A5000 with Risc Developments Dual MEMC2

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DutchAcorn
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A5000 with Risc Developments Dual MEMC2

Post by DutchAcorn » Sun Aug 23, 2020 8:41 pm

This ebay auction intrigued me. It was first offered BIN £250 but later re-listed for bidding.

It is sold as not working and from the seller I heard that the drive LED was blinking. The pictures that were added later show a "Dual MEMC" expansion from Risc Developments. So this is likely an 8 MB memory expansion. There could be battery damage, but it does not look too bad from the pictures.
dual memc2.jpg
I "won" the auction but am awaiting p&p which may be "interesting" to The Netherlands because it is over 10 KG. I would not mind to sell it on (and have it sent) to a UK based Stardot member on the condition that progress on this machine is reported back here and any interesting software archived. Please PM me if interested.

Note: depending on the P&P I may still decide to have it sent across the pond..
Paul

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SarahWalker
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Re: A5000 with Risc Developments Dual MEMC2

Post by SarahWalker » Sun Aug 23, 2020 9:10 pm

I'd be interested in this.

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Re: A5000 with Risc Developments Dual MEMC2

Post by steve3000 » Sun Aug 23, 2020 9:37 pm

Good win! It's also a 33MHz ARM3 A5000a. :)

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Re: A5000 with Risc Developments Dual MEMC2

Post by DutchAcorn » Sun Aug 23, 2020 9:46 pm

steve3000 wrote:
Sun Aug 23, 2020 9:37 pm
Good win! It's also a 33MHz ARM3 A5000a. :)
Really? It has a serial number starting with 25-ALB55, I thought that would make it a 25MHz 4MB version?
Paul

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Re: A5000 with Risc Developments Dual MEMC2

Post by steve3000 » Sun Aug 23, 2020 10:34 pm

DutchAcorn wrote:
Sun Aug 23, 2020 9:46 pm
steve3000 wrote:
Sun Aug 23, 2020 9:37 pm
Good win! It's also a 33MHz ARM3 A5000a. :)
Really? It has a serial number starting with 25-ALB55, I thought that would make it a 25MHz 4MB version?
My ALB55 certainly is 33MHz. The 25 in the serial number does not indicate the clock speed...that would be too easy! (Not sure what the 25 indicates, maybe someone knows?)

But yes ALB55 is 4mb, 33MHz. It should have a 210mb HDD too.

Also note the date code of the VIDC and crystals near the ROMs, all late 1993, which was when the A5000 alphas were made. :)

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Re: A5000 with Risc Developments Dual MEMC2

Post by IanJeffray » Sun Aug 23, 2020 11:52 pm

Well, oops. I didn't notice the dual MEMC, but I was bidding against you anyway :( There should be an "I'm bidding on" section on Stardot so we don't do this ;) If it's 8MB, that makes it a great machine.


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Re: A5000 with Risc Developments Dual MEMC2

Post by SarahWalker » Mon Aug 24, 2020 5:54 pm

IanJeffray wrote:
Mon Aug 24, 2020 5:45 pm
And put a cherry on the top: https://www.ebay.co.uk/itm//293704401471
MINE

Also it probably wouldn't work at 33 MHz anyway.

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DutchAcorn
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Re: A5000 with Risc Developments Dual MEMC2

Post by DutchAcorn » Mon Aug 24, 2020 7:21 pm

SarahWalker wrote:
Mon Aug 24, 2020 5:54 pm
IanJeffray wrote:
Mon Aug 24, 2020 5:45 pm
And put a cherry on the top: https://www.ebay.co.uk/itm//293704401471
MINE

Also it probably wouldn't work at 33 MHz anyway.
It seems to work fine in another A5000a that I recently got. At least according to Si. Perhaps an FPA11 will be even faster.

This was discussed a few years ago. See here: viewtopic.php?f=9&t=5028&p=46232#p46232
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Re: A5000 with Risc Developments Dual MEMC2

Post by IanJeffray » Tue Aug 25, 2020 12:21 am

SarahWalker wrote:
Mon Aug 24, 2020 5:54 pm
IanJeffray wrote:
Mon Aug 24, 2020 5:45 pm
And put a cherry on the top: https://www.ebay.co.uk/itm//293704401471
MINE

Also it probably wouldn't work at 33 MHz anyway.
Well -- Long ago I owned this specific A540 (Sold it to Chris...alas). It has a 33MHz ARM3 and FPA.... http://chrisacorns.computinghistory.org ... /A540.html So ... FPA10 can work with 33MHz ARM3 :)

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Re: A5000 with Risc Developments Dual MEMC2

Post by SarahWalker » Tue Aug 25, 2020 7:36 am

I was told some time ago by an ex-Acorn employee that the A540 33 MHz cards had hand-picked ARM3 and FPA10 chips that were known to work together...

