Reverse Engineering the Macintosh SE PCB & Custom Chips for 1:1 reproduction

[maceffects]

@ScutBoy thank you so much for your help!  I’m happy to pay whatever the charge was. I’ll start work on the PDS first as I think that will be easiest. Meanwhile, I’m probing around China to see if someone is skilled enough to reverse engineer the BBU reasonably cheap.  I also found a nice stock of 16mhz 68000 processors which should serve nicely.  Taking this side project wasn’t really a goal of mine, however, now I see it as a challenge that must be overcome. How cool would it be to have brand new SE boards with all new parts?  

 

[quorten]

It really isn't hard to adapt the original BBU design to support a 16 MHz CPU.  I'd guess the purpose of the drivers is primarily to support a soft switch for "turbo" in case you want to run at the normal speed.  I must admit that the back side of that PDS circuit board is quite funny looking, though.

@Kai Robinson @maceffects If you looked at the Unitron's PAL equations closely, reverse engineering non-registered PALs is not as easy as you'd think.  There's nothing that prevents a PAL equation designer from referencing the same output in its input equations, and in fact Burrell's design explicitly uses self-referrential equations to achieve some desired state machine effects with the non-registered PALs, thereby turning them into "registered" PALs.

Also, keep in mind that the BBU naturally doesn't provide as many "test points" as the Macintosh Plus cluster of PALs does.  If I should mention it again, it would have been a good idea to obtain a more comprehensive understanding of the Macintosh Plus before going for the Macintosh SE, but well, we have what we have.

EDIT: Brainstorm accelerated Macintosh Plus too:

https://lowendmac.com/2000/mac-plus-with-16-mhz-brainstorm-upgrade-benchmarked/

 

[ScutBoy]

AF had some drivers here, but the link seems to be broken now.

As best I could find when I was researching to refurb this machine, there are no "drivers" necessary for the Brainstorm. There was a firmware upgrade that I applied (1.0 -> 2.5) but there's nothing in the System Folder I could find, nor did an Internet search turn up any mention of drivers or Control Panels/Extensions. It seems to "just work"

Speedometer tests showed it as performing at approx 2X a Mac Classic.

There was also a Mac Plus version of the Brainstorm. I think that was one of the Killy Clip style of accelerators. Not sure if it replaced ROMs or anything like that.

 

[ScutBoy]

  I suspect the PDS card is also part of the system but that (should) be easy to do unless it has PAL in which case I'd have to send those out for to be reverse engineered. 

Yes - the PDS card is part of the Brainstorm system. You need both the PDS card and the BBU chip as far as I know.

 

[ScutBoy]

Info from Macworld back in the day:

Sometimes, the less said about a product, the better. In the case of the Brainstorm Accelerator for the Macintosh SE, that's praise. This upgrade does precisely what it should: make your SE faster and otherwise remain invisible. In this day of the Power Mac, accelerating an SE might seem absurd. Yet many SEs still lead serviceable lives in schools, homes, nonprofit organizations, and small offices, for which acceleration may be more practical than replacement.

The Brainstorm consists of an accelerator card that fits into the SE's expansion slot, and a Brainstorm Bus Accelerator (BBA) chip. The card contains a 16MHz 68000 processor—twice the speed of the SE's stock 8MHz 68000.

The unique part of the Brainstorm package is the BBA. It replaces the SE's 8MHz bus controller with a proprietary 16MHz chip, increasing the speed with which data shuttles between memory and SCSI peripherals (such as hard drives) on one side, and the processor on the other. The result is an SE that approaches a Classic II in overall performance.

  — Macworld (March 1995)

 

[Phipli]

https://macintoshgarden.org/apps/brainstorm-accelerator

I read older firmware versions needed drivers, but later ones didn't I think.

 

[maceffects]

@Phipli this one has the 2.5 newest Firmware. So if I copy that it should be good. The PDS card looks really strange. I hope it’s though hole but it maybe well be SMD.  In any event I’m sure I can reverse engineer that part if anyone wants to tackle the BBU. 
 

@quorten I must admit when things are above my head and the whole BBU is above my head. I know that the Brainstorm BBU does more than 16mhz per the results online.  Implementing those things is very much beyond my ability. I’m an accountant that likes to pretend he’s an engineer  :lol:

@ScutBoy at your convenience can you post pictures of the PDS card both sides? I want to start order parts I need to make a clone.  That one should be easy enough for me to do (I hope).  
 

