New A3000 4MB memory

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

New RAM for you?

Poll ended at Mon Sep 24, 2018 8:05 am

Yes - Quality connectors please!
9
56%
Yes - Much cheapness connectors
1
6%
Maybe - at some point...
2
13%
Narp - I have 4MB already
4
25%
Narp - I have 2MB already and it is plenty
0
No votes
Narp - I have 1MB already and it is adequate
0
No votes
 
Total votes: 16

cmorley
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New A3000 4MB memory

Post by cmorley » Sat Aug 25, 2018 8:05 am

I got an A3000 this week with a 2MB of RAM in it. Pfft! Being more interested in making upgrades for computers than using them I'm going to do a 4MB memory upgrade for an A3000 using brand new parts (not ancient stock or recycled chips from parts unknown).

If I am making one then I can make more but I'd like to get a straw poll of interest.

I think they will be circa £40 with quality gold tin connectors or maybe £35 with cheap connectors from the land of the rising sun. Sadly the RAM chips are really rather expensive :( It depends a bit on numbers...
Last edited by cmorley on Sat Aug 25, 2018 10:56 am, edited 1 time in total.

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IanS
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Re: New A3000 4MB memory

Post by IanS » Sat Aug 25, 2018 10:22 am

I don't think the pins on the A3000 motherboard are gold-plated, does that cause a problem with dissimilar metals?

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Re: New A3000 4MB memory

Post by cmorley » Sat Aug 25, 2018 10:54 am

IanS wrote:
Sat Aug 25, 2018 10:22 am
I don't think the pins on the A3000 motherboard are gold-plated, does that cause a problem with dissimilar metals?
Thanks good call..... the connector manufacturer does a Tin plated version which will be better then.

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Re: New A3000 4MB memory

Post by johnkenyon » Sat Aug 25, 2018 1:10 pm

Are any 72pin SIMMs electrically compatible?

/John
Last edited by johnkenyon on Sat Aug 25, 2018 1:10 pm, edited 1 time in total.

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Re: New A3000 4MB memory

Post by daveejhitchins » Sat Aug 25, 2018 1:16 pm

IanS wrote:
Sat Aug 25, 2018 10:22 am
I don't think the pins on the A3000 motherboard are gold-plated, does that cause a problem with dissimilar metals?
Doubt it . . . Does anything react with Gold - where are our Metallurgists?

Dave H :D
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Re: New A3000 4MB memory

Post by cmorley » Sat Aug 25, 2018 2:53 pm

daveejhitchins wrote:
Sat Aug 25, 2018 1:16 pm
IanS wrote:
Sat Aug 25, 2018 10:22 am
I don't think the pins on the A3000 motherboard are gold-plated, does that cause a problem with dissimilar metals?
Doubt it . . . Does anything react with Gold - where are our Metallurgists?
Gold-Tin is not ideal long term as IanS pointed out. The gold won't corrode but there is an increase chance the tin plating on the pins will if in a humid environment. Is it much of a problem? Kinda moot though since I can get a tin plated version of the same connector for the same money - might as well just fit the tin one. :)

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Re: New A3000 4MB memory

Post by cmorley » Sat Aug 25, 2018 2:55 pm

johnkenyon wrote:
Sat Aug 25, 2018 1:10 pm
Are any 72pin SIMMs electrically compatible?
Fast Page Mode (FPM) should be. Since the A3000 doesn't interleve memory banks EDO _might_ work in it too. I have some EDO I might try it on a board just for kicks.

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Re: New A3000 4MB memory

Post by IanS » Sat Aug 25, 2018 4:12 pm

johnkenyon wrote:
Sat Aug 25, 2018 1:10 pm
Are any 72pin SIMMs electrically compatible?
Ifel made it work in the past - http://chrisacorns.computinghistory.org ... 4K4MB.html

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Re: New A3000 4MB memory

Post by johnkenyon » Sat Aug 25, 2018 6:42 pm

cmorley wrote:
Sat Aug 25, 2018 2:55 pm
johnkenyon wrote:
Sat Aug 25, 2018 1:10 pm
Are any 72pin SIMMs electrically compatible?
Fast Page Mode (FPM) should be. Since the A3000 doesn't interleve memory banks EDO _might_ work in it too. I have some EDO I might try it on a board just for kicks.
The reason I asked was because I've got a load of 72pin 4Mb SIMMs sat in a box and this looks like a good cause to donate them to, either for plugging into an adaptor or for someone to do some SMD component recovery and reuse the memory.

