A500 trapdoor memory: free design - Page 5

Mathesar · 02 July 2017, 20:17

The new board came in and it works great. The system is now 100% stable with 1.0MB chip and 1.5MB slow. See attached picture. I also attached the full KiCad project for those who want to tinker with it.

The SO pads are indeed a bit short for hand soldering. With a bit of patience it is doable though. I did not anticipate anything other than turned pins for the IC socket. I used turned pins and they fit great.

If anyone is interested drop me a PM. I have more boards left.

Just to be clear, this rev C Gary adapter is only needed when you want 1.0MB chip and 1.5MB slow. If you only want 1.5MB slow the original rev B adapter works good enough.

Jope · 03 July 2017, 07:56

Great stuff :-)

PeteAU · 03 July 2017, 16:05

Quote:

Originally Posted by Mathesar

The new board came in and it works great. The system is now 100% stable with 1.0MB chip and 1.5MB slow. See attached picture. I also attached the full KiCad project for those who want to tinker with it.

The SO pads are indeed a bit short for hand soldering. With a bit of patience it is doable though. I did not anticipate anything other than turned pins for the IC socket. I used turned pins and they fit great.

If anyone is interested drop me a PM. I have more boards left.

Just to be clear, this rev C Gary adapter is only needed when you want 1.0MB chip and 1.5MB slow. If you only want 1.5MB slow the original rev B adapter works good enough.

Yes I would like one

Do you think we can splice the base board and your adapter into one gerber so people can get them made for peanuts? Because 10x10cm boards are dirt cheap.

Next challenge: An A500+ gary adapter to allow the first 2 drams to be chip ram and the next 2 to be slow ram. I don't know if it's even possible to have slow ram on the 500+.

Mick · 06 July 2017, 15:29

I noticed the 512KB version of this on Ebay, great work it's very interesting to see the progress hopefully the full blown version will become available for sale.

One thing I wondered is that is there any reason to have more than 512KB of slow memory? I understand that some old software needs it for compatibility reasons but would you not be best of with as little slow memory as possible and install real fast memory instead? or is there software that specifically needs more than 512KB of slow memory?

Jope · 06 July 2017, 15:55

I doubt there is anything that would really need more than 512k of Slow RAM, but then again if you can expand it as far as possible with the minimum of effort, why not. :-)

demolition · 06 July 2017, 16:22

Yes, 1MB chip+1.8MB slow+8MB fast is better than 1MB chip+0.5MB slow+8MB fast.

If the computer has fast mem, this will always be used ahead of slow mem since it has higher priority when talking OS friendly stuff. I don't know if maybe Action Replay can take advantage of using the upper slow mem since a game is very unlikely to utilize this?

Mick · 06 July 2017, 16:41

I see, I suppose as well then it was useful for A500 owners in the days when fast memory was super expensive. I used to have a 500+ with 2MB chip so the whole fast/slow memory thing mostly passed me by.

Mathesar · 07 July 2017, 18:06

Quote:

Originally Posted by Jope

I doubt there is anything that would really need more than 512k of Slow RAM, but then again if you can expand it as far as possible with the minimum of effort, why not. :-)

For me the main attraction of this RAM board is the DIY element. You can make this board from some recycled SIM sticks and a few TTL chips. And that is just fun

Most fast RAM boards are way more complicated and also often need some CPLD's or GAL's programmed.

emiespo · 10 July 2017, 01:41

Hi there,

This project is awesome, I would buy the 1meg version, but first I have one question: would a version with 2meg fast + adapter + 1 meg chip work in A500+ with an A590 board with 2 megabytes installed? Or the other FAST RAM would have an address collision?

My goal is to have a WHDLoad box as close as the "original thing" as possible, thanks! :-)

Jope · 10 July 2017, 08:18

The trapdoor Fast RAM is in a different part of the address space, so it would work ok together with the 590.

PeteAU · 10 July 2017, 12:59

Quote:

Originally Posted by emiespo

Hi there,

This project is awesome, I would buy the 1meg version, but first I have one question: would a version with 2meg fast + adapter + 1 meg chip work in A500+ with an A590 board with 2 megabytes installed? Or the other FAST RAM would have an address collision?

My goal is to have a WHDLoad box as close as the "original thing" as possible, thanks! :-)

The adapter doesn't work in a A500+ though, even Mathesar's improved one. It's meant only for a normal A500.

