dlt@csuna.csun.edu (Dave Thompson) (06/15/89)
I called Microtech today regarding their 68020 accelerator for the Mac+. It seems that this is only a 8MHz processor. I was told that a faster processor would be a waste of money because the bus only runs at 8MHz on the Plus. Supposedly this board gives you a 30% - 50% increase in speed. I question whether this is a worthwhile improvement for $599. Of course, a MacII costs a bit more than that (:-)!!), but isn't there a four-fold increase in speed between that Mac+ and the MacII? -- Dave Thompson uucp: dlt@csuna.csun.edu Computer Center Cal State University, Northridge phone: (818) 885-2790 18111 Nordhoff Street, Northridge, CA 91330
dwells@Apple.COM (Dave Wells) (06/15/89)
In article <2042@csuna.csun.edu> dlt@csuna.csun.edu (Dave Thompson) writes: >I called Microtech today regarding their 68020 accelerator for the Mac+. It >seems that this is only a 8MHz processor. I was told that a faster processor >would be a waste of money because the bus only runs at 8MHz on the Plus. >Supposedly this board gives you a 30% - 50% increase in speed. I question >whether this is a worthwhile improvement for $599. Of course, a MacII costs >a bit more than that (:-)!!), but isn't there a four-fold increase in speed >between that Mac+ and the MacII? There are a number of 3rd party accelerators which use the 68000 and run at 16MHz. They provide a speed improvement of about 50% and cost around $300. They typically obtain the speed increase by running their bus at the higher speed and using a small amount of fast (static or dynamic) RAM to cache the slower motherboard RAM. (much as the RAM cache in the control panel does for disk access) Off the top of my head, two I can remember are made by Siclone and AOX. Maybe Dove too? The accelerator option that became the rage about 1.5yrs ago and is still very popular uses the 68020 and typically runs at 16MHz, though higher speeds are available and are increasingly more common. (along with 030 versions) These will increase CPU performance to roughly that of a Mac II (at 16MHz) or beyond. Sometimes faster and sometimes slower, depending on the task. They use varying on-board RAM strategies like fast static cache RAM or sockets for faster dynamic RAM like that used in the Mac II. They will cost much more than the 68000 accelerators and can get downright spendy if additional RAM is required (for non-cacheing designs this is required to avoid massive slow-downs induced by wait-states for the motherboard RAM.) In the early Mac accelerator days a few 68020 based models were available that ran at 8MHz. The performance gain, though modest, was there, and they provided a 020 development platform at a low price. There are newer designs around now and they do still provide these benefits without requiring the purchase of additional, faster RAM like some 16MHz models need. They are in the middle ground on price because they use slower (less expensive) components and require less support components than the 16MHz versions which are usually almost complete computers on a board. All provide some sort of performance improvement. You need to determine exactly what you want to see go faster. There are models of each type that accept 68881/68882 numeric processors. (to speed up calculations beyond that possible with chip speed increases.) There have also been 020 models that accept a 68851 PMMU. This will be required for virtual memory & such with future system releases, though the new 030 accelerators would probably be the wiser choice. Oh yea, what the person you spoke to probably meant (I hope) was that using a 16MHz rated 020 in the accelerator wouldn't increase the speed because this particular accelerator runs at 8MHz. I'm assuming this because motherboard bus speed is somewhat irrelevant in regards to the issue of increasing computer performance. Actually, that 8MHz motherboard clock speed is a large motivating factor in the whole concept of accelerators. -Dave -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Dave Wells, Apple Computer, Inc. MS: 37-O (408) 974-5515 Mail: dwells@apple.com or AppleLink d.wells or GEnie D.WELLS These opinions may be nothing more than the ramblings of a fatigued tinkerer -=-=-=-=-=-=-=-=-=-=-=-=- There's one big difference between genius and stupidity. Genius has limits. -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-