Great work! The next level would be to buy an IBM PS/2 Speech Adapter, 3D-print the (never-shipped) internal mounting bracket for the front panel of a Model 30, and re-wire it to use the 'official' speaker. 😀

Sweet build! I love everything IBM!

So total RAM became 12.5MB, as this expansion board requires "2 x 256KB only" on the motherboard.

Are you sure about that? I was under the impression it can fill the 4mb-16mb range. Also are those 12 simms "normal"?

Third, what's with that mod on the left VLSI chip in the 8th image

luckybob wrote:

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Sweet build! I love everything IBM!

So total RAM became 12.5MB, as this expansion board requires "2 x 256KB only" on the motherboard.

Are you sure about that? I was under the impression it can fill the 4mb-16mb range. Also are those 12 simms "normal"?

Third, what's with that mod on the left VLSI chip in the 8th image

Yes I'm sure.
I don't know why this is required.
It's stated in the manual and I tested it too.
The DIP siwtches select enable/disable serial/parallel ports, and the starting range of the memory (and whether you want to use some to top up base from 512KB to 640KB).
Starting address is any 0.5MB increment starting at 1MB.

The manual specifically states, to get a maximum of 15.5MB, you need two of these boards, with the second one filled with 256KB SIMMs to make 3MB.

=====

And no, this board is designed for this one system only, and only takes the PS/2 Type SIMMs, hence having to modify 12 of them.

=====

That mod to the VLSI chip is an undo to a previous mod to disable RAM waitstate. Was never stable, depsite the huge performance jump.
Also wasn't stable at 12MHz, even with a 16MHz rated 286, and the chipset being marked as 12MHz rated.

Well there are typically 2 reasons; "because fuck you thats why" and "some non-technical manager at IBM thought it was a 'good idea'. "

I have one, and 12x 512k simms for it. I only asked because your simms did not appear to be special.

that 0 WS mod sounds interesting. I'll have to look it up.

Any chance you want to mod like 16 more simms? I can't do it properly and you already have experience...

P.S.

I was under the impression the 3-chip ram isn't recommended for this mod for the model 30. maybe that was the real cause of the instability?

luckybob wrote:

P.S.

I was under the impression the 3-chip ram isn't recommended for this mod for the model 30. maybe that was the real cause of the instability?

The 3-chip RAM is fine for 256KB modules.
Not for 1MB ones; the chipset doesn't support this high density.
Now, one thing I'm not sure on is whether the RAM board supports 3-chip 1MB; it does have its own lil memory controller in that neat metal chip...

luckybob wrote:

Well there are typically 2 reasons; "because fuck you thats why" and "some non-technical manager at IBM thought it was a 'good […]
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Well there are typically 2 reasons; "because fuck you thats why" and "some non-technical manager at IBM thought it was a 'good idea'. "

I have one, and 12x 512k simms for it. I only asked because your simms did not appear to be special.

that 0 WS mod sounds interesting. I'll have to look it up.

Any chance you want to mod like 16 more simms? I can't do it properly and you already have experience...

Interesting. The manual says only 256KB and 1MB work in the expansion board.

The 0WS is unstable. I think it will be for everyone. Tried with many different RAMs including the chipset recommended 80ns.

I can make you 16. I need to source the right ones again.
Would be about $20 a pop if you bought that many. More if you wanted less.

I do have a bunch of leftover ones from various brands I could sell you for half price. They may or may not be stable together. I did not scientifically test. It may be due to some being dodgy, some being simply not compatible, or the board not liking you mixing different speeds and brands.

It now seems completely stable with 12 x identical SIEMENS 60ns modules.

One thing you didn't mention is that you replaced the CPU with a Harris 16MHz 286. Were you trying to do some overclocking?

Also, where are you guys getting those 12MB IBM RAM cards?

Anonymous Coward wrote:

One thing you didn't mention is that you replaced the CPU with a Harris 16MHz 286. Were you trying to do some overclocking?

Also, where are you guys getting those 12MB IBM RAM cards?

Yea that was for testing 12MHz, which wasn't stable enough.
I left it in there because it runs wayyyy cooler than the original Intel 80286 10MHz.