Jope · 10 July 2017, 13:12

Ah, didn't think it through.

Yet another gary board needed. ;-)

katarakt · 20 July 2017, 18:08

Quote:

Originally Posted by PeteAU

EDIT: More RAM details: The memory you are searching for is 72-pin, so try that as a search term on Ebay. Technically, the chips are called SOJ42, 1M x 16. You can identify them visually, they are the bigger/longer chips. If you count 21 pins on one side (42 total), it's a winner.
//Pete.

I have the PCB with gary adapter and want to solder this memory expansion. Now, i've ordered some old rams...21 pin (42 total) ...this should be the correct one?

PeteAU · 21 July 2017, 03:04

Quote:

Originally Posted by katarakt

I have the PCB with gary adapter and want to solder this memory expansion. Now, i've ordered some old rams...21 pin (42 total) ...this should be the correct one?

They look perfectly good. 8 rams per Simm? You are lucky.

katarakt · 21 July 2017, 13:31

Thanks for reply. Yes 8 rams per 16MB-simm (front 4, back 4 = total 8), so each ram should be 2MB ...is this 1X32 ? Are you sure they will work? ...i first thought i bought the wrong simms. I've only checked that they have 21 pins (42).

PeteAU · 21 July 2017, 13:48

Quote:

Originally Posted by katarakt

..is this 1X32 ?

No, it's 1M x 16.

Quote:

Originally Posted by katarakt

Thanks for reply. Yes 8 rams per 16MB-simm (front 4, back 4 = total 8), so each ram should be 2MB ...is this 1X32 ? Are you sure they will work? ...i first thought i bought the wrong simms. I've only checked that they have 21 pins (42).

That's right, each chip is 2MB (1Mx16-bit). You're using exactly the same SIMM as mine, just a different brand of chips on board.

katarakt · 21 July 2017, 17:31

Excellent!

A few questions:

1. How does it work if i want to disable the memory expansion with gary adapter? On the memory expansion there is an enable switch, i think to disable it...so...if i'm disabling the memory expansion, is the gery adapter disabled too? Someone said after disabling his memory expansion his amiga still shows 1,5mb whether the memory expansion is disabled or not.

2. Next question, can you provide the eagle files only from the memory expansion without the gery adapter? This would be fantastic, so everyone can use the rev.C gary adapter and rev B from the memory expansion and can choose if he only wants the memory expansion without the gary adapter (gary adapter is not always needed).

3. C12 you wrote 4,7 uF tantalum capacitor but in eagle layout there is written 100nf ...so what is correct? If 4,7uF tantalum is correct, you should change this part to 1210 because 0805 is very rare for this component, can't get this for cheap money.

PeteAU · 24 July 2017, 15:15

Quote:

Originally Posted by katarakt

Excellent!

A few questions:

1. How does it work if i want to disable the memory expansion with gary adapter? On the memory expansion there is an enable switch, i think to disable it...so...if i'm disabling the memory expansion, is the gery adapter disabled too? Someone said after disabling his memory expansion his amiga still shows 1,5mb whether the memory expansion is disabled or not.

2. Next question, can you provide the eagle files only from the memory expansion without the gery adapter? This would be fantastic, so everyone can use the rev.C gary adapter and rev B from the memory expansion and can choose if he only wants the memory expansion without the gary adapter (gary adapter is not always needed).

3. C12 you wrote 4,7 uF tantalum capacitor but in eagle layout there is written 100nf ...so what is correct? If 4,7uF tantalum is correct, you should change this part to 1210 because 0805 is very rare for this component, can't get this for cheap money.

1. JP4 on the adapter can disable it.

2. I didn't make such a file. Maybe one day I'll join Mathesar's adapter and the original board into one gerber. Removing the adapter doesn't save you any money though, 10x10 boards tend to be the same price as 10x5.

3. Put in a >= 2.2uF ceramic. I think I measured that 1uF isn't enough, but 2.2uF was more than enough.

katarakt · 24 July 2017, 19:40

Ok, thanks PeteAU

It's totally still confusing because BOM #61 and BOM RTC#14 are different to some eagle layout infos.

In eagle sch layout there says C11 is tantal (without value) and C12 is 100nf and RTC info #14 says tantal C12 ???

Would be great if you can give us a corrected detailed BOM, what means "* Lots of 100nF 0805 X7R capacitors" ?....can i use everywehre 100nf except the ones you wrote in parts list for RTC?

