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Mac Plus - Identify this Memory Expansion

Hi there,
First post to this forum. I was wondering if anybody can identify this memory expansion attached to my Macintosh Plus (Macintosh Plus 1Mb). It connects only to the first two SIMM slots on the logic board, and there is a small red jumper attached to two points on the logic board as well. R9 ( labeled "ONE ROW" in the RAM SIZE select area on the logic board does not look like it has ever been installed. Was this a factory addition? See the two images attached.

I am just rebuilding the Analog Board, so have not run the unit up to see what the OS says about RAM size as yet.

Thanks in advance.

20231009_115137.jpg

20231009_115120.jpg

20231009_115833.jpg
 

SuperSVGA

Well-known member
Looks like one of the 4MB max upgrade boards, maybe RamPlus 4 or something. Though I'm not sure, it looks like about 2MB there right now. Maybe it's the One Plus One.
 
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Phipli

Well-known member
It has four 256k SIMMs installed, plus a second 1MB soldered... With an additional 128k, but only 4bits ?? Weird. Are there chips on the other side?

I wonder if it is just an adapter to fit four SIMMs into two slots so you can reuse your stock RAM when upgrading? Except they're usually simpler than this, and this looks like it would cost more than the RAM. Is there any silkscreen name on the board?

Putting two 1MB SIMMs in the other two slots should give you 4MB, but with that card there, I'm not sure what you do with the RAM resistors.
 

cheesestraws

Well-known member
I don't know but that looks like an incredibly complicated way of adding memory to something with SIMM slots. I'm curious about what it is and why.
 

SuperSVGA

Well-known member
I don't know but that looks like an incredibly complicated way of adding memory to something with SIMM slots. I'm curious about what it is and why.
As I understand 1MB SIMMs or 1,048,576x1 bit DRAM was expensive or hard to get, so this allowed you to use 256KB SIMMs and also utilized 262,144x1 bit DRAM.
 

Phipli

Well-known member
As I understand 1MB SIMMs or 1,048,576x1 bit DRAM was expensive or hard to get, so this allowed you to use 256KB SIMMs and also utilized 262,144x1 bit DRAM.
Yeah, but there are way simpler ways of doing this. I have the equivalent for 72pin SIMMs upstairs, and have seen 32pin ones that are basically just a SIMM with a socket in the back.
 

demik

Well-known member
That's weird. The plus Itself can go up to 4MB, which is a ceiling for this machine (unless you go 68020+ upgrade)

It's either a way to workaround memory costs, or it does some trickery (there is two PALs) like :
- custom memory refresh
- memory interleaving ? different refresh for video memory ? I know there is some performance gains to go there (as the SE did later)
 

cheesestraws

Well-known member
and have seen 32pin ones that are basically just a SIMM with a socket in the back.

Yes, I was going to say, I used to have (before I sent them to a collector of weird RAM) some piggyback SIMMs where you could put your old 256kbyte SIMMS in a socket on the SIMM to avoid having to pay for that RAM again. Maybe this was a cheaper way of doing it for some reason? Who knows.
 

SuperSVGA

Well-known member
Yeah, but there are way simpler ways of doing this. I have the equivalent for 72pin SIMMs upstairs, and have seen 32pin ones that are basically just a SIMM with a socket in the back.
The Dove MacSnap Plus 2 worked like this, but this limited you to 2MB unless you added in 1MB SIMMs, defeating the purpose of the upgrade boards. With these boards you get to 2MB utilizing the existing SIMMs, and can then upgrade to 2.5MB by adding two more 256KB SIMMs or 4MB by buying two 1MB SIMMs rather than four.
 

MacOSMonkey

Well-known member
RAM upgrades were incredibly expensive in 1987-88 and Apple was at the head of the pack on price. In the very early versions of SuperMac RAM upgrades, I think there was some soldering involved. It's how SuperMac originally got started.

And before the OnePlusOne, Enhance and soldered upgrades, animal sacrifice may have been required. 🤪 The OnePlusOne and Enhance upgrades also included fans.

