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Old 29th Dec 2017, 5:05 am   #1
arjoll
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Default BBC Master boot

Inspired by the thread about running a BBC into a modern monitor, I have decided to try to get the Master 128 Paul sent over running.

I have got it working through a GBS8200 to an old HP L1502 LCD monitor. I have a number of these that I picked up from a client who was going to put them into ewaste - the same client that I picked up a number of vintage computers from, including a CBM8032, HP 85, Amstrad 6128 and Apple IIe.

Anyway, the GBS8200 is doing the job fine so far - it's showing me that the Master is reporting two messages but doesn't appear to be dropping in to BASIC. I am getting:
Code:
Acorn MOS
Acorn ADFS
The machine came with a couple of ROM cartridges with two EPROMs in each, but all but one of the EPROMs had their windows uncovered so I'm not sure what is on them. Plugged in they either give me the same message or just Acorn MOS depending on the order.

Going out on a limb, and without much in-depth understanding of BBCs, does this mean that I only have the ADFS ROM and not the BASIC ROM? If that's the case, what ROMs should I keep an eye out for?

I've attached a closeup of the message (contrast bumped up a bit in Photoshop, the camera was struggling with the amount of light around on another nice summer's day!), the setup (and messy workshop) and a closeup of the GBS8200. I originally purchased it to run with the Sords, so made up a cable from the converter to a DA15, then DA15 to whatever end the computer needs so I can swap over easily - DA15 seems an odd choice, but I had a heap left over from another project that never really happened....
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Old 29th Dec 2017, 5:36 am   #2
TonyDuell
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Default Re: BBC Master boot

As it's a Master, most likely the contents of the CMOS RAM are corrupted and it is not looking for the BASIC ROM but looking for a language ROM in some other position.

I seem to remember that you hold down a key at power-on and it will go into the default configuration, including BASIC. But I can't remember what the key(s) is -- ctrl-D perhaps?
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Old 29th Dec 2017, 5:57 am   #3
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Default Re: BBC Master boot

Thanks Tony - I've done a little more research, and have found that apparently Ctrl-F was supposed to work to drop me to something more useful - it doesn't, but holding down F while booting seems to do it.

This has raised another issue - I've got a number of keyboard faults, including useful keys like X, C and B. It's quite possible Ctrl is also an issue, although when testing a few of the ones that weren't showing on-screen with a multimeter (after removing the keyboard) I forgot to check that one. Unfortuantely squirting in CRC CO makes no difference, and I can't see how to disassemble the switches.

It looks like I'll need to buy a few keyswitches!
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Old 29th Dec 2017, 6:03 am   #4
TonyDuell
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Default Re: BBC Master boot

I seem to remember the Master has a numeric keypad. On other machines with such a feature (which is not essential) I have taken good switches from there to get the main part of the keyboard working properly and put the dud keyswitches in the numeric keypad area until I could get replacements.
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Old 29th Dec 2017, 6:10 am   #5
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Default Re: BBC Master boot

Excellent idea! I'll do that in the meantime
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Old 29th Dec 2017, 8:22 am   #6
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Default Re: BBC Master boot

Your Master is starting up with ADFS (the Advanced Disc Filing System) as the filing system. The first thing ADFS does is try to mount the disc. With no disc drive present, it will just sit there waiting. I recommend holding down the 'D' key while switching on, or while pressing the BREAK key. That should force the DFS (Disc Filing System) to be selected, which is much simpler and doesn't try to access the disc until you tell it to. That should get you to a BASIC prompt.

Now you can configure the machine because the CMOS RAM probably has junk in it. Type *ROMS to list the ROMs available. Identify which one is 'DFS', then do *CONFIGURE FS with that number. You can shorten *CONFIGURE to *CONF. (note the dot). That should save the preferred filing system in the CMOS RAM.

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Old 29th Dec 2017, 12:37 pm   #7
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Default Re: BBC Master boot

Thanks Chris. I will swap keyswitches around first - very hard to type configure without a C - and then see how I get on. I completely forgot to grab a battery holder from Jaycar when I got the cable, so will do that next time in town so the configuration data can be saved.
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Old 29th Dec 2017, 12:49 pm   #8
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Default Re: BBC Master boot

Glad to hear you're making progress of sorts with this. The keyswitches are probably just oxidised as this machine had been unused in my unheated loft for about ten years, and may have also been out of use for at least a decade before that. If you can dismantle them somehow you can probably repair them. I salvaged it for a data conversion job that never materialised.
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Old 29th Dec 2017, 2:28 pm   #9
cmjones01
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Default Re: BBC Master boot

I've just tried my own advice (always a good idea) on BeebEm set to Master 128 mode. It turns out that the command you want is *CONFIGURE FILE, not *CONFIGURE FS. I mis-remembered.

I also note that *ROMS lists ROM numbers in hexadecimal, but *CONFIGURE wants them in decimal, unless you prefix them with an ampersand (&).

