Tag Archives: LC

Electronics and Computers, Macintosh, Posts, System 7

Looking for Performa / LC / Quadra 630 Technical Information

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Looking for Performa / LC / Quadra 630 Technical Information

One of the Macs I’m most nostalgic about is the Performa 630 (and it’s many badge engineered siblings). It is a strange derivative of the LC 475, with many similarities, but with a large number of unusual and very specific expansion slots. As well as the LC 475’s LC PDS slot (the 32 bit version), it also adds… An AV slot, a UHF and FM module, a hardware MPEG decoder, a DOS card, a GIMO port and an IR port. It also has SCSI and IDE which can be useful, and a video chip that supports hardware scaling.

Some 630s were fitted with a very similar board also used in the Performa 580. The design is pretty similar, but helpfully provides a second RAM slot.

Technical Info Wanted

I like doing hardware and software projects with old macs but sadly, haven’t been able to find anything much beyond the Developer Note for the Performa 630.

In order of priority, if you happen to have…

  • An ERS for the F108 Memory Controller chip used in the 630 and similar machines…
  • An ERS for the Valkyrie video chip used in the 630…
  • A schematic for the 630 logic board…
  • Anything else similar, the general machine ERS, or technical documentation for other critical chips…

… I would be super interested in hearing. Please let me know. There is a contact form under “About” at the top of this page.

Electronics and Computers, Mac OS 8, Macintosh, Posts, System 7

Installing “Unsupported” Software on an Overclocked LC 475

Installing “Unsupported” Software on an Overclocked LC 475

(Or more generally, installing software on any unsupported classic Macintosh)

You might find that if you have overclocked your LC 475, Performa 475, Performa 476 or Quadra 605 by moving the speed selecting resistors on the underside of the board, you can no longer install some operating system versions, including Mac OS 8.1 for example.

The reason for this, is that the machine id gestalt, effectively the number representing the computer model from the operating system’s perspective, changes when you change the computer’s speed in this way. When you launch some System installers, they check the machine id gestalt, and some, but not all, don’t include the id for a 33MHz LC 475 type computer.

There are three easy solutions for this, depending on your exact needs…

Try Forcing it to Install

Some Apple Installers will ignore the machine check if you hold down the opting key while launching the software. Note this unfortunately doesn’t work with the Mac OS 8.1 installer, but it does work with some older Apple installers. To do this, you can hold it down prior to double clicking, but make sure you keep it held down through the dialogue boxes until you get to the one that lets you pick your install type. At this point, remembering that the installer doesn’t have an appropriate profile for what it thinks your computer is, select “Universal System for any Supported Computer” to make sure everything that is needing gets installed. Note this will be a bigger system install than you really need as it will include all sorts of machine specific extras and even probably PPC code, that your specific computer likely doesn’t need.

Override Your Machine ID

It is possible to set your Machine ID Gestalt in software and there are a couple of different tools for doing it. The most famous one is “Wish I Were”, but for this specific job, it isn’t actually the best choice. Wish I Were is great if you want to change your machine ID long term as it changes it fairly early in the boot process (not early enough if the OS doesn’t support the computer at all, but that isn’t an issue here).

On the other hand, the software “MachID Wannabe”, available here from Macintosh Garden : https://macintoshgarden.org/apps/wannabe-macintosh lets you instantly change your machine ID and it only stays changed until you change it again or shutdown / restart. This is great as without restarting you can change it, then run the installer, and get on with your life. You do still need to install MachID in the Control Panels folder and restart to be able to use it though!

If you’re trying to make an LC / Performa 475 or 476 appear stock, you’ll want to set it to 89. A Quadra 605 would be 94. It doesn’t really make a difference which of these two you pick.

Put the Resistors Back

The third and final option is to just put the resistors back to the default configuration, and instead, install my software overclock Control Strip Module. The module lets you change the speed between more configurations and on the fly. Because the resistors are in their default position, the computer retains its stock Machine ID Gestalt and all installers, software and OSes that check the machID get the expected value for an LC 475, maximising compatibility. I might be bias, but this really seems like the best solution to me!

The latest version can be found here on Macintosh Garden : https://macintoshgarden.org/apps/control-strip-475-overclock

Useful Information

For information about overclocking an LC 475 or related computer, or many other classic Macs, as well as useful information about the machine ID gestalt (commonly called just “gestalt”, although technically the machine ID / machID is one of many gestalts), please check out the amazing http://applefool.com, and specifically http://appplefool.com/clockchipping/.

If you want to know more background about the software overclocking method, check out my post here, and the original 68kmla forum thread by mustermann here.

Electronics and Computers, Macintosh, Posts

How Much Memory Does My Vintage Mac Really Accept?

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How Much Memory Does My Vintage Mac Really Accept?

In the early days of Macs, Apple stated the theoretical maximum memory a Mac could use. But with the Macintosh II, a mixture of issues meant that in reality, you really struggled to reach the theoretical 128MB. There were ROM bugs, you needed a Memory Management Unit upgrade, there was no 32bit addressing and the standards for RAM changed meaning the Mac II and IIx accidentally trigger a test mode in normal 4MB SIMMs and crash.

They got sued.

As a result, there after, Apple generally only quoted the maximum RAM a computer had been tested with during development, which was usually, but not always less than the actual maximum.

