Mac Daniel's Advice

Used 7500 or G3?

Dan Knight - 1999.06.21

JP writes: I just read a bunch of your articles, and I got a kick out of them. If I had more time for writing, I would focus in the same area. My experience is limited between 20 MHz 68030 to 33 MHz 68040, but I sure know just about everything in that range. I almost had a Power Mac 7100, but I gave it to my parents because I couldn't get the 19" Radius Monitor to work.

I'm currently using a "tricked out" Quadra 650, but I will probably be upgrading to a Power Mac next year. Although the Q650 is mostly fast enough, I want to use some programs that are PPC-only. Part of me wants a G3 (yes, I can say Mac OS X), but part of me thinks I could buy a 7500, upgrade it with a cheap 604 card and loads of RAM, and be better off.

As you may know, G3 computers can't use RAM as a startup disk - I suspect running off a RAM disk would dramatically increase the performance. (Using a RAM disk on my Q650 improves Web browsing; when I used a RAM disk on a PowerBook 160, it was noticeably faster.) Heck, with enough memory a 7500 could spin down the hard drive for most normal use, making it much quieter. That way I could also use "sleep" and wake up immediately.

What are your thoughts on that? The $600 difference between a 7500 and a G3/233 would buy a lot of RAM.

It seems strange to me that we still don't see much of RAM disks. When I used it on a PowerBook (which has battery backup), it seemed like a glimpse of the future. With RAM prices as low as they have been and the speed compared to hard disks, I don't understand why the market doesn't move that direction.

Mac Daniel responds: A RAM disk is a marvelous thing, especially on a PowerBook. By treating a portion of RAM as a hard drive, the computer makes less use of the hard drive, thereby reducing power consumption, increasing battery life, and providing faster access to whatever is on the RAM disk. And, as you note, it's also quieter.

The drawback with current desktop Macs is that the Apple RAM disk loses its contents during a restart - earlier Macs, including the 7500, didn't work that way.

I've gone back and forth on RAM disks and disk cache size, finally deciding that the cache is more practical, since it tracks files you're actively working with, whereas a RAM disk doesn't distinguish between active and inactive files. Although I've used caches as large as 7.5 MB (the maximum allowed with current system software), I've generally settled in on a 2-4 MB cache as providing the best balance between improved performance and available memory for all the applications I run.

For a desktop, where you're usually dealing with 32-128 MB of memory and 1-4 GB of disk space, the RAM disk as a system drive really isn't too practical. Better to set up a huge disk cache and let that actively manage files you access than lock up 20-40 MB of RAM (or more!) for a System Folder.

On the other hand, if you keep a very lean System Folder and have the memory to spare, especially on a PowerBook, a RAM disk as startup drive will be fast and quiet.

Given the choice between a Power Mac 7500 at about $600, a G3/233 at around $1,000, and the new Blue & White Power Mac G3 at $1,600, I'd ignore the G3/233 and try to budget for the B&W G3. But since that is well beyond my means, I'd probably find a nice 7500 and drop in a 300 MHz G3 card, which might satisfy me until used G3 Pros come on the market.

My home computer is a Umax SuperMac J700/180 (roughly equivalent to the 7500), which I hope to install a 250 MHz G3 card in soon. At work, I use a 300 MHz B&W G3 - it's an incredibly fast computer and well worth the price if your budget is big enough.

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