Looking at your screenshot, you might also want to do *CONFIGURE MODE 7 to make it all easier to read!

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Old 29th Dec 2017, 2:31 pm   #10
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Default Re: BBC Master boot

A further note: try holding down the SHIFT key while you switch the machine on. It's possible that it's configured to try booting from a disc by default, which it won't be able to. In which case *CONFIGURE NOBOOT will fix it.

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Old 29th Dec 2017, 2:56 pm   #11
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Default Re: BBC Master boot

To clarify, when I acquired this machine it came with two floppy drives and some ribbon cable. Andrew decided that he didn't want them sent because of the cost (they are very heavy) and there was no guarantee that they would be serviceable.

I do still have the drives, but they haven't become any lighter. I don't have any floppies.
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Old 29th Dec 2017, 4:05 pm   #12
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Default Re: BBC Master boot

cjemicros.co.uk sell keyswitches for these if they won't clean up. Now I am retired I have recently setup my BBC system after it had laid dormant since the ninety's, one of my switches wouldn't respond to a spray so stripped it down and reassembled it and it works fine now. Arjoll there's loads of stuff out there about BEEBs just google it.

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Old 29th Dec 2017, 4:07 pm   #13
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Default Re: BBC Master boot

The Master keyswitches always were less reliable than the types used in the previous machines. Luckily for me, a service engineer left an assortment of key switches and other BBC parts in a cupboard at school, and after several failed attempts to reunite the engineer with his parts, the school gave up and let me have them. And this was in 1990, when the machines were relatively young. I don't remember any instances of non-Master keyswitches failing, but I've used up most of the Master ones now. The last Masters used a membrane keyboard, like modern PC keyboards, and these felt rather different, but in a good way.

Once the backup battery has been replaced, hold down R at power-up. This resets the CMOS RAM to a sensible state, and should give you access to a command line where you can type star commands like *ST., *ROMS, *CO., etc. The configuration options are covered in appendix C of the welcome guide - here if you haven't already found it: http://8bs.com/othrdnld/manuals/essentialsmaster.shtml (scroll to the bottom)

This is a good excuse to plug this site - https://bbc.godbolt.org/?model=Master# - a BBC emulator written in JavaScript (pretty amazing, really). You can type *ST. there to see a list of sensible defaults...
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Old 29th Dec 2017, 4:25 pm   #14
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Default Re: BBC Master boot

Further to the above, I've just tried holding down R while using the drop-down menu in the above JavaScript emulator to generate a hard reset, and it works as expected, coming back with a disc error after a couple of seconds (where your machine hangs because you don't have a disc drive). As suggested above, holding down D while hitting break will set the file system to DFS, so it won't be trying to read the disc catalogue at reset (that also works in the emulator).

That emulator is linked to the BBC Micro disc image archive, so you can spend hours playing around with all the old software. But of course, the next step is to make a serial lead and transfer these images to a real machine. With a floppy disc drive attached (you'll need a double-density type), you can then make discs from those images. It's pretty straightforward once you've got going: http://www.8bs.com/filecon.htm#Xfer

Oh, another guide to the CMOS RAM problem: http://8bs.com/artcmos.htm

Finally, I have a real Master setup upstairs, so can double-check things for you quickly if needed...

Enjoy
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Old 29th Dec 2017, 6:58 pm   #15
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Default Re: BBC Master boot

Quote:
Originally Posted by mhennessy View Post
Finally, I have a real Master setup upstairs, so can double-check things for you quickly if needed...
Glad I'm not the only one!

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Old 29th Dec 2017, 9:52 pm   #16
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Default Re: BBC Master boot

A worthwhile upgrade for your Master is MOS 3.50, You can check what's in yours with *FX0. I'm pretty sure I have the final version Acorn did, I am able to run a hard drive (Winchester) with mine. There are lots of useful additions, R Break (discussed above) puts a set of sensible values in the battery backed CMOS RAM. One way of telling if you may have the later version is do a *h. , the 'Advanced DFS' reports itself as '2.04' , earlier version of MOS 3.50 report '2.03'. Oh and though not guaranteed to be compatible with all software it runs Elite OK....Phew!!

Andrew
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Old 30th Dec 2017, 3:45 am   #17
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Default Re: BBC Master boot

Thanks everyone for the advice on this - I should have known that there would be a ton of information on BBCs out there!

Quote:
Originally Posted by paulsherwin View Post
The keyswitches are probably just oxidised as this machine had been unused in my unheated loft for about ten years, and may have also been out of use for at least a decade before that. If you can dismantle them somehow you can probably repair them.
I've tested and removed all the non-working keyswitches now - a total of 10 in the main keyboard, and another two in the numeric keypad. I've attached an image from just before I tested the keypad - I figured I may as well remove all the keycaps (except space, I hate reassembling space bars...) and clean it up.

