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Author Topic: Internal memory expansion (Read 252312 times)

Offline Wolfgang

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Re: Internal memory expansion
« Reply #285 on: 2020.September.13. 15:04:01 »
As I am new to EP (yes I got my EP64 from Egypt), I followed this great thread and built my own memory extension (prototype). I am using a GAL16V8 for address decoding and a AS6C4008 SRAM chip.
I just finished my prototype and at least the boot screen seems to work. It is a bit scary to unplug and reconnect the  keyboard membrane since it seems to be very thin, so no real tests yet.
« Last Edit: 2020.September.13. 16:48:46 by Wolfgang »
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Offline elmer

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Re: Internal memory expansion
« Reply #286 on: 2020.September.13. 19:03:20 »
Quote from: Wolfgang on 2020.September.13. 15:04:01
As I am new to EP (yes I got my EP64 from Egypt), I followed this great thread and built my own memory extension (prototype). I am using a GAL16V8 for address decoding and a AS6C4008 SRAM chip.
I just finished my prototype and at least the boot screen seems to work. It is a bit scary to unplug and reconnect the  keyboard membrane since it seems to be very thin, so no real tests yet.

Congratulations! It is excellent to see another successful breadboard circuit, just like Dangerman's pictures a few pages ago. :)

I see that you have added a header to EXP2 instead of wiring the cable directly into the motherboard ... how is that working out for you?

I was under the impression that there isn't enough physical height inside the case at that point for a header and DuPont connectors, which is why SainT and the others wired the cable directly into the motherboard.

Have I misunderstood the earlier posts?

It would certainly be easier to use 2 5-pin DuPont cables instead of soldering the wires directly into the motherboard.
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Offline Wolfgang

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Re: Internal memory expansion
« Reply #287 on: 2020.September.13. 19:55:53 »
Quote from: elmer on 2020.September.13. 19:03:20
Congratulations! It is excellent to see another successful breadboard circuit, just like Dangerman's pictures a few pages ago. :)

I see that you have added a header to EXP2 instead of wiring the cable directly into the motherboard ... how is that working out for you?

I was under the impression that there isn't enough physical height inside the case at that point for a header and DuPont connectors, which is why SainT and the others wired the cable directly into the motherboard.

Have I misunderstood the earlier posts?

It would certainly be easier to use 2 5-pin DuPont cables instead of soldering the wires directly into the motherboard.

Thanks. Unfortunately, I was too optimistic about EXP2. I can close the top, but it bends the plastic out about 1mm. I will remove the header or at least the front row and solder the cables directly. Btw., I was not able to use a standard double-row header on EXP1. It seems the distance between the two rows is off. I used two single rows instead.
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Offline elmer

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Re: Internal memory expansion
« Reply #288 on: 2020.September.13. 21:12:11 »
Quote from: Wolfgang on 2020.September.13. 19:55:53
Unfortunately, I was too optimistic about EXP2. I can close the top, but it bends the plastic out about 1mm.

That's good to know, I'm sorry that you found out the hard way! ;)


Quote from: Wolfgang on 2020.September.13. 19:55:53
Btw., I was not able to use a standard double-row header on EXP1. It seems the distance between the two rows is off. I used two single rows instead.

I saw that you've used the male header on the motherboard's EXP1, rather than the female header (which is how SainT's board seems to usually be installed) ... I wonder if that has anything to do with the distance problem.

The solder tails on a female header are usually a bit thinner and more flexible than the solder tails on a male header.
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Offline Wolfgang

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Re: Internal memory expansion
« Reply #289 on: 2020.September.14. 18:25:43 »
I removed the header. Now I can close it properly. :)
I also replaced the 7805s with OKI-78SR; quite the difference now......
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Offline elmer

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Re: Internal memory expansion
« Reply #290 on: 2020.September.15. 21:01:03 »
Quote from: Wolfgang on 2020.September.14. 18:25:43
I also replaced the 7805s with OKI-78SR; quite the difference now......