Note that maxing out the RAM on a Mac will make the built in RAM test take as long as 2 minutes in some cases. During the test the computer will sit with a black, empty screen. On later OSes, possibly from about Mac OS 8.5 onwards, it is possible to disable the Memory test with a hidden option in the Memory control panel. If I remember correctly, it appears when you open the control panel with the Command and Option keys held down.

For Apple’s official recommended maximum RAM for each machine, please see the Service Source document “Apple Memory Guide” from 1998. Where I haven’t included a machine on this page, either Apple’s maximum actually applied, or I’m unfamiliar with the model. Apples maximums apply to machines including the… Plus, SE, Classic, Classic II, Colour Classic, LC, LC II, LC III, IIvx, IIvi, IIci, IIfx, Quadra 660av, Quadra 840av, Quadra 900, Quadra 950, Performa 6200, Performa 6300, Performa 6400, Performa 6500, as well as other machines that are very similar (such as the 5*** series equivalents to 6*** machines, and Performa equivalents to LCs).

I’m not very familiar with PowerBooks, so have mostly excluded them.

Actual Capacities and Observations

The following does not consider hacks or modifications to ROM or hardware, but only what can be easily done by any user.

Macintosh II / IIx

128MB, but you’ll need IIx ROMs and a MMU in the Mac II, plus both need PAL SIMMs and either a 32bit clean ROM, or MODE32.

See Apple Memory Guide for how to correctly fill the two banks of RAM.

Macintosh IIcx & SE/30

128MB, but your’ll need a 32bit clean ROM or MODE32.

See Apple Memory Guide for how to correctly fill the two banks of RAM.

Macintosh IIsi

The IIsi will take four 16MB SIMMs plus the 1MB soldered, for a total of 65MB. Set your hard disk cache to 1MB for improved CPU performance due to a quirk of the video circuit design.

Performa / LC / Quadra 630 & LC / Performa 580

There are two logic board variants. A one RAM slot machine will take up to 128MB plus the onboard 4MB for a total of 132MB. A two slot machine will take up to 196MB. Note the second slot only works with 4, 16, or 64MB SIMMs.

The LC / Performa 580 uses the same board as the two slot 630.

LC / Performa 475, LC / Performa 575 / 577 & Quadra 605

These machines will accept a 128MB SIMM, for a total of 132MB including 4MB onboard.

Centris / Quadra 610

A quirk of the ROM in these machines means that even though the hardware is capable of seeing banks of up to 64MB, the ROM only checks for 32MB banks at most. There are up to two banks per SIMM, but not all SIMMs have two banks. Weirdly, this means that the most RAM you can fit is 128MB + onboard RAM (4MB) for 132MB total, but because 64MB SIMMs are usually single bank, you need to fit two 128MB SIMMs. The computer recognises each 128MB as two 32MB banks instead of two 64MB banks, but otherwise works fine.

Quadra 700

The Quadra 700 accepts up to four 16MB SIMMs plus 4MB of soldered RAM, for a total of 68MB.

Upgrade with a matched set of four.

Quadra / Centris 650 and Quadra 800

A quirk of the ROM in these machines means that even though the hardware is capable of seeing banks of up to 64MB, the ROM only checks for 32MB banks at most. There are up to two banks per SIMM, but not all SIMMs have two banks. Weirdly, this means that the most RAM you can fit is 256MB + onboard RAM (4 or 8MB) for a total of 260 or 264MB, but because 64MB SIMMs are usually single bank, you need to fit four 128MB SIMMs. The computer recognises each 128MB as two 32MB banks instead of two 64MB banks, but otherwise works fine.

Upgrade in matched pairs for improved performance due to memory interleaving.

Power Macintosh 4400

You can fit two 64MB SIMMs and one 32MB DIMMs for a maximum of 160MB. Thanks to D Cook for confirming this for me!

Warning : This machine requires 3.3V 168 pin DIMMs. Very unusual for this era of Macs.

Power Macintosh 6100

The Power Macintosh 6100 can actually recognise two 128MB SIMMs, plus 8MB onboard for a total of 264MB of RAM.

Upgrade with matched pairs.

Power Macintosh 7200 / 8200

Technically, the 7200 could recognise 768MB if you could find some 5V, FPM, 256MB SIMMs, short enough to fit in the chassis. I’ve never seen any. That means you’re likely looking at 384MB, which will be expensive as 168 pin 128MB 5V FPM DIMMs are not cheap.

Power Macintosh 7500, 7600, 7300, 8500 and 8600

Technically, if you could find 256MB 5V FPM or EDO DIMMs that fit the chassis, the maximum would be 1.5GB of RAM (limited by the OS). I’ve never seen any that aren’t too tall. That means you’re likely looking at 1GB, which will be expensive as 168 pin 128MB 5V FPM or EDO DIMMs are not cheap.

Can be upgraded individually, but works better with matched pairs.

Power Macintosh 9500 & 9600

With 12 slots, these will take up to 1.5GB using 128MB 168 pin, 5V FPM or EDO DIMMs.

Can be upgraded individually, but works better with matched pairs.

Power Macintosh G3 (Beige)

These machines will accept three 256MB PC66, PC100 or PC133 DIMMs for a total of 768MB. The DIMMs need to be physically short to fit in the desktop case, and additionally, “high density” DIMMs do not work. Practically, this means you need physically short DIMMs with 16 chips (eight on each side).

PowerBook G3 Pismo

Some (but not all) 512MB PC100 and PC133 SODIMMs work in the Pismo, for a maximum of 1GB of RAM.