I'm still confused

....so here is the not correct old complete "BOM" from #14 and #61:

* Lots of 100nF 0805 X7R capacitors

For 512K:
* 1 x 1Mx16bit SOJ42 DRAM
* 1 x 56pin (2x28) 2.54mm double row right-angle header (or 2x40pin and cut it)

For A500+ 1MB:
* one more DRAM

For Gary Adapter:
* more DRAMs (any number you want)
* 1 x 74F139 (surface mount) (or maybe 74LS139 is fast enough)
* 2 x 74F00 (surface mount) (or maybe 74LS00 is fast enough)
* 3 x 3-pin jumper headers
* 3 x jumpers
* 2 x 24-pin DIP sockets
* 2 x round pin strips
* Wires and some 2 and 3-pin 2.54mm connectors of your choice (see my photos from previous page).

The parts list for RTC:

U4: OKI M6242B (I got some second hand ones from AliExpress for $2)
Y1: 32.768KHz MC306 crystal
C10: 100K 0805 resistor
C13: 100nF 0805 capacitor
C12: 4.7uF 10V 0805 tantalum capacitor
R1, R2, R3: 10K 0805 resistor
R4, R5: 330-470 0805 resistor
D1: BAT721C or BAT54C diode
C14,C15: 22pF 0805 capacitor
Battery Holder: Some cheap ebay one.

Alternatively, get a RTC-62421/72421 and you can leave off Y1, C14, C15. It makes it simpler.

PeteAU · 25 July 2017, 05:53

Quote:

Originally Posted by katarakt

* Lots of 100nF 0805 X7R capacitors

There's enough pads to put 1, 2 or 3 decoupling caps for each DRAM chip. I'm not going to scientifically measure how many you need, but probably 2 per chip is plenty.
So populate C1, C2, C4, C5, C7, C8, C21, C22 with 100nF.

Quote:

Originally Posted by katarakt

The parts list for RTC:

U4: OKI M6242B (I got some second hand ones from AliExpress for $2)
Y1: 32.768KHz MC306 crystal
C10: 47K-100K 0805 resistor (yes a resistor!)
C13: 100nF 0805 capacitor
C12: >=2.2uF 10V 0805 tantalum or ceramic capacitor
R1, R2, R3: 10K 0805 resistor
R4, R5: 220-470 0805 resistor
D1: BAT721C or BAT54C diode
C14,C15: 22-27pF 0805 capacitor
Battery Holder: Some cheap ebay one.

Alternatively, get a RTC-62421/72421 and you can leave off Y1, C14, C15. It makes it simpler.

Ignore the eagle file, the above BOM is good. Even C10 as a resistor is right.

06 July 2017, 15:29	#84
Mick Registered User Join Date: Jan 2004 Location: Yorkshire Posts: 710	I noticed the 512KB version of this on Ebay, great work it's very interesting to see the progress hopefully the full blown version will become available for sale. One thing I wondered is that is there any reason to have more than 512KB of slow memory? I understand that some old software needs it for compatibility reasons but would you not be best of with as little slow memory as possible and install real fast memory instead? or is there software that specifically needs more than 512KB of slow memory? Last edited by Mick; 06 July 2017 at 15:36.

21 July 2017, 17:31	#97
katarakt Registered User Join Date: Jul 2017 Location: Germany Posts: 205	Excellent! A few questions: 1. How does it work if i want to disable the memory expansion with gary adapter? On the memory expansion there is an enable switch, i think to disable it...so...if i'm disabling the memory expansion, is the gery adapter disabled too? Someone said after disabling his memory expansion his amiga still shows 1,5mb whether the memory expansion is disabled or not. 2. Next question, can you provide the eagle files only from the memory expansion without the gery adapter? This would be fantastic, so everyone can use the rev.C gary adapter and rev B from the memory expansion and can choose if he only wants the memory expansion without the gary adapter (gary adapter is not always needed). 3. C12 you wrote 4,7 uF tantalum capacitor but in eagle layout there is written 100nf ...so what is correct? If 4,7uF tantalum is correct, you should change this part to 1210 because 0805 is very rare for this component, can't get this for cheap money. Last edited by katarakt; 23 July 2017 at 19:55. Reason: added 3.

