connect the missing pins 13/14/15/16 from the controller.

D2: pin 13 to 8271 pin 14
GND: pin 14 to 8271 pin 20
D3: pin 15 to 8271 pin 15
D4: pin 16 to 8271 pin 16
Last edited by dsdf323 on Tue Aug 11, 2020 8:55 am, edited 1 time in total.
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Re: Kenda "The Professional" DMFS

Post by dsdf323 » Tue Aug 11, 2020 8:54 am

marcelaj1 wrote:
Tue Aug 11, 2020 8:42 am
Hi,
Just did a bit of digging and the company still seems to be in Southampton, it may be worth giving them a shout...

http://www.kenda.co.uk/index.html
I did wonder. Will definitely try - expecting first response to be puzzlement ;)

I got an old 80386SX system that had been locally assembled by a company called Total Peripheral Group back in the 90s.

They are now a large ISP/Telco here in Australia ... TPG ... and have just merged with VF (who had merged with Hutchison some years back to become VHA).

I sent them an email saying "just wanted you to know that one of your machines is still running!" ... only to get a puzzled reply from an Indian support rep. asking what was the issue with my broadband.
Brett.

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Re: Kenda "The Professional" DMFS

Post by dsdf323 » Tue Aug 11, 2020 9:17 am

dsdf323 wrote:
Tue Aug 11, 2020 8:50 am
If I understand correctly, put the 24-pin plug into the EPROM reader as if it were 28-pin, then connect the missing pins 13/14/15/16 from the controller.

D2: pin 13 to 8271 pin 14
GND: pin 14 to 8271 pin 20
D3: pin 15 to 8271 pin 15
D4: pin 16 to 8271 pin 16
Unfortunately no luck connecting it up like this. It did "read" it but the buffer was empty.

Image
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Re: Kenda "The Professional" DMFS

Post by marcelaj1 » Tue Aug 11, 2020 10:44 am

Indian call centre you say....I get calls from them saying they are going to cut off my broadband unless I give them all my bank details [-X :^o

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Re: Kenda "The Professional" DMFS

Post by Prime » Tue Aug 11, 2020 11:03 am

Not very professional making a product that can't be repaired if it goes wrong......

One obsevation is I don't think you're gonna read anything through the 24 pin socket, it's not connected to 3 of the data lines, (D2, D3 and D4), so Data must be coming out through the 40 pin socket. More than likely the 24 pin socket is being used to pick up the address lines.
So my guess is that to read the ROM you'd need to use the address lines from the ROM socket and the data lines from the 40 pin socket.

Cheers.

Phill.

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Re: Kenda "The Professional" DMFS

Post by darren-s » Tue Aug 11, 2020 11:15 am

Interestingly the company are still going at the same location http://www.kenda.co.uk/ they don't list the interface on their current products though ;-)

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Re: Kenda "The Professional" DMFS

Post by Pernod » Tue Aug 11, 2020 12:48 pm

As you've already got EXMON 2 in there then may as well use it.

Start EXMON with *E, then P 8000 to see header of currently selected ROM:
0400.png
Type ! x (where x is bank 0-F) until you see the Kenda ROM being shown.

Now move the 16K block from ROM into RAM with M 8000->C000, 2000

You can now save this as an image onto your DataCentre for export with *SAVE KENDA 2000+4000

I also wouldn't mind a copy of Toolkit 1.26b as the latest I currently have is 1.25b.
- Nigel

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Re: Kenda "The Professional" DMFS

Post by dsdf323 » Tue Aug 11, 2020 1:20 pm

Thanks for the details Nigel, will have a crack tomorrow. Will burn a new copy of that EXMON 2 to a fresh EPROM and hook up the DataCentre.

I've dumped both 27512 EPROMs and have copied them to my Dropbox link in the original post - the EXMON binary is at the start of the IC88 dump.

I've stripped all the bodged stuff out and put in an original BASIC2 ... now the DMFS/PADS is not showing up at all, so maybe one or more bodge wires were needed ... hopefully I didn't clumsily mess it up in the EPROM reader.

I compared the support chips listed for the 8271 with what is installed - don't know if it's of any interest, but for the cause of full documentation:

IC79 - 74LS38 - present
IC80 - 74LS38 - present
IC81 - 74LS393 - absent
IC82 - 74LS10 - absent
IC83 - CD4013B - absent
IC84 - CD4013B - absent
IC85 - CD4020B - absent
IC86 - 74LS393 - absent, 74LS04 hex inverter instead with pin 2 joined to pin 3 socket
IC87 - 74LS123 - present

Image

Image
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Re: Kenda "The Professional" DMFS