That's a neat little replacement for the 7805! :)

Why did you make the change? Were you having problems with your EP64?
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Offline Wolfgang

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Re: Internal memory expansion
« Reply #291 on: 2020.September.15. 21:38:12 »
Quote from: elmer on 2020.September.15. 21:01:03
That's a neat little replacement for the 7805! :)

Why did you make the change? Were you having problems with your EP64?

It is more of a habit. I usually replace every 7805 in old computers either with the OKI-78SR or the TSR 1-2450 in order to reduce the heat. I generally prefer the TSR 1-2450, but they don't fit in the EP without removing the cooler and that would leave an ugly hole.
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Offline gflorez

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Re: Internal memory expansion
« Reply #292 on: 2020.September.16. 03:41:25 »
The TracoPower can be installed(TSR 1-2450, or even better the 2 Amp TSR 2-2450), I did it on one of my EPs, but some bending has to be done on its little pins.
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Offline Wolfgang

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Re: Internal memory expansion
« Reply #293 on: 2020.September.16. 08:10:41 »
Quote from: gflorez on 2020.September.16. 03:41:25
The TracoPower can be installed(TSR 1-2450, or even better the 2 Amp TSR 2-2450), I did it on one of my EPs, but some bending has to be done on its little pins.
This worked for me with the front regulator, but not for the rear one. The space between the power connector and the cooler was too small to get the Traco in. May this is only be an ISSUE 4 problem?
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Offline dangerman

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Re: Internal memory expansion
« Reply #294 on: 2020.September.16. 10:34:15 »
Quote from: Wolfgang on 2020.September.13. 19:55:53
Unfortunately, I was too optimistic about EXP2. I can close the top, but it bends the plastic out about 1mm.

Yes - I found that out the hard way too :(

Quote from: Wolfgang on 2020.September.13. 19:55:53
Btw., I was not able to use a standard double-row header on EXP1. It seems the distance between the two rows is off. I used two single rows instead.

I had forgotten this, but I remember having a slight problem too! I seem to recall that the official boards in the EP128 are directly attached by 28 individual tall pins, so for them the off-spacing wasn't a problem.
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Offline emptiness

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Re: Internal memory expansion
« Reply #295 on: 2020.September.18. 07:46:17 »
Quote from: Wolfgang on 2020.September.15. 21:38:12
It is more of a habit. I usually replace every 7805 in old computers either with the OKI-78SR or the TSR 1-2450 in order to reduce the heat. I generally prefer the TSR 1-2450, but they don't fit in the EP without removing the cooler and that would leave an ugly hole.

Thanks for this. I suspect there is an issue with one of the 7805s on my enterprise and was planning to replace both with new 7805s but will use OKI-78SR now.
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Offline emptiness

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Re: Internal memory expansion
« Reply #296 on: 2020.September.27. 22:52:24 »
Quote from: elmer on 2020.September.10. 23:38:43
The boards have arrived from China ... now I've got to wait for the headers to arrive, and then I've still got to wire up an RGB cable for my monitor before I can actually make sure that these work (or not)! ;)

(Attachment Link)

Any luck? Did the expansion work?
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Offline elmer

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Re: Internal memory expansion
« Reply #297 on: 2020.September.28. 17:01:35 »
Quote from: emptiness on 2020.September.27. 22:52:24
Any luck? Did the expansion work?

Sorry, there have been many distractions. I still haven't wired up my video cable, which I need to do before seeing if the memory boards work.

Hopefully I'll know soon.
« Last Edit: 2020.September.28. 18:47:44 by elmer »
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Offline Wolfgang

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Re: Internal memory expansion
« Reply #298 on: 2020.September.28. 17:21:58 »
Not to compete with the professionals here, but as a personal learning experience, I also created a pcb of my GAL based SRAM solution. It was a pain to create (I used KiCad) since I have never done anything like this before. Now I am really nervous if this is going to work at all. :roll:
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Offline elmer

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Re: Internal memory expansion
« Reply #299 on: 2020.September.28. 19:21:10 »
Quote from: Wolfgang on 2020.September.28. 17:21:58
Now I am really nervous if this is going to work at all. :roll:

Hahaha ... me too with my board! ;)
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