Newly made 4MB 30pin SIMMs

Discussion about old PC hardware.

Newly made 4MB 30pin SIMMs

Postby Tiido » 2019-8-14 @ 23:12

SIMMs.jpg

After being frustrated with insanely high shipping costs and import taxes involved when trying to buy such RAM sticks from USA (where most of these can be bought it seems) I decided to make my own, of course plenty more got made than I need and the rest are up for grabs. If there's demand I will make more, it takes between 1 and 2 weeks to get new PCBs and chips.

These are 4MByte 60ns 30pin SIMMs, *without parity*, You will need to configure your board not to need parity for normal operation.
All of these sticks are tested at 40MHz bus speed with tightest timings on an OPTi 82C895 based board using Memtest86+ 4.10 to one flawless pass. Chips used are not NOS but there shouldn't be any sort of problems. 50MHz operation is not tested because I lack a 5V 50MHz bus speed capable CPU to test stuff with, only boards where I can run 50MHz FSB (using a 3.3V CPU) lack 30pin SIMM slots...
SIMMss.jpg


More materials around the creation of these things :
PCB design : http://www.tmeeco.eu/HARDWARE/30pinSIMM.png
First hand soldered test sticks : http://www.tmeeco.eu/HARDWARE/30pinSIMM0.jpg
They work :D http://www.tmeeco.eu/HARDWARE/30pinSIMM1.jpg
Paste + pick & place : http://www.tmeeco.eu/HARDWARE/30pinSIMM2.jpg
Cooking process : http://www.tmeeco.eu/HARDWARE/30pinSIMM3.jpg
My server is being a bit flaky due to a hardware issue (i'll sort it out soon), if an image won't load try again in a minute.

Official sale happens over AmiBay : http://www.amibay.com/showthread.php?107626-Newly-made-4MB-60ns-30pin-SIMMs.
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Re: Newly made 4MB 30pin SIMMs

Postby keropi » 2019-8-14 @ 23:50

these are nice :)

Image
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Re: Newly made 4MB 30pin SIMMs

Postby alvaro84 » 2019-8-15 @ 05:48

Tightest timings in OPTi895 at 40MHz? That's very nice, that's exactly what I went for (QDI OPTi895 + iDX4-100@120) when I decided to slim down my RAM pile - then quickly dropped the idea as very few could deliver this speed. Interesting that most 1MB sticks had no problems with it :confused: 72-pin sticks are usually fine with it too. 50-MHz operation is a totally different question, I've yet to find any 30 or 72-pin module that can do it at 3-2-2-2.
Shame on us, doomed from the start
May God have mercy on our dirty little hearts
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Re: Newly made 4MB 30pin SIMMs

Postby Grzyb » 2019-8-15 @ 09:46

keropi wrote:these are nice :)

Is that a 386SX... with fan???
Anyway, nice to see a CPU with its address space totally filled up.
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Re: Newly made 4MB 30pin SIMMs

Postby quicknick » 2019-8-15 @ 11:11

How hard would it be to add parity? Are the 4Mx1 chips hard to find?
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Re: Newly made 4MB 30pin SIMMs

Postby ph4nt0m » 2019-8-15 @ 12:59

quicknick wrote:How hard would it be to add parity? Are the 4Mx1 chips hard to find?

You can disassemble one 4Mb 30-pin SIMM consisting of 8 (9) 4Mx1 chips.
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Re: Newly made 4MB 30pin SIMMs

Postby SirNickity » 2019-8-15 @ 19:39

Nicely done! That is awesome. If the current PCB doesn't support optional parity, it would be nice to see a revision with the footprints available...
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Re: Newly made 4MB 30pin SIMMs

Postby Tiido » 2019-8-15 @ 19:53

You can see that there is a spot for parity chip and it'll work if you solder in the chip, I just don't have the chips for it (they're not very easy to get, and in particular 60ns), nor I find it to be any sort of necessity so there's none on these sticks.
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Re: Newly made 4MB 30pin SIMMs

Postby keropi » 2019-8-15 @ 20:06

Grzyb wrote:
keropi wrote:these are nice :)

Is that a 386SX... with fan???
Anyway, nice to see a CPU with its address space totally filled up.


it's the 486slc33 amstrad mobo that is compatible with the megapc - that's why there is a fan+heatsink :blush:
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Re: Newly made 4MB 30pin SIMMs

Postby rmay635703 » 2019-8-15 @ 20:30

Tiido wrote:You can see that there is a spot for parity chip and it'll work if you solder in the chip, I just don't have the chips for it (they're not very easy to get, and in particular 60ns), nor I find it to be any sort of necessity so there's none on these sticks.


Albeit wasteful a parity chip is just a 1 bit memory chip, would there be a way to only record single bits to a normal width memory chip?

Also some of my boards can take a 16mb 30pin simm,
Any future plans :0
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Re: Newly made 4MB 30pin SIMMs

Postby SpectriaForce » 2019-8-15 @ 21:34

That's an awesome project.

