RAM upgrade

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GregganG
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RAM upgrade

Postby GregganG » Sat Nov 10, 2018 11:24 am

Hey guys!
So I jumped on the ST train in the middle of the 80's but went over to PC's in the early 90's (when the 486dx2-66 was introduced) and been saving the ST in the attic since then - but I've brought it down couple of times for nostalgia.
Last time I noticed the internal drive of my 1040STfm was bad, making weird mechanical noises and just chewing on the floppies so I've now replaced it with a PC drive and it works fine, also checked all electrolyctics and besides the floppy it's in great working condition.. but I might also plan some other upgrades while I have it apart, like getting a 16MHz mc68k - memory upgrade - and some form of solid state/harddrive.

I have the 8-chip dram version http://rfelektronik.se/temp/atari/IMG_2 ... 171249.jpg
and found a couple of 8-chip 4MB ram sticks laying around http://rfelektronik.se/temp/atari/2018- ... .36.15.jpg
Looking at the datasheets the pinout is the same:
http://rfelektronik.se/temp/atari/D424256_NEC.pdf
http://rfelektronik.se/temp/atari/hm514400cltt-7.pdf
except for the A9 signal not in use on the smaller chips.
From what I gather the ST can adress 4MB of ram, however I read some games won't work with 4MB so I need to install a switch on the A9 either grounding it or enabling it, but the memory upgrade paper I saw used a single 4MB stick but how do I this with 8 chips soldered on the pcb - do I need to put the switch on A9 from the MMU? Which pin would be A9 on my 68pin MMU? http://rfelektronik.se/temp/atari/IMG_2 ... 204338.jpg

Or would it be possible to populate just 4 of the pcb slots? I would be happy with just 2Meg and would that get around the buggy games not working?
Just to get a little bit of ram disk...

Also are there any flashcard/harddrive interface designs worth making? I'm not looking to spend $100 on those commercial ones and I'm no stranger to making pcbs and programming micros myself.

Cheers!
//Greg.

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Greenious
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Re: RAM upgrade

Postby Greenious » Sat Nov 10, 2018 12:23 pm

It's not a huge problem with software not working with 4mb RAM, and more or less all got patched versions floating around. There's also a special boot disk somewhere that reconfigure your ram size temporary that also works well.

As for ram upgrade, probably the easiest is to use a 72 pin 4mb simm.

The simplest HDD design is probably adding an IDE interface, and using a cheap flash/SD to IDE adapter. Works best with TOS 2.06 though.

I recommend you to browse http://atari4ever.free.fr/ there you will find many inspiring DIY projects, such as ram upgrades and IDE.
Updated my guides as of june 28th, 2016. Check'em out and feedback!
viewtopic.php?t=5040

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Arne
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Re: RAM upgrade

Postby Arne » Sat Nov 10, 2018 12:43 pm

The 8chip (8pcs 514256 SMD) mainboard is probably the easiest to upgrade. I've done it with one of my 1040STFM and if you have access to a hot air station (for unsoldering) and you know what you are doing then I do not recommend the 4MB SIMM solution as it needs much wiring. Replacing the 514256 with 514400 needs just one wire (A9) and a ~68R resistor. But you have to solder one end directly to the MMU as it is not socketed on your board (neither on mine). But with a fine tip on your soldering iron it's no problem for a pro.
Better check the PS/2 SIMMs before unsoldering the ICs.

A9 is located on pin 64 of the MMU.

I suggest to populate bank #1 first (the one with /RAS0, /CASL0 and /CASH0 - pins 8,9 and 10 respectively) and check if it boots with this one. Then proceed with bank #2 (the one with /RAS1, /CASL1 and /CASH1 - pins 18, 21and 22 respectively).

You may get the schematics at my homepage.
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GregganG
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Re: RAM upgrade

Postby GregganG » Sat Nov 10, 2018 2:11 pm

Thanks for both replies!