I found an old OnePlusOne datasheet for you -- it may be the only one that still exists! 🤔
 

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MacOSMonkey

Well-known member
Also, FYI, it was originally a Levco product -- like the ProdigySE and SpeedCard boards. It has 32 256Kx8s (1Mb of RAM) and 2 PALs (the 2 logic parts at the bottom that are placed vertically) for doing the address mapping.
 

bigmessowires

Well-known member
I'm nostalgic for the days when companies' ads included their phone number and street address. Maybe you'd stop by and ask the engineers some questions.
 

MacOSMonkey

Well-known member
More SuperMac history and places you can no longer visit. :cry: Here is a rough outline:

More SuperMac history and places you can no longer visit. Here is a rough outline:

950 N. Rengstorff, Mountain View:
In 1987, SuperMac was located at 950 N. Rengstorff in Mountain View. It was just down the street from great burrito joints that also no longer exist -- like La Bamba (near Middlefield) and also Caramba! (on Mary Ave.). During that time, SuperMac sold Enhance, DF20, XP20, XP40 and ... SuperRam 2 and SuperRam 4 (earlier MacPlus memory upgrades). I think the XP40 was $2999.00. The early RAM upgrades that they soldered were for the 128K Macs. Also, they sold SuperSpool and SuperLaserSpool. In 1987, SuperMac also opened an office in London/UK as the drive and software product lines began to expand.

295 S. Bernardo Ave., Sunnyvale:
By late '87/early '88, SuperMac had moved to 295 S. Bernardo in Sunnyvale - with further expansion of the XP drive line and the birth of the video card business with the original Spectrum/8 and ColorCard boards, plus adding the DataStream/DC2000 tape drives and large-format Bernoulli drives (XP60+B), partnering with Levco on hardware expansions, partnering with Dantz for DiskFit and Retrospect, releasing Sentinel, etc. -- all of this was after they had become part of SMS (Scientific Micro Systems). Unfortunately, SMS declared bankruptcy in early 1988. But, SuperMac saved themselves with a management-led buy-out to prevent being sucked into the Chapter 11 vortex. The acquisition by SMS was originally based on synergy with the drive business and use of SMS controllers (MFM/SCSI) in the DataFrame product line. During this era, MiniScribe was famously shipping bricks instead of hard drives (the XP30 used a MiniScribe mechanism). 🤪

485 Potrero Ave., Sunnyvale:
After the buy-out/escape from SMS and continued growth, SuperMac moved to 485 Potrero Ave. in Sunnyvale. SuperMac grew exponentially, rebranded itself as a "High-End Graphics Subsystems Company," easily surpassed a $100M valuation, expanded all the product lines, especially video (including video acceleration + DSP boards) and mass storage (including releasing an optical drive). This era also included the creation of all of the video compression and capture hardware/software, including products based on the C-Cube CL550B (SuperSqueeze), YUV-based VideoSpigot, ScreenPlay, QuickTime Support, Digital Film, Cinepak CODEC, and what eventually became Adobe Premiere (SuperMac ReelTime, aka/codename "Scrunch"). The print/pre-press products also came into being -- the dye sublimation printer, partnership with Tektronix (TekColor), SuperMatch, SuperMac credit in "From Alice to Ocean," and the (I think) RS3000-based postscript RIP. SuperMac's IPO happened in May 1992 while at Potrero.

215 Moffett Park Dr., Sunnyvale:
Post-IPO -- in late 1992 -- SuperMac moved to 215 Moffett Park Drive in Sunnyvale (near Mathilda/237). But...possible clues that things might eventually go haywire as Apple continued to encroach into the video/monitor space may have included spending $100K to re-paint the foyer with a multi-colored spectrum design. SuperMac merged with Radius in 1994 in an $80M stock swap (and attempt to remain relevant in a shrinking market), Radius moved to Moffet Park, and then, despite their Promethean evolutionary arcs at the Dawn of Macintosh, great products and the engineering horsepower of the Dynamic Video Duo, Apple- and Moore's Law-driven pressure of integrated, high-resolution video in machines with very fast CPUs (plus other market factors) led to rapidly-shrinking revenue and eventual corporate collapse.

[Mozart "Requiem" plays quietly in the background as a banner with a brilliant red "S" flutters in the winds of a distant time.]
 
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