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In previous articles we covered both the nearly identical LC and the LC II, both of which were early attempts to bring an affordable color Macintosh to the market. Both machines more or less accomplish what they set out to do but also both were heavily compromised in functionality to achieve this end.  The main compromises of the original LC and following LC II were

1 – A 32-bit CPU on a 16-bit motherboard severely hampering the performance of the LCs 16mhz 68020 CPU.

2 – An imposed limit of 10MB of RAM regardless of the size of the RAM stick(s) installed.

3 – complete lack of a MMU or FPU socket on the motherboard.

4 – Difficulty getting the LC to run with monitors outside of the fixed resolution 512×386 monitor it was intended to be paired with or period Apple or early VGA monitors.

The LC II added the ability to use virtual memory via the CPU’s built in MMU and tweaked the video a bit but was otherwise identical. Thankfully the LC III finally addressed all the above issues while maintaining the same small form case. Finally we have a full 32-bit data bus so as not to strangle the 32-bit CPU. There is now a MMU as there was built into the LC II but also much more expandability for RAM as well as a socket for a FPU chip and the video memory supports 640 x 480 resolution without any kind of fiddling or upgrade.

Other then the LC III badge the case is identical to the LC I and II. bear in mind there are two versions of the LC III case and one features a manual eject floppy drive that looks a little different with an indentation to grasp the disk. These cases also have the case badge as more of a label then etched onto the case. Otherwise these machines are identical.

The rear of the case though is identical to the LC I & II. from left to right you have the power connector and switch, Mac video port, modem and printer ports, external SCSI port, ADB port and finally an audio jack for speakers and mic. The Ethernet card installed on the right is the same one that used to be installed in my LC II.

The LC III like the LC I & II does not support power on via the keyboard and use of the rear switch is required. Opening the LC II is exactly the same as the other LC’s with just two fairly sturdy tabs securing the top.

Now with the top removed.

The general layout is basically the same as it was in the LC II with a single floppy drive and space for a SCSI hard drive. Mine came with a standard 80mb SCSI hard drive but I upgraded mine to a 500mb model by transferring the upgraded hard drive from my LC II.

Now lets take a look at the motherboard.

1) Enhanced LC PDS slot – The PDS slot on the LC has a slight extension to it compared to the PDS slot in the LC and LC II. The “enhanced LC PDS slot” in the LC III supports both 16-bit PDS cards of the type that would be used in the older LC machines but also 25mhz 32-bit PDS cards. Unfortunately these 32-bit cards are quite uncommon.

2) CPU – The LC III unlike the LC I & II now uses a full 32-bit data bus as opposed to a 16-bit but so the CPU can be taken full advantage of. The CPU in the LC III is a Motorola 68030 running at 25mhz, also a bump up from the 16mhz of the previous LC’s.   Some benchmarks of the time placed the LC III twice as fast as the LC II in overall performance. There is also a version of the LC III known as the LC III+ which is identical save for the CPU which got a speed bump up to 33mhz. There is no way to tell the two models apart as there was no indication given on the outer case. Only opening the case and checking the CPU or powering the machine up and checking in software would reveal the difference. There are guides available on modding the LC III into an LC III+ but perform at your own risk. Also Later LC III’s with the manual floppy drive eject are more likely to be the plus models though be aware this isn’t a sure thing.

3) FPU – Finally we have a socket to add an optional 68882 math coprocessor to assist in complicated math calculations. This doesn’t seem to of been a popular upgrade though as I’ve never come across an LC III with this upgrade though the chips are fairly cheap (as of 2018).  Like on the x86 PC though I don’t think the FPU was heavily utilized in any number of games on the Mac so the FPU upgrade was not seen as a priority.

Empty FPU socket to the right of the CPU

68882 coprocessor installed

4) RAM – The LC III has 4mb of RAM on the motherboard but also unlike the previous LC’s the LC III has a single 72 pin SIMM socket with the ability to add up to 32 additional MB or RAM for a potential max of 36mb. This is the configuration of my LC III featured here. The LC III was also the first Macintosh to use 72 pin SIMMs. This was a welcome feature as the previous 10mb was serviceable for the time but the ability to add up to 36MB total went a long way to extending the usefulness of the LC III in the future.

5) Video – The LC III features built in video and 512kb of VRAM standard. This allows 640 x 480 resolution on a 640 x 480 capable monitor out of the box and I had a much easier time hooking this LC up to my various monitors via a Mac to PC VGA adapter and getting a image without any hassle or “out of range” errors. The VRAM is upgradeable to 768kb via a VRAM slot and 256 KB 100ns VRAM SIMM. This will allow a maximum resolution of 832 x 624 at 16-bit

6) PRAM – this is the ever present PRAM battery for saving settings. It is always recommended to swap this battery out when you get a new Mac or if you start encountering strange instabilities.