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Re: A5000 with Risc Developments Dual MEMC2

Post by IanJeffray » Tue Aug 25, 2020 10:04 am

Well, memory is always fuzzy, but I'm 99% sure I bought that particular FPA10 myself (new) and it was originally in a (25MHz) IFEL PGA ARM3 board in an A310, and then moved to the A540 :) It's possible I was just incredibly lucky there. I was certainly completely naiive to any such limitation. I expect I still have the ArmSI files kicking around somewhere. This was pre-StrongARM when that A540 was still kicking the arse of the "slow, ugly" 30MHz RiscPC w/ Arm610 I was given for work :)

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Re: A5000 with Risc Developments Dual MEMC2

Post by SarahWalker » Tue Aug 25, 2020 10:22 am

I'm sure I read somewhere that the FPA10 was mostly limited to 25 MHz, hence the main point of the FPA11 was to hit 33. There was also something about the A5000 PSU being too noisy for 33 MHz FPA to be reliable. Could of course be wrong though, it's not like I was paying attention to Acorn stuff at the time!

Really though, you wanted one of these bad boys : https://acorn.huininga.nl/pub/media/pho ... 20card.JPG

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Re: A5000 with Risc Developments Dual MEMC2

Post by IanJeffray » Tue Aug 25, 2020 12:29 pm

SarahWalker wrote:
Tue Aug 25, 2020 10:22 am
Really though, you wanted one of these bad boys : https://acorn.huininga.nl/pub/media/pho ... 20card.JPG
Holy moly! Yep. I want/wanted a lot of things ;)

Found the ArmSI file from the A540, confirming 33MHz + FPA, at least. I'd forgotten the A540 was also 12MHz MEMC too. Argh! Somehow I thought that improvement was reserved for the A5000.
a540fpa.png
A540 33MHz with FPA

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Re: A5000 with Risc Developments Dual MEMC2

Post by SarahWalker » Tue Aug 25, 2020 1:16 pm

From the looks of that, a graphics card as well? Quite the beast of a machine.

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Re: A5000 with Risc Developments Dual MEMC2

Post by IanJeffray » Tue Aug 25, 2020 3:26 pm

SarahWalker wrote:
Tue Aug 25, 2020 1:16 pm
From the looks of that, a graphics card as well? Quite the beast of a machine.
Well the A540 did have a ColourCard, but that screenshot of the ArmSi window was taken on a RiscPC just now ;)

Back on topic tho - where's this A5000 going?

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Re: A5000 with Risc Developments Dual MEMC2

Post by DutchAcorn » Tue Aug 25, 2020 5:15 pm

IanJeffray wrote:
Tue Aug 25, 2020 3:26 pm
SarahWalker wrote:
Tue Aug 25, 2020 1:16 pm
From the looks of that, a graphics card as well? Quite the beast of a machine.
Well the A540 did have a ColourCard, but that screenshot of the ArmSi window was taken on a RiscPC just now ;)

Back on topic tho - where's this A5000 going?
The seller just came back with a high shipping quote which sounds like a waste, so I'm having it sent to Sarah.
Paul

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Re: A5000 with Risc Developments Dual MEMC2

Post by SarahWalker » Thu Aug 27, 2020 9:31 am

SarahWalker wrote:
Tue Aug 25, 2020 10:22 am
I'm sure I read somewhere that the FPA10 was mostly limited to 25 MHz, hence the main point of the FPA11 was to hit 33.
Stepping back to this for a second, my FPA Upgrade Pack just arrived in the post. I find this note on the first page of the installation instructions to be interesting :
The FPA may be fitted to the Acorn A5000 and A540. Note however, that the FPA10 is a 26MHz chip, and must not be installed in machines with ARM chips that run faster than 26MHz.

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Re: A5000 with Risc Developments Dual MEMC2

Post by IanJeffray » Thu Aug 27, 2020 11:03 am

SarahWalker wrote:
Thu Aug 27, 2020 9:31 am
... must not be installed in machines with ARM chips that run faster than 26MHz.
"Must not?" Do it, do it! :lol:
(Surely wouldn't kill it?....)

