A680s

Arc/RPCs, peripherals, RISCOS operating system & ARM kit eg GP2x, BeagleBoard
philb
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A680s

Postby philb » Fri Aug 25, 2017 2:08 pm

In the process of tidying up my study I have come across a stack of five and a half (!) A680 motherboards. I think all of them have at least something wrong with them, but it looks at a first glance as though there are probably enough good parts in there to make at least one working unit. Anybody interested in a project?

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z0m8ied0g
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Re: A680s

Postby z0m8ied0g » Fri Aug 25, 2017 3:09 pm

I'm interested in them, let me know what you want for them.
Acorn... lots of Acorn... http://blog.retroacorn.net

steve3000
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Re: A680s

Postby steve3000 » Fri Aug 25, 2017 7:23 pm

Also interested, particulary if you think it's likely the faults or damage are repairable.

I'd hope between the forum the would be enough parts to resurrect more than one of these rarities and if successful possibly one (or more) could end up in a retro computer museum...

philb
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Re: A680s

Postby philb » Fri Aug 25, 2017 7:47 pm

Righto, I'll see if I can find a few minutes to get them all out and catalogue what state each of the boards seems to be in. I think most of them probably are repairable given enough parts and determination.

RobC
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Re: A680s

Postby RobC » Fri Aug 25, 2017 9:12 pm

I'd also be interested (assuming they aren't already spoken for). I have restored an R260 and an A540 in the past...

philb
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Re: A680s

Postby philb » Sat Aug 26, 2017 6:32 pm

I took some photos of the boards I have.

https://goo.gl/photos/38RztCBTqBBCXQ8r6

It turns out on closer inspection that one of them is a "one-and-a-half" configuration. I think this was a prototype for the 16MB configuration used in the A540. This is the one that also has an Econet module grafted onto the edge of it. I think the half-board is the other part of the one that got sawn in two to make this prototype.

The other ones need some further analysis to work out which ICs are missing and which ones need/ought to be there. Most of the boards seem to be missing VIDC in particular; I don't know how easy it is to obtain those parts.

RobC
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Re: A680s

Postby RobC » Sat Aug 26, 2017 7:52 pm

philb wrote:I took some photos of the boards I have.

https://goo.gl/photos/38RztCBTqBBCXQ8r6

It turns out on closer inspection that one of them is a "one-and-a-half" configuration. I think this was a prototype for the 16MB configuration used in the A540. This is the one that also has an Econet module grafted onto the edge of it. I think the half-board is the other part of the one that got sawn in two to make this prototype.

The other ones need some further analysis to work out which ICs are missing and which ones need/ought to be there. Most of the boards seem to be missing VIDC in particular; I don't know how easy it is to obtain those parts.

Thanks - they look really interesting. Do you know their history?

I think I have at least one spare VIDC somewhere (probably some MEMCs and IOCs too) but, in any case, CJE still stock them:
http://www.cjemicros.co.uk/micros/individual/newprodpages/prodinfo.php?prodcode=VLSI-ARM-VIDC

steve3000
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Re: A680s

Postby steve3000 » Sat Aug 26, 2017 8:19 pm

Really interesting to see these photos. The boards are clearly in varying states of configuration, as you say, it looks like at least one might be in a state which could function.

To get the others working may/may not be possible, but would certainly need some time and effort to compare with the most complete board - and certainly a selection of spare parts, but most difficult might just be getting a bootable operating system. The RISC OS 2 era ROMs present on some of the PCBs say "boot rom" - which presumably indicate they provide the basic boot code, expecting to load RISC iX from a SCSI HDD? Do you have any HDDs from these?

I guess first steps would be to dump the ROMs from all, and compare. Depending on how official the ROMs are, it may be possible to boot them under emulation to test further, especially as Arculator has been tweaked to load RISC iX.

Next steps identify the missing components from all PCBs and document the differences.

There are lots of useful details, including various technical drawings, available on Chris' Acorns, which might just be enough to get these running: http://chrisacorns.computinghistory.org ... uters.html

:)

steve3000
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Re: A680s

Postby steve3000 » Sat Aug 26, 2017 8:26 pm

RobC wrote:I think I have at least one spare VIDC somewhere (probably some MEMCs and IOCs too) but, in any case, CJE still stock them:
http://www.cjemicros.co.uk/micros/individual/newprodpages/prodinfo.php?prodcode=VLSI-ARM-VIDC

Would be great if between the community we could restore some of these, I'd be more than happy to donate from my spares box - and if we could resurrect one for a future French "ZAP" museum, I'm sure we'd have another eager contributor. ;)

RobC
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Re: A680s

Postby RobC » Sat Aug 26, 2017 8:27 pm

steve3000 wrote:The RISC OS 2 era ROMs present on some of the PCBs say "boot rom" - which presumably indicate they provide the basic boot code, expecting to load RISC iX from a SCSI HDD? Do you have any HDDs from these?

I've seen various references that suggest the A680 didn't have a RISC OS component (like the R140 or R260). So, I guess the ROMs hold a boot loader to get RISC iX started from the SCSI HDD.

If they could be dumped, I could try the A680 ROM images in my R260. I've also got a clone of my R260 HDD on a standalone SCSI drive (RISC iX v1.21c). Not sure whether the A680 had its own version of RISC iX though?

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daveejhitchins
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Re: A680s

Postby daveejhitchins » Sun Aug 27, 2017 6:51 am

I'm asking, on behalf of Xavier's Museum collection (Zarchos), if there is one free, even if most/all of the parts have been removed, it could be saved for him.

