4Mb MMU Socket Upgrade questions

Upgrade your RAM from ST to Falcon.
polbit
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Re: 4Mb MMU Socket Upgrade questions

Post by polbit »

Well, after I disabled on-board memory with the resistors and attempted boot, the machine would show nothing, wouldn’t even seek floppy. I wanted to go back to known good state, so I removed the upgrade, and connected the resistors back. Now everything works, but I get thin, black, vertical lines every 1/3 inch or so (mono screen) They don’t move, are completely steady... Any ideas?
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Re: 4Mb MMU Socket Upgrade questions

Post by rubber_jonnie »

polbit wrote: Tue Aug 11, 2020 4:44 pm Well, after I disabled on-board memory with the resistors and attempted boot, the machine would show nothing, wouldn’t even seek floppy. I wanted to go back to known good state, so I removed the upgrade, and connected the resistors back. Now everything works, but I get thin, black, vertical lines every 1/3 inch or so (mono screen) They don’t move, are completely steady... Any ideas?
Which resistors did you pull up to 5v? Do you have a picture? Also, if you connect 5v to the the wrong side of the resistors, it won't work.

EDIT:

You need to pull up R59, R60 & R61 at the end furthest from the RAM and connect all 3 to 5v. If you currently have 1MB installed you need to do the same for R71, R72 & R73 as per the guide here: https://www.exxosforum.co.uk/atari/last/4MBMMU/index.htm
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Re: 4Mb MMU Socket Upgrade questions

Post by exxos »

You should probably run YAART You might have bad RAM or just video interference.
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Re: 4Mb MMU Socket Upgrade questions

Post by rubber_jonnie »

exxos wrote: Tue Aug 11, 2020 4:57 pm You should probably run YAART You might have bad RAM or just video interference.
My bet is interference.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
polbit
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Re: 4Mb MMU Socket Upgrade questions

Post by polbit »

exxos wrote: Tue Aug 11, 2020 4:57 pm You should probably run YAART You might have bad RAM or just video interference.
Ran two passes, RAM is OK.

Tried two shifters, reflowed all legs of the socket I had to install for it.

The only other change I’ve done is install a blitter socket (no blitter yet) but I did not open up the vias, so I don’t think that would impact it. The computer worked perfectly fine yesterday...
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Re: 4Mb MMU Socket Upgrade questions

Post by exxos »

Is your power supply recapped at least ? ... But I think you are drifting onto another topic here relating to video interference not RAM issues.
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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polbit
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Re: 4Mb MMU Socket Upgrade questions

Post by polbit »

exxos wrote: Tue Aug 11, 2020 5:40 pm Is your power supply recapped at least ? ... But I think you are drifting onto another topic here relating to video interference not RAM issues.
I am using a Mean Well RD-50A for PSU right now, and it works fine in my main 1040STF with 4Mb RAM.
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Re: 4Mb MMU Socket Upgrade questions

Post by exxos »

Well video issues you should open up a new topic and concentrate on the ram issue in this thread. But noise on the video is a inherent issue on most machines anyway, so its unlikely fixable.

Also as mentioned, please post a image of how you disabled the onboard ram.
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
polbit
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Re: 4Mb MMU Socket Upgrade questions

Post by polbit »

I just fixed a 520STF motherboard (replaced CPU), and want to attempt upgrading with the 4Mb kit again. With that said, can someone tell me exactly which 68R resistors do I need to lift and tie to 5V? This MB seems to have few extras...
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Re: 4Mb MMU Socket Upgrade questions

Post by exxos »

It will be the 68R ones..
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
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