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Macintosh SE EEPROM to ROM adapter

Posted by: Kai Robinson on 2020-12-20 09:36:48

So, you have a Mac SE, or you're building up a Mac SE reloaded board using damaged donor that might have bad ROM chips (corroded legs, dead chip etc).

Well through the magic of the internet I can bring you this, an adapter that replaces the stock Toshiba TC531000 mask ROMs with any 27C010's you choose, so you can customise the image if you want!

Test runs are printed in red, but available to anyone who wants one for cost of postage.

Production boards will be open source but I may sell a batch for those that don't want the hassle of making PCBs!

Posted by: BacioiuC on 2020-12-20 09:49:09

You're doing amazing work! As an SE owner, I thank you. Anyway to support you before production boards are done?

Posted by: Kai Robinson on 2020-12-20 10:07:36

@BacioiuC erm - i mean you can donate via PP if you really want - if you want a PCB for the EEPROM adapter, let me know, it's yours for the cost of postage - I have 8 spare - i did them as panels, so if you want 2, i'll send them on a sprue 🙂

Many Thanks, Kai

Posted by: BacioiuC on 2020-12-20 10:15:44

IIRC you're also doing a re-engineering of the SE right? Would like to donate for this and that since it's amazing work for long time vintage mac supports. I scanned the PCB Reverse Engineering thread a few times I don't remember seeing a paypal link, so this is why I brought up donation/supporting 🙂.

Would love a pcb. Would make a perfect gift for a friend who resurrects and refurbishes dead macs 🙂

Posted by: Kai Robinson on 2020-12-20 10:24:01

Theres no direct PP link as per forum decorum - but i can give it to you in DM, but don't feel obligated at all to support 🙂

Posted by: rickyzhang on 2020-12-28 13:19:48

Can you make the Mac SE ROM chip upgradable instead of write-once only?

I patched an emulator Basilisk II Mac SE ROM to extend new features. I’d love to tinker the 68K assembly for my physical Mac SE.

Posted by: Mu0n on 2021-01-01 13:29:13

I don't mean to be dense, I'm honestly curious, but first, here's where I'm coming from - 2 years ago, I noticed my best Mac Plus (platinum, 4 mb RAM) was no longer booting, so I recapped it and realized that the ROM was faulty, as I had another Mac Plus in working order, so a swap of the ROMs worked. I eventually equipped myself with the TL866 II plus everyone has, and not knowing all too much about EEPROM writing, I stumbled upon a batch of Winbond W27C512-45Z and tried it out after figuring the hi-lo split. It worked.

What is the exact advantage of the PCB you're doing here? The pinouts aren't the same? Meaning, I was extra lucky my EEPROM chips would work right away on the Plus?

Posted by: Kai Robinson on 2021-01-01 16:04:44

@Mu0n So the EEPROM's aren't the same pinout as the Mask ROM's the SE comes with - one address pin is in a different position. The 128k x 8 EEPROM's are 32-pin, but the Mask ROM's are 28-pin.

@rickyzhang Well, thats the beauty of using EEPROM's instead - as long as the image fits in 128KB in 64KB chunks (Low/High) - then i see no reason you can't do that.

Posted by: trag on 2021-01-02 11:38:54

What is the exact advantage of the PCB you're doing here? The pinouts aren't the same? Meaning, I was extra lucky my EEPROM chips would work right away on the Plus?

At the change from 512Kbits (64KB) and lower to 1 Mbit (128KB) and larger, several pins in the DIP package pinout moved. So it is not simple to substitute the larger capacity 1 Mbit chips for the 512Kbit chips, without using an adapter board such as this one.

Posted by: Kai Robinson on 2021-02-07 04:52:50

Re-done design, should make for a better fit. Just had a run of PCB's done at JLC - only cost £21 inc shipping DDP.

Here are the Gerbers, enjoy 🙂

View attachment TC531000 to 27C010 EEPROM Adapter.zip

Posted by: tontonmax63 on 2021-08-29 16:55:27

Hi,

It's very interesting.

but can you explain what is RN1 ?

Posted by: Daniël on 2021-08-30 04:13:48

but can you explain what is RN1 ?

A resistor network. I am not aware of the Ohm value of this particular one.

Posted by: tontonmax63 on 2021-08-30 04:55:03

maybe Kai Robinson have this information 😀

Posted by: olidlavoie on 2022-01-05 22:13:20

Any idea where to find Hi/Lo rom files, or how the rom is split? Can't find much info about this, alros did anyone ever find out the rnets value?

Posted by: dochilli on 2022-01-06 03:15:14

ROMs are here:

All Macintosh ROMs (68K + PPC) - Macintosh Repository

This is an archive containing all of the most popular Macintosh models ROM files for emulation purposes, ranging from the first 64K ROM from the...

www.macintoshrepository.org

Those files must be splitted into even and odd bytes.
My software (Windows) for splitting and comparing ROMs is attached.

Posted by: olidlavoie on 2022-01-13 08:28:16

Thank you so much! I was so close, i had tried splitting it with a program made for splitting TOS roms, and that did not work (i think it was splitting them differently), now i understand why... Guess i'll order more 27C010 chips hahah
The compare tool sees over 1000 differences with the high.rom from my previous tentative hahah

Posted by: Wulf Wulf on 2023-03-30 23:11:52

Hi all, please what is the value of RN1?

Posted by: Wulf Wulf on 2023-04-12 18:46:55

Hi all, please what is the value of RN1?

@Kai Robinson, can you inform what is the value of RN1 please? A part link to Mouser or Digi-key would be also great. Thanks.

Posted by: dochilli on 2023-04-14 02:30:45

I do not know, if it helps, but in this thread (last post) there is another adapter (for one 27C010):

Macintosh SE broken ROM LOW chip

Hi all, I have a Mac SE showing a barcode-like pattern: A friend of mine has the same computer, so we swapped parts until we found the culprit: the 342-0353-A (rom low) chip. I got the BIN image on the web (64 kB), but I don't know if I can use a 27c512 eprom as direct replacement or not; do...

forum.vcfed.org

There are two 4.7kOhm Resistors used to connect the 5V to VPP, PGM and OE.
I think that this is used in the same way in the above adapter.

Posted by: Phipli on 2023-04-14 02:35:41

@Kai Robinson, can you inform what is the value of RN1 please? A part link to Mouser or Digi-key would be also great. Thanks.

Try asking on Tinker Different, Kai hangs out over there these days.

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