Post by Pernod » Tue Aug 11, 2020 1:30 pm

dsdf323 wrote:
Tue Aug 11, 2020 1:20 pm
... now the DMFS/PADS is not showing up at all, so maybe one or more bodge wires were needed ... hopefully I didn't clumsily mess it up in the EPROM reader.
That would be very unfortunate, but possible [-o<
- Nigel

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Re: Kenda "The Professional" DMFS

Post by dsdf323 » Tue Aug 11, 2020 1:34 pm

Pernod wrote:
Tue Aug 11, 2020 1:30 pm
dsdf323 wrote:
Tue Aug 11, 2020 1:20 pm
... now the DMFS/PADS is not showing up at all, so maybe one or more bodge wires were needed ... hopefully I didn't clumsily mess it up in the EPROM reader.
That would be very unfortunate, but possible [-o<
False alarm! I reseated that IDC header into another socket and it's all come good.

It's about 22:30 now but will quickly burn a new copy of EXMON and see what that produces ...
Brett.

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Re: Kenda "The Professional" DMFS

Post by Pernod » Tue Aug 11, 2020 1:50 pm

dsdf323 wrote:
Tue Aug 11, 2020 1:20 pm
I've dumped both 27512 EPROMs and have copied them to my Dropbox link in the original post - the EXMON binary is at the start of the IC88 dump.
I took a look at the Toolkit 1.26b in there, it's actually 1.25b but hacked to run in the upper half of the 16K bank. So all absolute page references are increased by 2.
dsdf323 wrote:
Tue Aug 11, 2020 1:34 pm
False alarm! I reseated that IDC header into another socket and it's all come good.

It's about 22:30 now but will quickly burn a new copy of EXMON and see what that produces ...

=D>
Last edited by Pernod on Tue Aug 11, 2020 3:11 pm, edited 1 time in total.
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Re: Kenda "The Professional" DMFS

Post by dsdf323 » Tue Aug 11, 2020 2:02 pm

All sorts of shenanigans.

I can see that the ROM sockets have been replaced so I'm wondering what other bodgery has been done.

The Kenda now only seems to work in IC100 position - it was originally in IC88.

Trying the Kenda back in IC88 and EXMON and RamFS in IC100 and IC52 shows nothing but BASIC - no RamFS, EXMON or Kenda.

So I removed BASIC from IC101 and put EXMON in there - straight into the EXMON screen.

I wondering if maybe I need to transplant to another BBC.
Brett.

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Re: Kenda "The Professional" DMFS

Post by dsdf323 » Tue Aug 11, 2020 2:15 pm

Success ... almost?

Does this look promising?

Will try to get RamFS working in there as well tomorrow so I can copy to the DataCentre.

Looking at the sockets - pin 1 of IC88 looks missing or pushed-in, but this is just Vpp for programming so shouldn't affect normal functionality ... ? And you can see IC101 has been changed for a fancy turned-pin one.

Image

Image
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Re: Kenda "The Professional" DMFS

Post by Pernod » Tue Aug 11, 2020 2:18 pm

dsdf323 wrote:
Tue Aug 11, 2020 2:02 pm
Trying the Kenda back in IC88 and EXMON and RamFS in IC100 and IC52 shows nothing but BASIC - no RamFS, EXMON or Kenda.
Sounds like bad contacts, keep trying.
dsdf323 wrote:
Tue Aug 11, 2020 2:02 pm
So I removed BASIC from IC101 and put EXMON in there - straight into the EXMON screen.
It's booting into EXMON as it's now the highest priority language.
dsdf323 wrote:
Tue Aug 11, 2020 2:15 pm
Success ... almost?

Does this look promising?
Looks great!
- Nigel

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Re: Kenda "The Professional" DMFS

Post by dsdf323 » Tue Aug 11, 2020 3:10 pm

Done!

I realised that there was a link from S20 to the bodged 27512 EPROMs that I'd removed (as it was soldered to the damn things) ... so I put a link back to NORTH and it could now see those sockets again! So I had RamFS, EXMON, and PADS.

So I've dumped, I think, the ROM and copied it to my Dropbox.

Code: Select all

***************** KENDA  GROUP ** Ken Fletcher *****************
Wow, how easy is it to use Mark's DataCentre and the USB!

KENDA_PADS_102.ROM
Kenda DMFS PADS v1.02 ROM
(16 KiB) Downloaded 10 times
Last edited by dsdf323 on Tue Aug 11, 2020 3:16 pm, edited 2 times in total.
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Re: Kenda "The Professional" DMFS

Post by dsdf323 » Tue Aug 11, 2020 3:13 pm

Indeed! =D>
********** Thanks are due to the following contributors - Ken Fletcher, Ken Fletcher, NEGFB, and Ken Fletcher **********
Last edited by dsdf323 on Tue Aug 11, 2020 3:32 pm, edited 1 time in total.
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Re: Kenda "The Professional" DMFS

Post by Pernod » Tue Aug 11, 2020 3:20 pm

Excellent, it looks like we have a good dump =D>

A quick analysis says it's an 8K ROM which is mirrored, and has 2K RAM at offset &3000-37FF, which is also mirrored upto &3FFF.

