Why Am I Having Problems with My 1 MB L2 Cache?

1999 – It’s been three weeks since my last column, yet the email keeps pouring in. I hate to admit it, but I’m about two months behind on your letters, so I’ll be keeping a low profile on Mac Daniel (one or two columns a week) until I catch up.

JB writes: Thanks for your Web pages of Mac advice. I find it very useful and quite interesting. I read about all of them. It has answered several questions I had about my three Macs: a Centris 650, 7200/120, and 7300/200. Over the years I have owned a total of nine Macs.

None ever gave me any major problems. I have run all Mac systems since System 6.0.x. I do find all the later OSes are not aimed at Mac owners like me, so I usually end up with only the real operating system and trash the rest.

The old C650 is now used just for running text, email, and dedicated light Internet use. I keep it because I can best run older programs on it using System 7.5.5. It also has a graphics card.

Power Mac 7500The 7200/120 is not all that bad with a 1 MB Level 2 (L2) cache and faster hard drives. It is said by many to be a slow Power Mac, but since speed is not across the board, it is not exactly a slouch. I don’t intend to consider upgrading it unless a G3 card is made for it – probably one that runs in the cache slot. If they ever make one, I will buy it. I use it with PageMaker and other black and white graphics software. No, I don’t use color. But this box does run a color scanner and an Epson 800 printer. It runs Mac OS 7.5.5, 7.6.1, 8 and 8.1 on partitioned hard drives, and 8.5 on an outboard drive.

Apple LaserWriter IINot liking the later G3s for several reasons, mostly that all my hard drives are SCSI and 7200 RPM types, and that investment alone is worth considering. I can also move them when necessary. I recently bought the 7300/200 new for about what the G3 would have cost. In what I do, I don’t really find it is a lot faster than the 7200/120. This box runs 8.5 and 8.1 on two drives. I use the latest DTP software I have on this box. It runs a LaserWriter IIf. 300 dpi that is excellent for what I do, plus I can run a font hard drive with it.

All boxes run 17″ Sony monitors and can be Internet used. All boxes have in excess of 70 MB of RAM. Most run partitioned 7200 RPM 4 GB or smaller hard drives, which are a considerable speed boost themselves. No, I don’t run SCSI cards with these drives.

Finally, my question. I decided to move the 1 MB L2 cache from the 7200 to the 7300. It worked okay, but I experienced frequent crashes. I switched back, and the problem went away. Is there a special L2 1 MB cache for the 7300? Or is it just the brand of cache I have?

Mac Daniel writes: Your 7200/120 is a very nice computer. We have several at work, and they are very reliable.

A stock PowerPC 604 is about 50% more powerful than the 601 in your 7200. That means a 200 MHz 604 would roughly equal a 300 MHz 601 – if they’d ever made a 601 that fast. But with a 1 MB L2 cache, you nearly double performance of the 7200 vs. no L2 cache at all. It’s also about a 60-70% boost over the 256 KB L2 cache that is most common.

Based on that, your 7200/120 with a 1 MB L2 cache is probably within 30-40% of the speed of your 7300 with a 256 KB L2 cache. But you could change all that and get double the performance of your 7200 by putting a 1 MB L2 cache in the 7300.

The reason your cache is stable in the 7200 but not the 7300 has to do with motherboard speed. The 7200/120 runs the motherboard at 40 MHz, so that’s all the speed the L2 cache needs to support. The 7300/200 runs the motherboard at 50 MHz, so it often happens that a cache designed to work at 40-45 MHz won’t cut it at the higher speed.

You need to specify that you want a 1 MB L2 cache for the 7300 to make sure your dealer gets you one fast enough to work properly on a 50 MHz motherboard.

Keywords: #level2cache #l2cache #powermac7200 #powermac7300

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