 

[demik]

@maceffects reversing a PAL is 'easy' if the PAL isn't registered!  Can use the PAL dumper PCB here and read it as a 27C020 and reverse it from the .bin file it produces. 

View attachment 39580

Thanks, that will be useful !

 

[Phipli]

So could the contents of the Brainstorm be extracted from the firmware updater?

 

[ScutBoy]

So could the contents of the Brainstorm be extracted from the firmware updater?

Don't know, but the updater is on Macintosh Garden (along with previous versions) if you want to download it and play around

 

[Kai Robinson]

@asicsolutions - hadn't seen you for a few pages and it's starting to encroach on ASIC stuff again! Would you be up for helping the BBU reverse engineering?

 

[asicsolutions]

@asicsolutions - hadn't seen you for a few pages and it's starting to encroach on ASIC stuff again! Would you be up for helping the BBU reverse engineering?

Always. I think @maceffectswas making a breakout board. If I can get a hold of an SE with the breakout board I can ressurect my HP logic analyzer. I'm also open to other ideas on how to figure out what is going on.

 

[techknight]

what about decapping a stock BBU. using fuming nitric acid, and doing some type of die imagry/scan? 

 

[maceffects]

what about decapping a stock BBU. using fuming nitric acid, and doing some type of die imagry/scan? 

This can definitely be done but if I'm not mistaken it will need a scanning electron microscope and then someone to decode what is found.  I work at part-time at a university and they don't even let me near the good toys like that...  Though if anyone has access and knowledge to do so, that would be the most efficient way to do this.  Having a service do all of that could easily cost $10,000+.  For my accelerator idea, its not worth it and I don't think the combined effort for the new logic board is worth it.  But then again, if we know all of the logic on the board I don't see why a modern board using modern parts couldn't be made. 

@Kai Robinson that's right, I've ordered the 4 layer PCB from China and parts.  However, I realized this attaches to the PLCC on the logic board, right?  If so, I'm not sure I quite understand the entire design.  I get that the 84pin PLCC is on top with the BBU attached, but what about the one for the logic board, is there an adapter?  Can you send a photo of a completed unit?  Or maybe a part number for that.  I'll de-solder the PLCC from an SE board and attach the break-out and send it to @asicsolutions.  I don't really want to burden him too much on this project as I know he is busy and also is focusing much effort on the Xceed project.  While I think this might help a bit with this project, if it looks like it will take too much time, I'll see who I can dig up in China to help. 

 

[maceffects]

@techknight here is a cheap service in China: https://dirtypcbs.com/store/decap

But, if I'm not mistaken, if we can't see the gates it doesn't serve much purpose. 

 

[techknight]

@techknight here is a cheap service in China: https://dirtypcbs.com/store/decap

But, if I'm not mistaken, if we can't see the gates it doesn't serve much purpose. 

that was the idea of decapping and high resolution scans, for the potential of reverse engineering the gate structures. But, it would take someone in the semiconductor reverse engineering sector to know how to do this. 

 

[maceffects]

I'll ask around, it may be that I can find someone to do one or the other, but not both given that we aren't prepared to pay thousands.  That said, I'd even be willing to send a stock BBU for medium resultion pictures.  I'm not prepared to lose the Brainstorm for a crap decapping.  I'll ask one company how high of a resultion they can produce and at what given cost.  Maybe a medium resolution, @Kai Robinson's SE logic board schematic, and @asicsolutions's logic probe of the breakout can allow us to glean some of her secrets. 

 

[techknight]

but not both given that we aren't prepared to pay thousands.  

Yeaaahh.... thats kind of what I was afraid of. 

 

[Kai Robinson]

@maceffects, @techknight Actually...no need to pay thousands - friend of mine on discord is doing this with a desktop microscope and a raspberry pi4 w/HD camera module: https://chips.c128.se/8521R0/index.html

He's offered to decap and do die shots

Basically - if someone can get some DEAD custom chips - ie, ones with legs missing from battery damage etc - he can decap those, to spare working chips from being sacrificed. 

 

[maceffects]

@Kai Robinson I have a friend who has a good one in their battery damaged logic board.  Are you sure a digital microscope will get the gates?  In any case, PM me where to send this one to decap and do die shots.  Unless, anyone has a dead one, which I've never seen.  I'd assume it would be similar to the BBU from Brainstorm.