/jjohn

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Re: New A3000 4MB memory

Post by cmorley » Sun Aug 26, 2018 9:37 pm

Prototype PCBs ordered. They should be here in a couple of weeks. I'll post an update when they arrive.

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Re: New A3000 4MB memory

Post by cmorley » Mon Aug 27, 2018 9:38 am

I've just done the cost of goods calculation.

There is enough interest in the poll so far to buy the RAM chips in greater bulk so the price is a bit lower.

£35 for forum members with the quality Sullins connectors. (£32 if you want cheap connectors - they are only 10p each! :S )

Here is the sales thread to register interest & pre-order: viewtopic.php?f=8&t=15589
Please post all sales/purchase queries on that thread not here. Please post any technical questions or comments here. :)

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Re: New A3000 4MB memory

Post by IanS » Mon Aug 27, 2018 10:30 am

Can you post any pcb layouts/schematics, would be interesting to see how it looks?

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Re: New A3000 4MB memory

Post by cmorley » Mon Aug 27, 2018 12:36 pm

IanS wrote:
Mon Aug 27, 2018 10:30 am
Can you post any pcb layouts/schematics, would be interesting to see how it looks?
Board view from the CAD. I didn't quite manage to route everything on the top :(
18.010_3d.png
Edit:
The holes are so you can loop some string/cable ties/hook through and pull it out! I've found removing the BITD ones a real pain.

It is so small I didn't bother with copying the metal mounting bracket. If the market was hundreds then I'd have looked at that.
Last edited by cmorley on Mon Aug 27, 2018 12:39 pm, edited 2 times in total.

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Re: New A3000 4MB memory

Post by IanS » Mon Aug 27, 2018 1:38 pm

Capacitors on the other side? double sided load?

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Re: New A3000 4MB memory

Post by cmorley » Mon Aug 27, 2018 1:58 pm

Yes. 6x 0805 caps ceramic caps on the backside. One for each power pin. It shouldn't need any additional bulk capacitance. (If I'm wrong I'll add some for the production boards)

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Re: New A3000 4MB memory

Post by Lardo Boffin » Tue Aug 28, 2018 1:24 pm

cmorley wrote:
Sat Aug 25, 2018 8:05 am
Being more interested in making upgrades for computers than using them I'm going to do a 4MB memory upgrade for an A3000 using brand new parts (not ancient stock or recycled chips from parts unknown).
At the risk of going completely off this topic how about a modern remake of the 4MHz solidisk board for the model B? We have superfast co-procs available now but nothing to make the main board go faster. A 4MHz boost would be in keeping with the original machine as it was available BITD. :D
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Re: New A3000 4MB memory

Post by cmorley » Tue Aug 28, 2018 1:57 pm

Lardo Boffin wrote:
Tue Aug 28, 2018 1:24 pm
At the risk of going completely off this topic how about a modern remake of the 4MHz solidisk board for the model B? We have superfast co-procs available now but nothing to make the main board go faster. A 4MHz boost would be in keeping with the original machine as it was available BITD. :D
It's in the pipeline. I made a CPU socket adapter for the 2nd co-pro board I made (8 bit thread).

I will post in 8 bit hardware when I start work on it in the next few weeks.

Chris

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Re: New A3000 4MB memory

Post by 1024MAK » Tue Aug 28, 2018 2:58 pm

daveejhitchins wrote:
Sat Aug 25, 2018 1:16 pm
IanS wrote:
Sat Aug 25, 2018 10:22 am
I don't think the pins on the A3000 motherboard are gold-plated, does that cause a problem with dissimilar metals?
Doubt it . . . Does anything react with Gold - where are our Metallurgists?

Dave H :D
I'm not a Metallurgist. But I do have some experience of gold plated contacts in contact with tin plated contacts.

Some equipment that we maintain and trouble shoot at work has this arrangement. The equipment lives in steel metal (some are stainless steel) enclosures in the great British outdoors. So although fully protected from rain, if the air outside is humid, the air inside may also be humid. I'm talking about hundreds of installations just in the area that we (one depot) cover.

At random intervals, some installations will indicate a problem. So about every month or sometimes every week, we have to go and service the one that is not happy.

Most of the time, it's the same high-resistance contact problem. The gold plated contacts are fine after a quick wipe, but it's possible to see a white power like substance that has build up on the tin contact. The fix in most cases is just to disconnect and reconnect about ten times. This action cleans the contact surfaces and away it goes for about another four to ten months...

Or instead we try the official fix - renew the module. But it's the module that has the gold plated contacts...