The Mac LC III was a great evolution of the LC line finally fixing all of the shortcomings of the line while maintaining a lower price point. For all intents and purposes the LC III was a Macintosh IIci in a smaller form factor case with slightly lower performance and much less expansion capabilities. If all you wanted to do was some light work and gaming and didn’t need the expansion slots of the Macintosh II line the LC III was an excellent option that saved money and took up a little space in the house.

For the retro Mac gamer I would easily recommend this machine over the LC I and II. They don’t take up much space, are light and relatively cheap and easy to fine. They also offer enough power to run early color Macintosh games or black and white titles well and can work with most monitors hassle free.

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8 Comments

  1. You can add a FPU to your other LCs easily. Most Ethernet cards provide an empty chip socket for a MC68882. But the narrow bus strikes again. On a Mac II hardware FPU benchmarks are _multiple_ times faster than software (SANE) based ones. On my LC I with FPU my FPU-optimized programs are running only _twice_ as fast (OTOH not too shabby for a real world speed improvement).

    In old times you had to throw a compiler-switch if you wanted your program to make (direct) use of a hardware FPU, otherwise it used Apple’s SANE math-software-library. (SANE = “Standard Apple Numeric Environment”, a code library responsible for the time-consuming, therefore slow, task of translating even high precision floating-point operations into simpler portions of code a standard 68k-CPU can handle.) And only few software titles will find improvement from it. I faintly remember only one game (“Color Billiards”?) that uses floating point math for modeling collisions (which is in fact totally unnecessary, as integer-based approximation would be sufficient; that’s how it is usually done in games). Otherwise games are mostly not effected.

    BTW, the additional PMMU in the MC68030 doesn’t help much, since virtual memory on 680×0-Macs is performing very poorly. It makes your Mac slow. All graphic artists I knew had virtual memory always disabled. The only software that really needs a PMMU are UNIX-implementations like Apple’s A/UX (however, not sure about Photoshop’s own virtual memory management). A/UX will not run on any LC anyway.

    2 minor corrections: (Number 4 at the beginning) LC I and II’s video circuits are compatible to plain VGA-monitors, not SVGA. And: (Every!) LC supports 640 x _480_ video – not “640 x _400_” (640×400 was used in early PowerBooks). But LC and the LC II are limited to 16 colors/grays unless you have a VRAM extension.

    • I made some corrections to the article based on your info. I think 640 x 400 was a typo though.

      I usually always turn off virtual memory. even on a Power PC its caused issues for me making some games stutter. Also thanks for confirming the usefulness of the FPU in Macs for games. it’s what I suspected.

  2. Some comments about Macs for retro-gaming, LCs and other.
    My favorite LC is the LC/Performa 475. The 475 is to the Mac Quadra what was the original LC to the Mac II. While not exactly as fast as the expensive Quadra, its 68×040-processor offers a substantial performance gain compared to all 68030-based Macs at a fraction of a Quadra’s price. Only its additional cache may be incompatible with really old apps/games. Control panels like Apple’s “Cache Switch”, manually disabling these caches, are sorting this out. There are also control panels switching 68020/68030’s code and data caches, very recommended for very old games. Low cost and portable 040-Macs are using the low-power 68LC040, which is stripped of its FPU (but a full 68040 may be swapped in, since the processor is socketed in a LC475). As discussed before, this does usually not cripple games – since old games usually do _not_ use a FPU!

    However, if you like games for the 68k-processor-family, especially from the 1990s, nothing works as fast as any G3/G4-Mac running System 8.5-8.6 or 9.0-9.1 (maybe also 9.2.x). The G3/G4 is the ideal match to Mac OS’ internal 68k-emulator resulting in multiples of the performance of any LC. A bondy-blue iMac flies with these games – and also offers decent screen resolution and color-depth. Apple’s 68k-emulator/recompiler is fast (from System 7.5.3 onwards, older versions are slow), reliable and works for everyday apps too: Ancient MS-Word version 5.1 (the famous one from 1991, see: https://www.wired.com/2004/06/word-refuseniks-never-upgrade/ ) felt so fast, I wrote most of my PhD-thesis with it on an 300 MHz G3 iBook.

    (Thank you for corrections. One 400-typo is still in the paragraph _after_ “4.” at the top of your article.)

    • Thank you for the comment and good information. comments like that really help others that stumble upon this little site looking for info. I’m going to keep an eye out for an LC 475 now as it looks like a really nice system for playing older stuff on period hardware.

      My go to Mac for 90’s games is actually a 300mhz G3 desktop. Currently running OS 8.5 since Ive had trouble finding a good link to the 8.6 update online.

  3. This is awesome! I am going to advertise this on greatgamez.wordpress.com! Thanks!

  4. Looks like you have some leaky caps on that board. You might want to replace them and clean up the residue before it causes some damage.

    • you are correct. seems pretty much every Mac from this era I come across has leaky caps including all the LC’s I’ve acquired. Thankfully it’s more or less repairable if your decent at soldering…which I am not.


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