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SE/30 VIA chip replacement

VIA of SE/30 is
338S6523 　(11484 -28, -30, -44 etc. ) = R65NC22J (Rockwell) VL65C22V-02QC (VLSI)

Model numbers are from multiple SE/30's on real machines.

I think the closest thing to R65NC22J is W65C22N6TPLG-14, not W65C22S6TPLG-14.
Please refer to P.32-35 and P.50 of the PDF.

A long time ago, I bought one listed as "R65NC22J4 (11484-39)" on Taobao and it worked fine.
 

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I will try the W65C22N6TPLG, it’s available on Mouser.

From the PDF you linked, it appears there are some minor design deviances regarding the port buffers.

I don’t think TaoBao is accessible to foreigners anymore, pity as some sellers currently have the R65NC22J4.
 
Last edited:
croissantking said:
I will try the W65C22N6TPLG, it’s available on Mouser.

From the PDF you linked, it appears there are some minor design deviances regarding the port buffers.

I don’t think TaoBao is accessible to foreigners anymore, pity as some sellers currently have the R65NC22J4.
Click to expand...
Did it work?
 
Hum. Just to warn you, the WDC part is not 100% compatible with older types. I forget the specifics, and the Mac might not use those features, but I know it isn't identical.
 
There is an 'N' and an 'S' version. You bought the one that is designed to replace NMOS parts, which is probably the right thing to do, hopefully it is happy replacing CMOS parts too.
 
So it does work.

I mean, it boots up and I can use the computer. Do I need to do any specific kind of tests?
 
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croissantking said:
So it does work.

I mean, it boots up and I can use the computer. Do I need to do any specific kind of tests?
Click to expand...
The first download here is for 68k :

MacTest Pro - Macintosh Garden

MacTest Pro is repair-oriented diagnostic software that can test logic boards, video cards, monitors, floppy drives, hard drives, and CD ROM drives. It can also detect software corruption problems, and the existence of multiple System Folders on a volume. MacTest Pro is intended for use by Apple...
macintoshgarden.org macintoshgarden.org

it will test logic board chips, but you have to specifically turn the VIA tests on from the setup button.
 
I’ve done a bit of testing. MacTest Pro is happy with the VIAs, and both sets of ADB and serial ports work fine. The internal floppy works too but I haven’t tried an external yet. No weirdness at all during about 2-3 hours’ use. Also just to mention that I tried the new VIA in both locations as my board is socketed.
 
croissantking said:
I’ve done a bit of testing. MacTest Pro is happy with the VIAs, and both sets of ADB and serial ports work fine. The internal floppy works too but I haven’t tried an external yet. No weirdness at all during about 2-3 hours’ use. Also just to mention that I tried the new VIA in both locations as my board is socketed.
Click to expand...
This all really confuses me.

While the silkscreen says 6522, Apple's documentation says the SE/30 uses a 6523, at least for one of the vias. The 6523 is a different thing, it has 3 ports instead of 2 and other differences... The one you replaced must be a 6522, so it must have one of each.

I need to sit down with some manuals and work out whats going on.

Which VIA did you replace? VIA1 or VIA2? Do you have photos / what are the silkscreen labels? Sorry for asking, you've got me curious!

Screenshot_20230709_125806_Drive.jpg
5th column is the SE/30 so... erm... eh?
 
OK, so I found the following. It seems what Apple call the 6523 isn't the same part I found elsewhere. Its some kind of custom 6522 part that they've made with a synchronised serial port (I2C if I remember) and some bug fixes (the 6522 was famous for having a couple of bugs that the whole industry had to work around).

If I remember, the WDC chip also fixes the main bug, but I'll have to remind myself of the specifics. That just leaves the behaviour of the I2C...

My question would be... does the clock work properly? Can you set the time (insofar as you normally can).

@Bolle do you know anything about the 6522 vs Apple's 6523 from your SE/30 projects?

Screenshot_20230711_100111_Drive.jpg
 
Some light reading for anybody interested...

The 6523 is the standard part fitted to the SE/30, the "VIA Cell" document describes the functionally similar cell that was baked in to other chips when Apple integrated the VIA in later machines. This document helpfully details where the new embedded cell differs from the previous 6523. Sadly I can't find a copy of Apple's spec 338s6503, which describes the 6523, but apparently the VIA Cell document is based on it.
 

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