Mark

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Re: New A3000 4MB memory

Post by Lardo Boffin » Tue Aug 28, 2018 3:28 pm

cmorley wrote:
Tue Aug 28, 2018 1:57 pm
Lardo Boffin wrote:
Tue Aug 28, 2018 1:24 pm
At the risk of going completely off this topic how about a modern remake of the 4MHz solidisk board for the model B? We have superfast co-procs available now but nothing to make the main board go faster. A 4MHz boost would be in keeping with the original machine as it was available BITD. :D
It's in the pipeline. I made a CPU socket adapter for the 2nd co-pro board I made (8 bit thread).

I will post in 8 bit hardware when I start work on it in the next few weeks.

Chris
Excellent! I was not expecting that. :shock:
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Re: New A3000 4MB memory

Post by cmorley » Tue Sep 04, 2018 9:25 am

Update: Prototype PCBs are on the way from China.

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Re: New A3000 4MB memory

Post by aotta » Tue Sep 04, 2018 10:27 pm

So, in a couple of months they will arrive! :lol:

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Re: New A3000 4MB memory

Post by Cutter » Sun Sep 09, 2018 8:15 pm

Slightly dumb question, but is this board one which will fit perpendicular to, or parallel with, the motherboard?

I ask because if the former (and it looks from your schematic that it is), that's great, but if the latter, it will foul a recently fitted Arm3 on my motherboard...

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Re: New A3000 4MB memory

Post by cmorley » Sun Sep 09, 2018 8:27 pm

It's designed to go perpendicular to the main board.

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Re: New A3000 4MB memory

Post by Cutter » Sun Sep 09, 2018 8:36 pm

:D

Thank you. Just lost my 1MB cumana RAM upgrade board due to having an Arm 3 fitted to my A3000, so your RAM board looks great!

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Re: New A3000 4MB memory

Post by cmorley » Tue Sep 11, 2018 4:25 pm

The prototype PCBs arrived. I've soldered one up and it worked first time :S

I haven't fitted any of the decoupling caps for a worse case test.

Does anyone have a continuous running memory test or suggestion of an application which really hammers the memory? I have Goteks so a disk image would be helpful...

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Re: New A3000 4MB memory

Post by IanS » Tue Sep 11, 2018 6:48 pm

cmorley wrote:
Tue Sep 11, 2018 4:25 pm
The prototype PCBs arrived. I've soldered one up and it worked first time :S

I haven't fitted any of the decoupling caps for a worse case test.

Does anyone have a continuous running memory test or suggestion of an application which really hammers the memory? I have Goteks so a disk image would be helpful...
Not as convienient as a disk image, but the test roms should work on an A3000, which have a ram test mode.
viewtopic.php?f=16&t=12252&p=155802#p155802

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Re: New A3000 4MB memory

Post by lcww1 » Tue Sep 11, 2018 7:19 pm

There’s a RAM test program in the A3000 Acorn dealer test disc here - http://www.lewisgilbert.co.uk/archiolog ... discs.html - I’ve not had a chance to look at this in any detail, so may not be useful for testing RAM expansion.

If the ROMs or dealer test disc aren’t suitable for test purposes, then perhaps running a memory hungry game would be an alternative? Not sure which A3000 games would need or use 4Mb of RAM though....

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Re: New A3000 4MB memory

Post by cmorley » Wed Sep 12, 2018 5:09 pm

I ran a bunch of different games I have (I only have a small library of software for the A3000) and nothing skipped a beat so far. I made RAM disks and copied games to that and ran them from there to get the memory usage up.

So far so good :)

It is also amusing to slide the "next" up to max and start BASIC with 3.6MB free. Impressive compared to a B but then I remember that the laptop I'm using now has 16GB of RAM...

I'll do a bit more testing and order the nice connectors from digikey and build up another board to the spec I intend to ship.

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Re: New A3000 4MB memory

Post by cmorley » Wed Sep 12, 2018 5:24 pm

Pictures! :D

Installed with the cheapo chinese connectors (nice connectors not in yet):
Photo0747.jpg
Installed:
Photo0749.jpg
Bare boards:
Photo0750.jpg
Chips - enough to cover those who've put their names down:
Photo0751.jpg
It works:
Photo0754.jpg
Bits awaiting assembly - bench needs a tidy :S :
Photo0755.jpg

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Re: New A3000 4MB memory

Post by aotta » Wed Sep 12, 2018 7:54 pm

Great works! And your desk is in great order compared to my kitchen! (My Amiga 600 still doesn't boot.. I must move soldering station elsewhere ...) :lol:

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