The only evidence of it using a 8272 is the Beebug review, so lets hope that's true.

Also, from the Kenda flyer there's a *CURE command which sounds like it should read standard Acorn DFS, so this should give me an emulation test case to play with as we don't have the utilities floppy.
- Nigel

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Re: Kenda "The Professional" DMFS

Post by dsdf323 » Tue Aug 11, 2020 3:22 pm

It's from 2005 ... but there was an email address at Kenda for him!

http://www.kenda.co.uk/pr/autodata_ke204a.html

{Edit: did try it, unsurprisingly it bounced ... the ROM is from 1985, the press release from 20 years later in 2005, and it's now 15 years after that ... hoping he's still around and simply happily retired}
Last edited by dsdf323 on Tue Aug 11, 2020 3:39 pm, edited 1 time in total.
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Re: Kenda "The Professional" DMFS

Post by dsdf323 » Tue Aug 11, 2020 3:28 pm

Pernod wrote:
Tue Aug 11, 2020 3:20 pm
The only evidence of it using a 8272 is the Beebug review, so lets hope that's true.
I was reading "Disk Systems For The BBC Micro" by Ian Sinclair to try to get more background and it mentioned on p8 about single & double density:
"Many computers allow 'double density' recording, which means that each sector has twice as much information (512 bytes) placed on it. This cannot be done with the BBC system, no matter which of the DFS chips is used, because the 8271 chip which controls the disk operation simply does not permit operation at double density. At the time of writing, as least two firms were offering add-on disk-operating boards which featured a different controller. These would support double-density operation ..."
Unfortunately it doesn't actually name the companies or the actual controller but it could be a good bet that maybe they are the ones referenced in the BEEBUG article? Just thought it was interesting - had I read this a week ago, before I starting poking around with it, it wouldn't have registered at all ...
Brett.

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Re: Kenda "The Professional" DMFS

Post by Pernod » Tue Aug 11, 2020 4:53 pm

dsdf323 wrote:
Tue Aug 11, 2020 3:28 pm
Unfortunately it doesn't actually name the companies or the actual controller but it could be a good bet that maybe they are the ones referenced in the BEEBUG article?
I already emulate almost all known BBC floppy controllers, listed over at viewtopic.php?f=4&t=11633. The 8272 wasn't commonly used, only found on the early Opus and Microware boards. Most other suppliers opted for a more common Western Digital controller.
- Nigel

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Re: Kenda "The Professional" DMFS

Post by Pernod » Wed Aug 12, 2020 12:48 pm

After some initial investigation I can now conclusively say that it does not use a 8272!

It's performing R/W to addresses &FE80-83 and &FE84 looks like a write only drive control register. The data being written to &FE80 looks very Western Digital compatible, the first write is &D0 (Force Interrupt) which Kenda is using in it's diagnostics to confirm the FDC is present. See bottom of Kenda flyer for Auto diagnostic errors for FDC,RAM,ROM. These all pass!

If I compare *. with *.1 the commands issued are the same except the data written to &FE84 changes from 0 to 1, which suggests bit 0 is the drive select bit.

Western Digital produced a range of FDC's, many of which were used in controller boards from various suppliers, so which one did Kenda use? Possible candidates are: (there are others but have limited the list to what are known to be used on other boards)
FD1797 (Computer Village)
WD2791 (Opus)
WD2793 (Opus, UDM)
WD2797 (Cumana)
WD1770 (Watford, Opus, Acorn, Solidisk)

My first attempt is using the FD1797. I can see the DFS catalogue being loaded into the 2K RAM, but it returns a CRC error. As it gets this far then I've removed the WD2791 as a candidate as that uses an inverted bus and wouldn't get this far.

The Kenda 1.02 ROM is dated 1985, but was reviewed in Beebug early 1984 which suggests an earlier ROM will be out there which may or may not use the same FDC. (I know UDM switched from 8272 in their 0.9x ROM to using a WD2793 with their 2.00 ROM)

I'm also thinking 1984/85 is a little early for general WD1770 use, wasn't widely adopted until Acorn went with it in 1985.

Anyone have any suggestions as to how the FDC could maybe be probed to help determine the type used?

So next attempt will be with the WD2793, to be continued ...
- Nigel

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Re: Kenda "The Professional" DMFS

Post by dsdf323 » Wed Aug 12, 2020 2:17 pm

Wow, excellent Nigel - really enjoying this.

Is there anything I can do on the hardware? Is there any software or commands I can run that can interrogate registers, etc. on the FDC that could hint at which one it is?
Brett.

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