It's not a 12MB IBM RAM card, it's an empty RAM card, that is only for the PS/2 Model 30-286. I swear the seller on eBay had two, but looks like they're gone.
It only becomes a 12MB card when you can find 12 x 1MB PS/2 SIMMs. These are damn near unobtanium. I modified regular SIMMs.

it also works on the IBM AT. IIRC. I've had mine for a few years. got it cheap because some of the slots had broken retention clips.

one of the 100's of little projects i have.

I really hate those angled SIMM slots with the crappy plastic retention clips. They always break. Are there any replacements with metal clips out there?

If you see anymore of those IBM memory boards, please let me know.

Anonymous Coward wrote:

I really hate those angled SIMM slots with the crappy plastic retention clips. They always break. Are there any replacements with metal clips out there?

If you see anymore of those IBM memory boards, please let me know.

Hey, the same guy I got my Model 30-286 RAM board off has one left: https://www.ebay.com/itm/253592282420

Just to clarify again:
> This is for the Model 30-286 only. Not sure if it works with anything else.
> This only works with 2 x 256KB modules in slot 0 and 1 on the motherboard. No other motherboard memory combinations will work with the card.
> This takes 256KB or 1MB modules. You can install any number of pairs, but they must all be the same size.
> This needs PS/2 Type SIMMs, if that wasn't clear enough. Regular unmodified 30-pin parity SIMMs won't work.
> Be sure to set the jumper so that the onboard parallel and serial port are secondary ones.
> I encountered instability when using various brands and speeds (60ns, 70ns, 80ns) of modified 1MB SIMMs. It is not confirmed this was the issue, as I changed some other things between then and fixing it. But one of the things I changed was making every SIMM on the memory board the same modified 60ns SIEMENS ones.

Hope this helps!

qtaf
whats the plan here? are You gonna look for 20+mhz harris to have wolfenstein run well?
would You post a bench of Your memory and ethernet speeds?
how much of that mem do You even get to use and what with?
thought of upgrading vga?

mrau wrote:

qtaf whats the plan here? are You gonna look for 20+mhz harris to have wolfenstein run well? would You post a bench of Your memo […]
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qtaf
whats the plan here? are You gonna look for 20+mhz harris to have wolfenstein run well?
would You post a bench of Your memory and ethernet speeds?
how much of that mem do You even get to use and what with?
thought of upgrading vga?

Won't upgrade VGA coz that would use an ISA slot.

Ethernet speed is 220KB/s.

Memory speed is roughly 4MB/s in various benchmarks.
Memory speed is same on motherboard or on 16-bit ISA RAM card.

You can't even get to 12MHz in this system due to board instabilities, not CPU instability, so stock 10MHz is what it's at.
The Harris 16MHz chip that's installed runs much much cooler at 10MHz than the original Intel 10MHz chip.

nztdm wrote:

Hey, the same guy I got my Model 30-286 RAM board off has one left: https://www.ebay.com/itm/253592282420

I'd like to point out, if I had the cash, I would buy both IMMEDIATELY.

luckybob wrote:

I'd like to point out, if I had the cash, I would buy both IMMEDIATELY.

is this in any way better than a generic memory card?

quite the opposite. it is ONLY for the IBM model 25/30 and maybe 5160 (at 286)

nztdm wrote:

Ethernet speed is 220KB/s.

thats a weird number - more than half of what Treasons 486 did over vlb 😮

nztdm wrote:

Memory speed is roughly 4MB/s in various benchmarks.
Memory speed is same on motherboard or on 16-bit ISA RAM card.

that' s unexpected - you would think isa just has to slow things down

mrau wrote:

thats a weird number - more than half of what Treasons 486 did over vlb o.O […]
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nztdm wrote:

Ethernet speed is 220KB/s.

thats a weird number - more than half of what Treasons 486 did over vlb 😮

nztdm wrote:

Memory speed is roughly 4MB/s in various benchmarks.
Memory speed is same on motherboard or on 16-bit ISA RAM card.

that' s unexpected - you would think isa just has to slow things down

I suppose with a 286 system things are slow enough already, that the roughly 8MB/s of ISA isn't an issue.

And for Ethernet speed, these were tests for transferring files from my main PC using mTCP's FTP, and the Accton EN1661 Ethernet card with packet driver. It was pretty solid stuck on 220KB/s. The storage device is a CF card through the sound card's IDE interface and gets 1.2MB/s.