Next step is to pull the keypad ones and use them on the main keyboard to get things running. Without useful keys like C and B, I had no way of getting the commands suggested here into the machine!

Quote:
Originally Posted by paulsherwin View Post
Andrew decided that he didn't want them sent because of the cost (they are very heavy) and there was no guarantee that they would be serviceable.
My main reason here was that I had no floppies to read, so the plan was to get the machine operational - using tape images if necessary - and then sort out some kind of SD reader for it. The only computers on my wishlist that I had media for were the Sord M23, M68 and Apple IIe (and PCs of course) - the BBC was on there simply because mum used one at the school she taught maths at and brought one home during holidays. At school we used Apple IIes until they replaced them with clone 8088 PCs in my sixth form year (1988), and at home we had Sords until dad bought a PC - also in my sixth form year!

Quote:
Originally Posted by Andrew64 View Post
cjemicros.co.uk sell keyswitches for these if they won't clean up.
I had a quick look - they aren't cheap so I might see how things go! They appear to be clipped together, but I didn't want to force them open in case they were glued as well, but I have nothing to lose by trying disassembly and a squirt of CRC CO then 2.26.

I've found a seller on eBay who has them for GBP2 plus postage - so maybe later in the year once the credit card has recovered from Christmas and getting the kids settled back in university.
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Old 30th Dec 2017, 4:41 am   #18
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Default Re: BBC Master boot

Another quick update. I figured I had nothing left to lose with the keyswitches, so carefully tried opening one up - they definately appear to be glued or fused together - photo 1 shows what happens with 30 year old plastic when you try to undo what appears to be a clip which turns out to be stuck to the black plastic it is "clipped" to!

At this point I really did have nothing left to lose, so referred to some information I found yesterday here about a Memotech keyboard which uses the same Futaba keyswitches. It detailed how the pins screw out (around two turns anticlockwise), so I tried that, squirted some CRC CO into each hole, worked the mech and then reinserted the legs.

Turns out that it works!

I now have 11 keyswitches that give a nice clean contact, and one that's a little scratchy, which will go back into the keypad.

I am not sure how long this fix will last, but in the meantime it has saved me spending GBP30.50 including shipping on 12 NOS keyswitches - and also is a technique I'll remember if any others start failing.

Photos - switch with broken clip, switch with one pin removed, switch after a couple of squirts of CO (in a small pool of CO, it evaporates pretty quickly), and the magic spray itself - works brilliantly on the switches in Akai tape recorders too
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Old 31st Dec 2017, 12:24 am   #19
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Default Re: BBC Master boot

I've had only one bbc master keyswitch die, they nearly always respond to repeated hammering after a dose of servisol. I think they suffer from tarnishing which quickly rubs away.
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Old 31st Dec 2017, 3:41 am   #20
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Default Re: BBC Master boot

Latest update. I've grabbed a small 4x AAA holder from Jaycar (they don't do 3xAA and this seemed the best option) and now have a configuration that stays. I've got it defaulting to booting into BASIC and what appear to be some sensible defaults set.

Next quesion - the machine came with two ROM cartridges. Both had two EPROMS - one a 27128 labelled "RAMROD" and an unlabelled 27256, the other two unlabelled 27256s. All except "RAMROD" had nothing covering the window.

I have now stuck some some silver floppy disk write protect labels over the windows. I'm not sure how quickly EPROMs can be erased with nothing over the windows, but they only came out of the bag they were sent in for a few seconds at a time, and never outside in Southland's high UV environment.

With these inserted, I either get garbage on boot, or three additional ROMs showing up:
  • ROM 3 MASTER ROM 01
  • ROM 2 MASTER-ROM 01
  • ROM 0 RAMROD 01

ROM 1 (presumably the 27256 in the same cartridge as RAMROD) is showing ?. With the cartridges installed, I notice the Master locks up quite frequently, but BREAK will reset it.

Should I assume the content of these EPROMs has been scrambled by the blank windows and/or old age, or if not is there some way to find out what they are? Do the names seem familiar?

I am getting a good display and colour through the GBS8200 - the only complaint is that I have to reset the geometry when changing modes, although haven't identified that if it is just mode 7 that is different or if all of them have other differences. The picture is nice and clear, no shimmering, and it's only using around 450 mA through my bench supply so the reports of the converter needing a 2A supply seem to be false (although I have a spare 5V 2A supply I'll be using on it anyway).

Caps Lock doesn't appear to work, but it was one of my repaired keyswitches so I suspect the repair didn't "take." I'll swap it with something on the keypad or maybe Shift Lock. Getting used to the UK keyboard will be interesting, I'm used to " being shift-2 and * being shift-8, and have no use for a pound key!

Other than that, I believe I have a working Master. Thanks to everyone for their help, especially Paul Sherwin for fishing it out and sending it over!
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