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#81 |
Registered User
Join Date: Aug 2014
Location: Netherlands
Posts: 703
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New gary adapter board
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. |
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#82 |
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Join Date: Jul 2003
Location: Helsinki / Finland
Age: 44
Posts: 9,964
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Great stuff :-)
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#83 | |
Registered User
Join Date: Dec 2016
Location: Australia
Posts: 113
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Quote:
![]() 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+. |
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#84 |
Registered User
Join Date: Jan 2004
Location: Yorkshire
Posts: 774
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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. |
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#85 |
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Join Date: Jul 2003
Location: Helsinki / Finland
Age: 44
Posts: 9,964
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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. :-)
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#86 |
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Join Date: Sep 2012
Location: Copenhagen / DK
Age: 44
Posts: 4,190
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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? |
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#87 |
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Join Date: Jan 2004
Location: Yorkshire
Posts: 774
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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.
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#88 | |
Registered User
Join Date: Aug 2014
Location: Netherlands
Posts: 703
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Quote:
![]() Most fast RAM boards are way more complicated and also often need some CPLD's or GAL's programmed. |
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#89 |
Registered User
Join Date: Jul 2017
Location: Oxford
Posts: 107
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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! :-) |
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#90 |
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Join Date: Jul 2003
Location: Helsinki / Finland
Age: 44
Posts: 9,964
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The trapdoor Fast RAM is in a different part of the address space, so it would work ok together with the 590.
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#91 | |
Registered User
Join Date: Dec 2016
Location: Australia
Posts: 113
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Quote:
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#92 |
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Join Date: Jul 2003
Location: Helsinki / Finland
Age: 44
Posts: 9,964
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Ah, didn't think it through.
Yet another gary board needed. ;-) |
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#93 | |
Registered User
Join Date: Jul 2017
Location: Germany
Posts: 205
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Quote:
Last edited by katarakt; 30 December 2021 at 22:44. |
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#94 |
Registered User
Join Date: Dec 2016
Location: Australia
Posts: 113
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#95 |
Registered User
Join Date: Jul 2017
Location: Germany
Posts: 205
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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).
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#96 |
Registered User
Join Date: Dec 2016
Location: Australia
Posts: 113
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No, it's 1M x 16.
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. |
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#97 |
Registered User
Join Date: Jul 2017
Location: Germany
Posts: 205
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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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#98 | |
Registered User
Join Date: Dec 2016
Location: Australia
Posts: 113
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Quote:
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. |
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#99 |
Registered User
Join Date: Jul 2017
Location: Germany
Posts: 205
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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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#100 | |
Registered User
Join Date: Dec 2016
Location: Australia
Posts: 113
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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:
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