ITXPlus: A ITX Sized Macintosh Plus Logicboard Reproduction
- Thread starter max1zzz
- Start date
Torbar
Well-known member
This is an awesome project and definitely interested in either buying a kit or ordering the PCBs once its done
Thinking out loud here, I wonder how feasible another one with ADB ports would be?
A little slow? Hahaha, are you kidding me?! It feels like you've been working 24/7! Amazing job! I bet we'll see all sorts of mods adding or integrating more features based on your design. Just imagine, a version with a 68020 or 68030 CPU, an expansion slot (PDS?), ROM hacking to allow booting from larger OS images, a laptop version, etc.!I have been a little slow updating this thread but testing and tweaking has continued in the background, I'll do a full write up over the weekend but I'll leave this photo here in the meantime;
View attachment 86157
7.1 Boots from SCSI just fine
Snial
Well-known member
Excellent! I guess that the RAM chips will be 512K x 4-bit ones, because there's only 8?Revised boards have been sent off to JLC
Now featured on Hackaday!
A New Mac Plus Motherboard, No Special Chips Required
The Macintosh Plus was Apple’s third version on the all-in-one Mac, and for its time it was a veritable powerhouse. If you don’t have one here in 2025 there are a variety of ways to emu…
They are 1Mx4 ones, essentially the equivalent of 4 2 chip simms, I do also have some 1M x 16 chips on order to experiment with as it would allow just two chips to be used
Snial
Well-known member
My bad, I can't do simple multiplications! I guess they're old chips, because I assume no-one makes them any more? How much smaller is the board than an original Mac Plus logic board?
Last edited:
I'm not quite following? 8 1M x 4 bit chips makes 4MB
Snial
Well-known member
Hey, hey, I still had time to edit the comment
!Hey, hey, I still had time to edit the comment
I was only slightly doubting my own maths there Off the top of my head I think it's about 2/3rds the size in both dimensions but I'll double check that later
It should work with any 16 Mbits FPM RAM x 16 bits ICs ; no additional mux chips are required. Simply rewire inputs to the MUXs that generate RA0, RA1, RA8, and RA9 to meet 1024 refresh cycles, as @Golden Potato proposes here: 4MB memory upgrade development #122, and that's it. EDO RAM can be used also, but it will need to add a 7408
Last edited:
Snial
Well-known member
Could the same 4MB memory upgrade board work on an LC / LC II?
No, it couldn't. However, if you are referring to replacing the 2MB of onboard RAM, which is composed of 4-bit RAM ICs (HM514400A) on the LC, with just one 2MB 16-bit RAM chip like those used in Golden Potato's design, then yes, it could probably be done with certain handling of the CAS signals. This would require designing a specific carrier board that can tap into the RAM address and data buses, as well as the control signals. Why would you do that? Perhaps due to some irreparable damage to that section of the logic board, or because those 4-bit RAM ICs are too hard to find these days?
As far as I am aware no one makes FPM (or EDO) ram new so it's NOS or reclaimed - it's one of the reasons I went with 1Mx4's to begin with, it's very easy to find simms that the chips can be "borrowed" from
Tashtari
PIC Whisperer
Hmm. Is it possible to throw newly-available SRAM of some kind in there, or does it have to be DRAM?
An Octopart search for AS4C1M16E5-60JC shows it to be abundantly available brand new from several distributors. I bought mine on Aliexpress (brand new), but they can also be found on Amazon. Indeed, this chip could replace the onboard memory, thereby updating the LB replicas for the LC and Plus models. Could it be just leftover stock, perhaps?
AS4C1M16E5-60JC ALLIANCE Original supply, US $ 1.63-1.96 , Memory, [ALLIANCE] Alliance Semiconductor Corporation - SeekIC.com
AS4C1M16E5-60JC ALLIANCE, AS4C1M16E5-60JC Selling Leads, Price: 1.63-1.96 USD, MFG: [ALLIANCE] Alliance Semiconductor Corporation, Category: Memory, Summary: AS4C1M16E5-60JC, CMOS Dynamic Random Access Memory, -1.0V to 7.0V, 50mA, 1W, SOJ
kwlhk.en.seekic.com
BTW, this chip is the same used by Garrett’s Workshop in its 3MB RAM expansion board for the Classic.
Last edited:
Just a short late night post:
V1.1 boards have arrived and passed a basic power on test with no bodges
Only problem I had was nothing to do with the board, I brought a bunch of NOS DRAM IC's and about 1/3 of them seem to be bad. Had me hunting for assembly issues for a while before I just started swapping out RAM IC's which fixed the issue
V1.1 boards have arrived and passed a basic power on test with no bodges
Only problem I had was nothing to do with the board, I brought a bunch of NOS DRAM IC's and about 1/3 of them seem to be bad. Had me hunting for assembly issues for a while before I just started swapping out RAM IC's which fixed the issue
