Macintosh Plus Logic Board with Brainstorm Accelerator

[CompaqMac]

Hello,

I’m new around here and new to Compact Macintoshes.  

I’m not sure if anyone is interested, but here’s a pic of my Macintosh Plus logic board with a 16Mhz Brainstorm accelerator.  I like this setup because it will allow me to run a beige floppy-only setup, but have some decent performance.  

The logic board pictured below is out of a Macintosh Plus 1MB (beige) from early 1987.

At some point, I’d like to get an SE/30 and maybe another fixer upper Mac Plus to do some mods on.

I really enjoy what I’ve read on this board so far, and I look forward to exchanging ideas and information about these iconic machines.

 

[BadGoldEagle]

Welcome to the 68kmla. 

I'm no stranger to Compacts but I've never seen that kind of Accelerator before. Going from a 8MHz 68000 to a 16MHz 68000 wasn't the most desirable of upgrades as it lacks support for newer instruction sets from the 020 or 030. But I must say that I am impressed by its capabilities. Apparently it performs twice as fast as the stock Plus, basically bringing into to Mac Portable territory.

The upgrade 'card' in itself doesn't seem too complicated either. If it wasn't for that custom IC, it could have been easily reverse engineered!

You can do a lot with these machines. You can add a hard drive emulator (SCSI2SD), a floppy emulator (BMOW FloppyEMU), SCSI to Ethernet adapters and perform additional mods (internal HD, custom ROMs, USB/PS2 keyboards etc). I suppose it's already got 4MB of RAM? With the kind of horsepower you have, you could run System 7 on this puppy rather well I think.

 

[Crutch]

That’s a cool accelerator.  I wonder how its performance compares to my Radius 16 (16MHz 020+FPU, allegedly with some sort of cache).

Side note per BadGoldEagle’s link, why does basically every accelerator seem to break Dark Castle?

 

[Bolle]

Side note per BadGoldEagle’s link, why does basically every accelerator seem to break Dark Castle?

Most of the time it is due to the different cache strategies on the newer CPUs which breaks stuff like timing calculations that rely on how long it takes to run a certain of loop or something along those lines.

 

[Crutch]

Most of the time it is due to the different cache strategies on the newer CPUs which breaks stuff like timing calculations that rely on how long it takes to run a certain of loop or something along those lines.

That’s plausible of course, but even in the earliest versions of MacOS, errr I mean the Macintosh OS there were standardized ways to do that kind of thing (like, the TickCount() system call) that would be robust to adding an accelerator, which by the way I’d assume Dark Castle did, since it actually runs fine (and at the proper speed) on both an unenhanced 512k and a much faster Plus.  I also get that Dark Castle certainly did direct-to-screen bit blitting but even that shouldn’t break on any 512x342 b&w Mac as long as they checked screenBits.baseAddr to decide where to write and didn’t assume a constant starting point for the screen buffer.  I’m actually wondering if it was something with the way they played sound.  Anyway I’m always wondering what developers did back in those days that broke so easily on hardware upgrades.

 

[Bolle]

I was under the impression that sound was only an issue with 030 accelerators.

There were software patches from the various manufacturers but I didn’t see a single one that fixed the crackling sound issues completely.

I also got the impression that the better the sound gets the slower any graphics related stuff gets. That’s especially bad for games.

I always wanted to do a comparison between the different software drivers and fixes for the sound issue and how they affect performance.

You seem to actually understand something about how all that software stuff works. How was sound played back? There must have been calls as well for either sound generation and sample playback. Both cases seem to be affected by accelerators. Even the sound control panel has crackles and pops while putting out the alert sounds as you choose them, so it must be related to some lower level stuff and not the way sound playback is called from software (assuming Apple itself did it their way using system/toolbox calls and not using some magic)

 

[Crutch]

I entirely agree.  I have a couple 030 accelerators in Pluses and the sound quality is pretty bad.  You’re right, there must be something at a lower level with how the accelerated motherboard produces sound because the problem seems ubiquitous with all software.  At some point I might try writing a little program to produce sound a few different ways and try to figure out what’s going on—there were a couple system calls to play sounds, which differed in the older Sound Driver and the newer Sound Manager.  It does seem weird that even using these system calls generates distorted sound on an 030 accelerator, since obviously they sound fine running on a native 030 on a IIci or whatever.

 

[BadGoldEagle]

Just out of curiosity, does your Radius Accelerator 16 exhibit the same sound glitch?

 

[LaPorta]

Side note per BadGoldEagle’s link, why does basically every accelerator seem to break Dark Castle?

Dark Castle was written in straight 68000 assembly language, taking advantage of very low-level processor instructions. I could see it being very easy to make it fail if certain functions were changed/implemented differently via an accelerator.

 

[Crutch]

Just out of curiosity, does your Radius Accelerator 16 exhibit the same sound glitch?

Not in my experience.  But I honestly don’t quite remember.  I will give it a try again and let you know.