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

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

Post by Icky »

@Kai Robinson when placing images into posts please make sure you attach them and place in-line as opposed to linking to other sites. This way we can make sure the image still exists even if the external site disappears or has issues.

I have done the images in question for you in the post above - https://www.exxosforum.co.uk/forum/viewt ... 361#p56361 and here is a guide to adding and placing images. https://www.exxosforum.co.uk/forum/viewt ... =20&t=2357
Kai Robinson
Posts: 43
Joined: Wed Mar 13, 2019 12:01 am
Location: East Sussex

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

Post by Kai Robinson »

Icky wrote: Tue Jan 19, 2021 8:02 am @Kai Robinson when placing images into posts please make sure you attach them and place in-line as opposed to linking to other sites. This way we can make sure the image still exists even if the external site disappears or has issues.

I have done the images in question for you in the post above - https://www.exxosforum.co.uk/forum/viewt ... 361#p56361 and here is a guide to adding and placing images. https://www.exxosforum.co.uk/forum/viewt ... =20&t=2357
Noted for future reference :)

Despite un-bridging the A8 and /AS lines, i also discovered T0CKI on the ADB MCU (PIC16CR54 for reference), weren't connected to the ADB signal...as the ADB MCU is tied to the /RESET line as well, this might also be the cause of the wierd reset behaviour (reset loop of 124 cycles, over and over again). I've tested the BBU, the SWIM and ROM's in another machine, so at least i can rule out them as an issue, although i'm getting some very, very odd signals out of the 74F257's, so i've ordered some new ones from mouser in bulk, along with some new 74LS245's. I literally can't see any wierdness on the bus other than that, and some wierd 'ramping' of the signal on /AS...I'll post pics in a bit, if anyone fancies having a go at figuring out the issue!

I've verified the clock signals are all good, though, both the 3.73MHz peripheral clock and the 7.83MHz CPU clock - the GLU chip clone seems to work absolutely fine, too, which is great!
Kai Robinson
Posts: 43
Joined: Wed Mar 13, 2019 12:01 am
Location: East Sussex

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

Post by Kai Robinson »

Ooof - a lot has happened since i last posted, for the full story, the project over at 68k MLA will fill in the gaps - but essentially, a respin was needed, after that respin - we managed to get some helpers to look over the sprint layout, as my eyes weren't picking out anything - and 5 really important bugs were discovered, not least of which was a SCSI reset line issue, as well as the whole /AS to A8 bridging (DOH!)



Here's the YouTube playlist for the bringup of the v1.5 board - see for yourself how it turned out ;)
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