I'm a analoge/RF engineer so I got all the tools and experience soldering, I do however I lack a lot in the area of adressing memory, do I bend out the A9 legs of the 514400's - wire them all to a 68 resisor soldered to the MMU pin 64? I'm not sure how the chip selecting works on DRAM...
Cheers

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Arne
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Re: RAM upgrade

Postby Arne » Sat Nov 10, 2018 3:40 pm

GregganG wrote:I'm a analoge/RF engineer so I got all the tools and experience soldering,

At least someone with knowledge finally :D
GregganG wrote:I do however I lack a lot in the area of adressing memory, do I bend out the A9 legs of the 514400's - wire them all to a 68 resisor soldered to the MMU pin 64? I'm not sure how the chip selecting works on DRAM...
Cheers

No bending. Neither the A9 pads on the PCB for the DRAMs nor the MAD9 pad beneath the MMU is connected to anything.
Just wire all A9 pins of the DRAM together, route it through a 68R resistor and then connect the resistor's other end to MAD9 of the MMU.

But start with 4 DRAMs on bank #1 first and check if the system boots again.

Good luck!
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GregganG
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Re: RAM upgrade

Postby GregganG » Sat Nov 10, 2018 4:24 pm

Thank you so much Arne!
All memory upgrade mods och ST schematics I found were either SIMM or the 16 DRAM versions and not for the 8 DRAM ones...
I'll give it a try, then test it with YAART.
I think I'll also add that hardware 4MB-1MB switch while I'm at it, by freefloating A9 from the MMU and grounding the A9 side of the DRAM - from what I gather is the correct way...

Thanks!

GregganG
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Re: RAM upgrade

Postby GregganG » Sun Nov 11, 2018 1:47 pm

Allrighty then, so I soldered in the new chips - pulled the wires from A9 to MAD9 via 68R

2018-11-11 00.06.21.jpg


Very nervously powering on - and it works!
Well - somewhat at least :) It only seems to see 2Meg, or actually it appears to see 4Meg but only use 2Meg according to sysinfo...
"Total ST-RAM 4096" "Free ST-RAM 1801"

IMG_20181111_135844.jpg


(here I had TOS 2.06 software loaded to see if it differed from original tos so it's a bit less)
I don't know why only 2meg is available booting from a clean floppy, electrically every dram pin connection is fine...

I also upgraded from TOS 1.02SE to 1.04SE, but all eproms I had was 27c512 instead of 27c256 so I had to cut the extra address pin (pin 1) and tie it to gnd.
Took some digging to find in which order to put the U2-U7 proms on my motherboard which has the proms labeled U48-U67 but it worked out in the end...
And I recapped the PSU (I read about those nasty DMA errors bad psu caps can make).

So it's been a productive day :)
Next up is trying to fit the PC floppy inside the chassis, and possibly trying to find some sort of flash/hdd solution.

Thank you so much for your help, really appreciate it!
Cheers!

//Greg.
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Arne
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Re: RAM upgrade

Postby Arne » Sun Nov 11, 2018 6:37 pm

GregganG wrote:It only seems to see 2Meg, or actually it appears to see 4Meg but only use 2Meg according to sysinfo...
"Total ST-RAM 4096" "Free ST-RAM 1801"


Never had that on a 4MB machine. There are two RAM tests built in TOS. The first just checks how many banks are available and what their sizes are. This one sets $F80001/$424 (seen in SysInfo). The more thorough test checks the "real" size. This makes the 3MB solution possible. So my guess here is that 1st test determined two 2MB banks and the second test failed very early in the second bank.
So better check the wiring of the second bank - anyway: professional wiring. :cheers:
Did you test that the SIMM was working properly before unsoldering the DRAMs?
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czietz
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Re: RAM upgrade

Postby czietz » Sun Nov 11, 2018 6:53 pm

Suggestion: When using YAARTTT.TOS (not(!) YAART.TOS as you would usually do on an ST) you select a "hidden" option by pressing "M" at the prompt. That way you can test address ranges that are not recognized by TOS. In this case, if you enter the range from 0x200000 to 0x3FFFFF you can test the second RAM bank and see which bit (=which chip) maybe causes the problem.

GregganG
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Re: RAM upgrade

Postby GregganG » Sun Nov 11, 2018 8:21 pm

Found a solderpad I had missed so .. my bad :) Now I got 4meg!

Attached a longer floppy cable and cut off the tab for the eject button and mounted the chassis back,
everything is working great and I thank you for your help, I should have done this years ago :)
All I need now is a flash/hard-drive and I'd be all set...

But for now I'm gonna dig up some Space Quest floppys and just enjoy that everything is working great!
Cheers!


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