joethezombie
Well-known member
Cooked up some 16MB SIMMs for the IIfx today based on Doug Brown's design! Worked perfectly! Thanks so much Doug! You're a legend! Needs more exalamation!!!
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IIfx 16MB SIMMs -- Thanks Doug!
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joethezombie
Well-known member
I ordered my boards through seeedstudio, because I had a pretty good coupon from a previous project. But ALLPCB will send you 20 boards for $56 which is still a bit cheaper than what I spent for mine. As far as chips, I spent $34.99 for a pair of 64MB modules on eBay, which had enough chips to make 9 completed SIMMs. All in all, a bit shy of $7 per SIMM. Not too shabby! I have two IIfxs to populate, and will need a couple more 64MB modules to complete the set, which will leave me with 2 spare SIMMs and 2 bare boards in case of a failure. So far, I've only built up the 4 shown, but they pass all memory tests I've tried.
I do feel bad for pillaging the chips from working modules. If I were to make a lot of these, I would certainly try to find a supplier of bare chips.
I do feel bad for pillaging the chips from working modules. If I were to make a lot of these, I would certainly try to find a supplier of bare chips.
joethezombie
Well-known member
Yeah, nothing in stock unfortunately. There is a seller on ebay with a whole reel of bare chips, but is listed as "away" for quite some time, and they never responded to inquiry. There is also the somewhat seedy asian distribution market, but with the few amount I was building, I didn't bother.
Juror22
Well-known member
I have access to some of these chips, TI TMS416400DJ - would these work? I checked out the spec sheets and the pins were almost the same between these and the ones listed as working:
M5M416100BJ
KM41C16000BK
There are some minor differences, but I'm not anywhere near fluent enough in reading these to tell if they are important minor differences.
By the way, those are some terrific boards - nice job!
M5M416100BJ
KM41C16000BK
There are some minor differences, but I'm not anywhere near fluent enough in reading these to tell if they are important minor differences.
By the way, those are some terrific boards - nice job!
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joethezombie
Well-known member
Indeed, trag's posts are what led me to your design so I have both of you to humbly thank! You guys are awesome!
@Juror22, I don't think those would work. They appear to be 4Mx4bit chips. Maybe they would work with trag's alternate 2-chip design that used a couple of bidirectional switches? Not sure.
@TimHD, I'm not planning on making anymore unless a bunch of raw chips happen to fall in my lap. It takes time to find the modules at a reasonable price on eBay, and even more time to remove them, and I don't have a lot of that.
But there is a gentleman over on mac68k.info that has secured a bunch of chips and has even boards. I'd been watching for him to make sets or even kits to sell, but after two years of waiting, and no response to private email, I figure it's not happening and made my own.
@Juror22, I don't think those would work. They appear to be 4Mx4bit chips. Maybe they would work with trag's alternate 2-chip design that used a couple of bidirectional switches? Not sure.
@TimHD, I'm not planning on making anymore unless a bunch of raw chips happen to fall in my lap. It takes time to find the modules at a reasonable price on eBay, and even more time to remove them, and I don't have a lot of that.
But there is a gentleman over on mac68k.info that has secured a bunch of chips and has even boards. I'd been watching for him to make sets or even kits to sell, but after two years of waiting, and no response to private email, I figure it's not happening and made my own.
joethezombie
Well-known member
5V 16Mx1
Mitsubishi M5M416100BJ
Samsung KM41C16000BK
There may be other compatibles:
http://jope.fi/conversionchart.htm#16dram
Mitsubishi M5M416100BJ
Samsung KM41C16000BK
There may be other compatibles:
http://jope.fi/conversionchart.htm#16dram
Bolle
Well-known member
Shouldn’t 16Mx4 work as well? You will only need two chips that way. I was thinking about getting a few 30-pinners done with chips from 64MB 72 pin SIMMs I don’t need anymore.
Those will also be low profile enough to fit well into SE/30s with only two chips.
Getting two 64MB SIMMs + having blank SIMMs manufactured cheaply will also cost less than buying 128MB worth of 30pin SIMMs from memorymasters and the like.
I might look into that. It was always tempting to max the RAM on my WGS95 }
Those will also be low profile enough to fit well into SE/30s with only two chips.
Getting two 64MB SIMMs + having blank SIMMs manufactured cheaply will also cost less than buying 128MB worth of 30pin SIMMs from memorymasters and the like.
I might look into that. It was always tempting to max the RAM on my WGS95 }
It'd be nice if 16Mx4 did work, even if such chips still aren't available via Mouser. And https://68kmla.org/forums/index.php?/topic/21519-finally-a-iifx/?p=221669 mentions a prototype involving paired 16Mx4s, a pair of FET bus switches (identified as SN74CBT3244 or similar), and a "five-pin gate" (probably an SN74xx1G series two-input of some sort)... But that they're finicky. Given the theory that the use of fewer chips is causing ringing on the address lines due to reduced load from the chips themselves, I was wondering if a set of fairly stiff pull-downs might help, but this is definitely beyond where I'd trust my intuition.
Hrm... 1Mx16 is available. That can be run as 2Mx8, since it has separate "upper" and "lower" CAS pins. Still 8 chips, plus glue, but if it can be made to work then sourcing components becomes straightforward.
Hrm... 1Mx16 is available. That can be run as 2Mx8, since it has separate "upper" and "lower" CAS pins. Still 8 chips, plus glue, but if it can be made to work then sourcing components becomes straightforward.