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03 July 2017, 07:56	#82
Jope - Join Date: Jul 2003 Location: Helsinki / Finland Age: 43 Posts: 9,861	Great stuff :-)

06 July 2017, 15:55	#85
Jope - Join Date: Jul 2003 Location: Helsinki / Finland Age: 43 Posts: 9,861	I doubt there is anything that would really need more than 512k of Slow RAM, but then again if you can expand it as far as possible with the minimum of effort, why not. :-)

06 July 2017, 16:22	#86
demolition Unregistered User Join Date: Sep 2012 Location: Copenhagen / DK Age: 43 Posts: 4,190	Yes, 1MB chip+1.8MB slow+8MB fast is better than 1MB chip+0.5MB slow+8MB fast. If the computer has fast mem, this will always be used ahead of slow mem since it has higher priority when talking OS friendly stuff. I don't know if maybe Action Replay can take advantage of using the upper slow mem since a game is very unlikely to utilize this?

06 July 2017, 16:41	#87
Mick Registered User Join Date: Jan 2004 Location: Yorkshire Posts: 710	I see, I suppose as well then it was useful for A500 owners in the days when fast memory was super expensive. I used to have a 500+ with 2MB chip so the whole fast/slow memory thing mostly passed me by.

10 July 2017, 01:41	#89
emiespo Registered User Join Date: Jul 2017 Location: Oxford Posts: 104	Hi there, This project is awesome, I would buy the 1meg version, but first I have one question: would a version with 2meg fast + adapter + 1 meg chip work in A500+ with an A590 board with 2 megabytes installed? Or the other FAST RAM would have an address collision? My goal is to have a WHDLoad box as close as the "original thing" as possible, thanks! :-)

10 July 2017, 08:18	#90
Jope - Join Date: Jul 2003 Location: Helsinki / Finland Age: 43 Posts: 9,861	The trapdoor Fast RAM is in a different part of the address space, so it would work ok together with the 590.

10 July 2017, 13:12	#92
Jope - Join Date: Jul 2003 Location: Helsinki / Finland Age: 43 Posts: 9,861	Ah, didn't think it through. Yet another gary board needed. ;-)

21 July 2017, 13:31	#95
katarakt Registered User Join Date: Jul 2017 Location: Germany Posts: 205	Thanks for reply. Yes 8 rams per 16MB-simm (front 4, back 4 = total 8), so each ram should be 2MB ...is this 1X32 ? Are you sure they will work? ...i first thought i bought the wrong simms. I've only checked that they have 21 pins (42).

24 July 2017, 19:40	#99
katarakt Registered User Join Date: Jul 2017 Location: Germany Posts: 205	Ok, thanks PeteAU It's totally still confusing because BOM #61 and BOM RTC#14 are different to some eagle layout infos. In eagle sch layout there says C11 is tantal (without value) and C12 is 100nf and RTC info #14 says tantal C12 ??? Would be great if you can give us a corrected detailed BOM, what means "* Lots of 100nF 0805 X7R capacitors" ?....can i use everywehre 100nf except the ones you wrote in parts list for RTC? I'm still confused ....so here is the not correct old complete "BOM" from #14 and #61: * Lots of 100nF 0805 X7R capacitors For 512K: * 1 x 1Mx16bit SOJ42 DRAM * 1 x 56pin (2x28) 2.54mm double row right-angle header (or 2x40pin and cut it) For A500+ 1MB: * one more DRAM For Gary Adapter: * more DRAMs (any number you want) * 1 x 74F139 (surface mount) (or maybe 74LS139 is fast enough) * 2 x 74F00 (surface mount) (or maybe 74LS00 is fast enough) * 3 x 3-pin jumper headers * 3 x jumpers * 2 x 24-pin DIP sockets * 2 x round pin strips * Wires and some 2 and 3-pin 2.54mm connectors of your choice (see my photos from previous page). The parts list for RTC: U4: OKI M6242B (I got some second hand ones from AliExpress for $2) Y1: 32.768KHz MC306 crystal C10: 100K 0805 resistor C13: 100nF 0805 capacitor C12: 4.7uF 10V 0805 tantalum capacitor R1, R2, R3: 10K 0805 resistor R4, R5: 330-470 0805 resistor D1: BAT721C or BAT54C diode C14,C15: 22pF 0805 capacitor Battery Holder: Some cheap ebay one. Alternatively, get a RTC-62421/72421 and you can leave off Y1, C14, C15. It makes it simpler.

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