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Re: A5000 with Risc Developments Dual MEMC2

Post by steve3000 » Thu Aug 27, 2020 11:06 am

IanJeffray wrote:
Thu Aug 27, 2020 11:03 am
SarahWalker wrote:
Thu Aug 27, 2020 9:31 am
... must not be installed in machines with ARM chips that run faster than 26MHz.
"Must not?" Do it, do it! :lol:
(Surely wouldn't kill it?....)
I installed my FPA into my 26MHz ARM3 A540... so ticked that box!

...then I overclocked to 30MHz :)

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Re: A5000 with Risc Developments Dual MEMC2

Post by DutchAcorn » Thu Aug 27, 2020 11:17 am

It was installed in an Alpha that I have.

Si shows that it is not as fast as the A540, can the FPA10 be slowing things down?

It is an old version of Si (1991), it does not see the 8MB that is available.
F3C6A555-4E21-4FD8-9ADF-4B59EFE8B49F.jpeg
0BDACC43-2392-4E20-B0E0-0B127EED505E.jpeg

Edit: now run with FPE 4.03
Last edited by DutchAcorn on Thu Aug 27, 2020 1:06 pm, edited 1 time in total.
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Re: A5000 with Risc Developments Dual MEMC2

Post by steve3000 » Thu Aug 27, 2020 12:46 pm

DutchAcorn wrote:
Thu Aug 27, 2020 11:17 am
It was installed in an Alpha that I have.

Si shows that it is not as fast as the A540, can the FPA10 be slowing things down?

It is an old version of Si (1991), it does not see the 8MB that is available.
There were some significant changes to the test code in Si, in some versions, so you need to use the same version when comparing. Also need to use the same version of FPEmulator when comparing the FPA speed, as not all FP instructions are performed entirely by FPA10.

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Re: A5000 with Risc Developments Dual MEMC2

Post by SarahWalker » Sat Aug 29, 2020 11:22 am

So this machine arrived yesterday. It's definitely an alpha - board is marked as '4M/33MHZ'. I opened it before turning it on, which is just as well as the MEMC board and CPU oscillator had come detached (is the latter normally socketed on an alpha?). When powered on it seems to run through the self test okay, but then on I get a screen with bad sync with some unreadable text on it, and it doesn't respond to keyboard. Looking at the board, it looks like there's some battery damage, but the battery was removed before it could spread beyond the battery/CMOS area. First task is to clean off the thick layer of dust covering the board...
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a5000 battery.jpg
a5000 board.jpg

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Re: A5000 with Risc Developments Dual MEMC2

Post by flaxcottage » Sat Aug 29, 2020 12:17 pm

That looks like a job and a half you have there, Sarah. :lol:

At least the battery damage does not look too severe. It will be good to see it working.
- John

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Re: A5000 with Risc Developments Dual MEMC2

Post by SarahWalker » Sat Aug 29, 2020 12:24 pm

Well that was anticlimatic...

Jumper at LK2 was missing, which blocked the Kout signal to the keyboard. Fit that and DELETE power-on goes to the desktop.

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Re: A5000 with Risc Developments Dual MEMC2

Post by SarahWalker » Sat Aug 29, 2020 12:58 pm

Just been playing with the machine, with the exception of the missing battery the machine seems fully functional.

It looks to be a bit of a mongrel; ALB55 implies a 210 MB hard drive, but there are two here, a 40 MB and 80 MB. The 80 MB throws regular disc errors unfortunately, but the contents look like it's come from a family machines, quite a lot of photos and schoolwork and surprisingly little in the way of software. The 40 MB I think is from a teacher's home machine, quite a bit of educational stuff but also a few games.

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Re: A5000 with Risc Developments Dual MEMC2

Post by IanS » Sat Aug 29, 2020 1:03 pm

SarahWalker wrote:
Sat Aug 29, 2020 12:24 pm
Jumper at LK2 was missing, which blocked the Kout signal to the keyboard. Fit that and DELETE power-on goes to the desktop.
Simple fix, excelent. Allways good to check the simple stuff first.

Have you got any pictures of the memory/memc cards you took out. Thanks.

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Re: A5000 with Risc Developments Dual MEMC2

Post by SarahWalker » Sat Aug 29, 2020 2:14 pm

Here you go.
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8mb_2.jpg
8mb_1.jpg

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Re: A5000 with Risc Developments Dual MEMC2

Post by IanS » Sat Aug 29, 2020 2:35 pm

SarahWalker wrote:
Sat Aug 29, 2020 2:14 pm
Here you go.
Thanks, there must be som electrical connection between the boards, can you get a side view to show it?

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Re: A5000 with Risc Developments Dual MEMC2

Post by SarahWalker » Sat Aug 29, 2020 2:50 pm

Will do when I next take the machine apart again...

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