How long does it take for you to solder a set of 4 modules? You must be a pro in soldering and have the right tools :wink:

Do you also recap motherboards for others?
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Re: Newly made 4MB 30pin SIMMs

Postby Tiido » 2019-8-15 @ 21:53

The parity chip has data in and out as separate pins, while many motherboards connect them straight together on the SIMM connector allowing a normal chip to work, some might not and that makes in not possible to use normal chips for the parity. I imagine those boards that absolutely need parity are the latter kind so the right type of chip is necessary.

I have thought of 16MB ones but it wouldn't be done in any quantity since expense is great and usefulness is limited and right now I really need the dollars to buy firewood for the winter. I have no actual dayjob so hopefully these sticks will cover that expense ~

These are all made with reflow method, it took me couple hours to prep all the boards with paste and parts and roughly 40 minutes to cook them and 15 minutes per 4 sticks to test. Testing was the main time consumer and something that is absolutely necessary. A few boards had a soldering defect and got fixed up and those I kept for myself, the ones sold are all pristine looking.

I have repaired and recapped various things for a few people here.
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Re: Newly made 4MB 30pin SIMMs

Postby amadeus777999 » 2019-8-16 @ 08:51

Awesome!
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Re: Newly made 4MB 30pin SIMMs

Postby aljares » 2019-8-16 @ 09:36

fantastic :)
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Re: Newly made 4MB 30pin SIMMs

Postby imi » 2019-8-16 @ 10:43

awesome :)
I might get some maybe, the problem is I already have some ^^
... just one question, and excuse my ignorance, what is the main use for these, do pre-386 even benefit from ram faster than 70ns?
I'm asking because the 386 baord I'm planning to use right now already has 72-pin slots.
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Re: Newly made 4MB 30pin SIMMs

Postby ph4nt0m » 2019-8-16 @ 11:46

imi wrote:awesome :)
I might get some maybe, the problem is I already have some ^^
... just one question, and excuse my ignorance, what is the main use for these, do pre-386 even benefit from ram faster than 70ns?
I'm asking because the 386 baord I'm planning to use right now already has 72-pin slots.

Those 386 boards with 72-pin slots were made by IBM usually. They pioneered this module type while most other vendors were just fine with 30-pin SIMMs / SIPPs or even DIP chips.

70ns DRAM is good enough up to 50MHz and sometimes even 66MHz, but 60ns allows for better timings and compatibility. Although most people use such 30-pin SIMMs for up to 40MHz, so 60ns vs. 70ns doesn't really matter there. It is asynchronous DRAM, not synchronised to the system or memory bus, so you cannot overclock it the usual way.
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Re: Newly made 4MB 30pin SIMMs

Postby rmay635703 » 2019-8-16 @ 17:11

imi wrote:awesome :)
... just one question, and excuse my ignorance, what is the main use for these, do pre-386 even benefit from ram faster than 70ns?.


If you read computer magazines between 1989-1992
some manufacturers would advertise their systems with
Ram lower than 60ns sometimes coupled with the words ZERO wait state.
I have seen random speeds as low as 40ns

70ns ram is really only good to 16mhz but can under certain circumstances run synchronized up to 25mhz

So yes faster ram is useful in most any Pc if the system can support faster dram timings
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Re: Newly made 4MB 30pin SIMMs

Postby Tiido » 2019-8-16 @ 21:42

imi wrote:awesome :)
I might get some maybe, the problem is I already have some ^^
... just one question, and excuse my ignorance, what is the main use for these, do pre-386 even benefit from ram faster than 70ns?
I'm asking because the 386 baord I'm planning to use right now already has 72-pin slots.

If you have 72pin slots then you can easily get 60ns FPM sticks for it and should use them instead, it'll cost way less that way.
Stuff like a 286 is probably not going to benefit unless you overclock. I have one 286 that runs with 70ns sticks at 16MHz but will not POST when I overclock it to 20MHz, but with 60ns it will POST and run fine. My 386 board is going to benefit from the extra speed once I start playing with speeds higher that 40MHz. it comes down to what sort of timing settings a particular motherboard offers, 486 tend to have much finger grained options than anything before and substantial performance gains can be had.
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Re: Newly made 4MB 30pin SIMMs

Postby root42 » 2019-8-16 @ 21:51

Tiido wrote:I have thought of 16MB ones but it wouldn't be done in any quantity since expense is great and usefulness is limited and right now I really need the dollars to buy firewood for the winter. I have no actual dayjob so hopefully these sticks will cover that expense ~


Dude, if it's that hard for you, I bet some Vogons will gladly chip in to buy you a cubic meter or two of wood. Do you have a KoFi page or something to sponsor you? Would be worthwhile, maybe...
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Re: Newly made 4MB 30pin SIMMs

Postby Tiido » 2019-8-16 @ 21:56

I don't like to just ask for money, I do have a donation link on my sound card project page and there have been a few people who have donated and I'm very grateful to them ~
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