Amiga hardware info, help and support with a focus (but not limited to) North American NTSC experiences. Open to all.
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intric8
Seattle, WA, USA

by intric8 posted Tue Dec 11, 2018 8:50 pm

I pulled the images down to host them and embedded them. All good now. (and yeah, those original URLs were gigantic!)

I've never seen an A1000 daughterboard like this before.

I wonder what the heck that upgrade (or repair) is all about? Fascinating.
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A10001986

by A10001986 posted Wed Dec 12, 2018 3:22 am

JEY08 wrote:The problem is that it only shows 256K of chip ram and 512K of fast ram. The front memory isn't there.


Where is that 512k of fast RAM coming from? Anything connected externally? The stock A1000 does not have any internal memory other than 256k (+256k via A1050 or compatible) of chip RAM.

(Uneducated guess: I don't see enough chips added on the piggyback to make up 512k, the 74F08 is no RAM, and the other one is not recognizable)

Edit: In one of your follow-ups you state that the machine couldn't load kickstart - how did you determine the amount of detected RAM without loading kickstart?

Edit 2: Looking at the clearly non-original EPROMs on the main board, I come to think that the hack on the piggyback is rather odd. What is in those EPROMs? Does the machine show a hand with "Workbench" or "Kickstart" upon power-on? If that is in fact a kickstart in those EPROMs that piggyback hack might be in order to use the WOM as RAM...)? However, that would only account for 256k, not 512k.... perhaps the second 256k of chip ram are falsely addressed in a fast RAM area... Odd... How much RAM does the machine show when you remove the front expansion?
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intric8
Seattle, WA, USA

by intric8 posted Wed Dec 12, 2018 9:12 am

I posted your pics to some folks on Facebook last night for ideas.

I got a few interesting comments.

Christian Stich noted that it did not look like the original piggyback RAM hack designed by Cris Erving and described in the 1987 Amazing Computing magazine. (Post with several page scans.)
Screen Shot 2018-12-12 at 9.12.05 AM.png

Screen Shot 2018-12-12 at 9.11.33 AM.png


Robert Miranda said:
Mods to the daughter card were needed if one did a ROM hack (vs soft load). I have done them before. But it’s been a while. There was a separate hack that remapped the wcs ram as fastram in addition to the ROM hack. The current day KS ROM hack just disables the old memory.


Not sure if any of this helps or jogs a memory of yours, but just in case.
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rpiguy9907

by rpiguy9907 posted Wed Dec 12, 2018 9:35 am

Well it looks to me like your system is recognizing the front 256KB of RAM.

What you have is a mod that doubles the internal memory to 512K and wires it up to be FAST RAM. The piggy backed RAM is a giveaway.

Look at the photos of the RAM. The daughter card is irrelevant. What matters is that it looks like the original RAM chips on the MB were either replaced with higher capacity or there are literally two chips stacked on top of one another.
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JEY08
Bath, MI

by JEY08 posted Wed Dec 12, 2018 10:44 am

The problem with the floppy drive was only momentary.

The memory hack is 2 each HM50464P 64Kx4 DRAM chips stacked together and in turn stacked on the existing memory on the motherboard giving an additional 512k of memory.

I only see 256K beyond the 512K. I see that whether I have the front memory installed or not.
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intric8
Seattle, WA, USA

by intric8 posted Wed Dec 12, 2018 11:24 am

OK very cool. I'll get this front expansion sent your way stat.

Mattsoft had a cool idea while pondering your system:
It would be cool to take your daughterboard and put it on a known fully working system and see what happens just to get a benchmark.
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rpiguy9907

by rpiguy9907 posted Wed Dec 12, 2018 4:03 pm

JEY08 wrote:The problem with the floppy drive was only momentary.

The memory hack is 2 each HM50464P 64Kx4 DRAM chips stacked together and in turn stacked on the existing memory on the motherboard giving an additional 512k of memory.

I only see 256K beyond the 512K. I see that whether I have the front memory installed or not.


If you have stacked 64Kx4 two high then you do not have an additional 512K RAM right?

This should give you 768K with the front RAM expansion installed and 512K without it.

Or are you claiming that you have stacks that are three high?! If so wow I’ve never seen that. Cool!
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JEY08
Bath, MI

by JEY08 posted Wed Dec 12, 2018 6:35 pm

rpiguy9907 wrote:
JEY08 wrote:The problem with the floppy drive was only momentary.

The memory hack is 2 each HM50464P 64Kx4 DRAM chips stacked together and in turn stacked on the existing memory on the motherboard giving an additional 512k of memory.

I only see 256K beyond the 512K. I see that whether I have the front memory installed or not.


If you have stacked 64Kx4 two high then you do not have an additional 512K RAM right?

This should give you 768K with the front RAM expansion installed and 512K without it.

Or are you claiming that you have stacks that are three high?! If so wow I’ve never seen that. Cool!

Two chips were added to the top of the existing ones.
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JEY08
Bath, MI

by JEY08 posted Wed Dec 12, 2018 6:50 pm

I've been looking at the daughterboard modification. It appears to be intended to eliminate the need for the make512 and addmen 80000 FFFFF commands. It seems to configure the added memory starting at C00000 and doesn't try to make it chip ram.

Inspecting mh_Upper shows C7E800 so that seems to confirm it.

I'll make a schematic of the modification when I get time. Then you guys can look at it and tell me if it does what I think it does.
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rpiguy9907

by rpiguy9907 posted Wed Dec 12, 2018 9:02 pm

Thanks for clarifying on my phone it looked like two chips and a socket, not three chips. Makes sense now.

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