Thanks - Dave H :D
Parts: UM6502CE, GAL22V10D, GAL16V8D, AS6C62256A, TC514400AZ, WD1772, R6522, TMS27C512, AT28C256
Products: ARA II, ABR, ATI, AP6, MGC, AP5 . . .
For a price list, contact me at: Retro Hardware AT dave ej hitchins DOT plus DOT com

Boydie
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Re: A680s

Postby Boydie » Sat Sep 02, 2017 9:09 am

It's a bit late, but I may be interested in one too.

As regards the OS side of things, these are my recollections of trying to get mine working a couple of years back...

The ROMs on board aren't RISCOS, but a basic boot kernel. ISTR this gives a *very* rudimentary shell with about a dozen or so commands, including those for setting the CMOS with where to boot from etc. Not too sure why this took four ROMs to achieve - there doesn't seem to be an awful lot of functionality. Never tried installing RISCOS, but I suspect it may barf somewhat at the different hardware (esp on-board scsi), and !RISCiX almost certainly wouldn't cope. This boot kernel isn't documented in the manuals or TRMs. You have to peice things together from a slim built-in help system.
The A680 seems to be quite happy to accept scsi drives other than the Rodime it came with, which is probably just as well as they usually died decades ago. Bear in mind that only drives less than 2GB will work - RISCiX's bizarre filing system structure means than anything larger will actually be perceived as having negative capacity!
Booting is slightly more complicated than with other RISCiX machines. On other machines, !RISCiX makes it boot from the first RISCiX partition available, the location of which I presume gets stored somewhere in the partition table and can be found by ADFS for !RISCiX). The A680 kernel needs to be told where the parition is on the disc, so it's vitally important to keep a record of where the partitions are when you format the drive.
Drive nomenclature is different on the A680 - it refers to the on-board scsi drives as "sc<x>" rather than the "sd<x>" used for the scsi podules on other machines (I presume "sd<x>" will work if you're using a scsi podule as well). So you'll have to define a whole set of "sc" devices for riscix. I don't know how to do this, but I know someone who does.
The A680 has its own variant of vmunix (again presumably to cope with the novel hardware). I allegedly have a copy, supplied by Dave Walker at Acorn, but have never quite succeeded in getting it to boot, either from floppy or when copied over to the HD. It always complains about not being executable (as indeed does a copy of standard vmunix). Setting file permissions doesn't seem to help. If anyone has any suggestions, I'd be glad to hear them.
Video on the A680 is a bit of a pig, having only BNC hi-res connectors. I eventually managed to hook it up to a 21" Iiyama using a BNC->sVGA lead.

There are a few A680s knocking around which seem to boot fully into RISCiX. Chris Whitehead's machine which he donated to TNMoC has screenshots. It may be an idea to archive one of these before their drives die.

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IanS
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Re: A680s

Postby IanS » Sat Sep 02, 2017 10:28 am

Boydie wrote:Not too sure why this took four ROMs to achieve - there doesn't seem to be an awful lot of functionality.

They data needs to be 32-bits wide to be executable at power-on.

Boydie
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Re: A680s

Postby Boydie » Tue Sep 05, 2017 6:40 am

If somebody can recommend a disc imaging program that will cope with alien formats, preferably for the RiscPC but an older Arc will do at a pinch (not got a PC with floppy drive in the house these days), I'll upload an image of my A680 vmunix floppy.

I suspect I'm just not unix-savvy enough to restore RISCiX on an A680 myself, but if it helps get more of the beasts working...

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davidb
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Re: A680s

Postby davidb » Tue Sep 05, 2017 11:02 am

I found DImager in another thread, though I've not tried it. Back when I used my A7000+, I occasionally used ADFimager to read ADFS format floppies, but that might not be appropriate for this task.

No doubt experts like sirbod and steve3000 can recommend something to do low-level reads from the disk if the tools mentioned above don't work. :)

ajw99uk
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Re: A680s

Postby ajw99uk » Sun Oct 08, 2017 10:13 pm

Boydie wrote:If somebody can recommend a disc imaging program that will cope with alien formats, preferably for the RiscPC but an older Arc will do at a pinch (not got a PC with floppy drive in the house these days), I'll upload an image of my A680 vmunix floppy.

I suspect I'm just not unix-savvy enough to restore RISCiX on an A680 myself, but if it helps get more of the beasts working...

Maybe easier to pull the kernel straight off the hard disc if you can mount its root partition on an Arc with RISC iX or maybe just RISCiXFS. I don't think there's anything magic about the kernel disc beyond its 4.3 filesystem, and one could probably adapt the mkkernel script to create a new one using the A680 kernel.
Come to think of it, how does this look:

Boot an Arc into 1.21c single user
mkdir /a680
Insert A680 kernel floppy
dd if=/dev/fdf1024 of=/a680/kernel_disc

This will yield an 800K file (assuming same filesystem as RISC iX 1.15) which can then be ftp'd elsewhere (for Ether1, the RISC iX driver seems about 50% faster than RISC OS, but still well below 10Mbit).
Last edited by ajw99uk on Mon Oct 09, 2017 2:45 pm, edited 1 time in total.
Running RISCOS: A5000, A540, R140, RiscPC, RPi B
Running *nix: SGI Fuel & Indigo2, RPi2, x86, amd64, RiscPC, A540, R140

sirbod
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Re: A680s

Postby sirbod » Mon Oct 09, 2017 5:22 am

davidb wrote:No doubt experts like sirbod and steve3000 can recommend something to do low-level reads from the disk if the tools mentioned above don't work. :)
For raw sector data DiscOp 1? Define the disc record, then call the filesystem it's attached too, eg ADFS_DiscOp

SYS "<file system>_DiscOp",, 1 + (<disc record address> >> 6), <disc address>, <memory address>, <size>


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