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CPU Upgrade / Overclocking Centris 650

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I just found out i'm gonna be getting a centris 650.  The good version with the FULL CPU not the crap version with the LC CPU.  But its still only 25 MHz.  Any way to upgrade this?  I was hoping to maybe overclock it to 40 MHz or 50 MHz.  I havent seen the inside of one of these.  Is the CPU socketed?

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Nice project box you've got coming there, IIRC all the Quadra series had socketed PGA CPUs.




Interesting article, hadn't known serial port borkage was an issue fixed on the Quadra 650 speed bump. There's another possible issue concerning the speed of another MoBo chipset between models IIRC. There's a thread about that topic somewhere, I posted a pic of that section of my Centris board.


Don't worry too much about killing that Centris MoBo in the process of pushing it to the max. I might try it too, a 7100 board replacement is a drop in upgrade  .  .  .

.  .  .  and I've got a handful of G3 accelerators available to turn any Centris into a real sleeper, doubling of 6xx VRAM on the HPV card option is open too. :ph34r:


Edited by Trash80toHP_Mini
the usual
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Centris 650 is a middle-high end machine, a Quadra without the FPU and clocked at 25mhz. In all other ways it is the same as a Quadra 650 or a Quadra 800. Not junk. Q800 was high end, Quadra 650 was the upper portion of the middle high end.


Q840AV - Highsst end once released in 1993

Q950/Q800 - Top end in 1993

Q650 - Middle high

Q610 - Middle

Q605 - Lower middle



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Frankly, I'd probably recommend just leaving it alone and not overclock it at all. At 25Mhz it'll run all the software that's period-appropriate just fine.


That said, per the link on the URL Trash threw out, [url=http://www.applefool.com/clockchipping/c650.html]the only difference other than the clock crystal between a Centris 650 and Quadra 650 motherboard is a couple small resistors.[/url] If you move them you can turn it into a 650 just by swapping crystals, or go faster, with a maximum ceiling of about 44mhz. (You definitely won't hit that with the stock CPU if it's rated for 25mhz; you probably won't even make it to 40mhz with a 33mhz CPU unless you're lucky *and* add a heat sink and fan.)


Per the "exclusivity" question, when Apple introduced the "Centris" name it was an explicit attempt to distinguish the machines intended as replacements for the mainstream "Macintosh II"-branded systems from the then-exclusive high-end "Quadra" nameplate. In other words, they were "middle of the road" machines between the low-end/consumer grade LC/Classic lineup and the exotic "Quadra". It ended up being something of a misfire and in less than a year all the existing "Centris" models were renamed to Quadras. Maybe Apple's customers got stuck on the idea that a machine with a 68040 CPU should have "Quad" in the name?

Basically, a Centris 650 is the sort of thing you'd find in a professional office; not the high-end machine on the graphics designer's desk (that would be a Quadra, probably a 950), but all the managers would have one. The graphics designer *might* buy one to use at home in a "prosumer" sort of role. It's definitely not "educational junk".

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To add: Macintosh LC series machines were also considered competent office machines. Of course, in 1993, you could still buy a fair number of 030 based Macs.


In fact, LC hardware is generally competent enough that the next generation of it launched as a Quadra first with the 630, which is said (by some, not me) to have succeeded the 605, 610, and 650 in Apple's lineup all at once.


The reality of course is that while there were maybe two or three distinct families of physical hardware on sale at once, Apple's product was totally full of unnecessary product tiering. If Apple thought they could get away with it and it would sell them a few units, I have no trouble at all believing there'd have been a Performa 840av.


The fastest way to 40 is an 840av, but I'll add here too that getting to 40 specifically isn't very important, especially if you're running system 7 and 1993's application software and not, say, system 8 and 1996-1999 software (which an 840 will do.)


Realistically, anything you want to do on a Quadra 650/800/950/840 in 1993, you can also do on an LCIII or Performa/LC520, minus any work with cards specifically, and even then, you can often do that work, just without the ability to use the i/o devices.


But, if you want to overclock to ~40, any of the 33MHz systems (and the 25MHz 650 in particular) should do it fine. I know some people who have dropped 33 or 40MHz chips onto C650 boards and run them at a bit over 40MHz to good effect. For their particular workflow, it makes sense, although they happen to have moved onto late PPC macs with G3/G4 upgrades for anything that can run on PPC.

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Actually, there is a difference between the LC 630 and Quadra 630. The Quadra has a full 040, the LC has the 68LC040. 


In general, LC hardware was actually "yesterday's high-end, now in a smaller, less expensive package without all the slots".


Consider the original LC. It had the same clock chip as the Mac II from 3.5 years earlier. Slow data buses made the LC and LCII run slower than the II and IIx, which they share their chips and processor speeds with, but they were still pretty capable, especially considering a sizable majority of the Macs in use at the height of the original LC's popularity were 68000-based (consider how many Pluses and SEs were out there and how many Classics were being sold).


The LCIII, of course, is comparable to the IIci. In fact, the IIci was discontinued when the LCIII came out--or was it simply repackaged into a less expandable version of the same machine? Still, the IIci was very desirable in early 1993, making the LCIII a good option for someone looking for ample power (especially since the Color Classic and Classic II were on the market with considerably slower chips, as were the Performa 400s, which were just LCIIs--not to mention the LCII was still being sold in some markets).


In terms of the Centris line, Apple positioned that to be in the middle of the lineup. (Centris = center). They had the Classics and LCs at the entry level, the Quadras at the high end. Of course, that all changed when the Power Macs hit the market, but it wasn't a bad strategy throughout most of 1993. The reason they didn't use the Quadra name was, as someone mentioned, the fact they needed a way to designated these higher end models as their own line.* Yes, they had the 040s, but since the chip had started trickling down to lower-end models, they figured they'd just try something different. It did backfire in the end!


Since we make a lot of car comparisons on this forum, consider the Centris line to be like the Mercedes-Benz E Class. They're high-end cars to most people, but in the Mercedes hierarchy, they're nowhere near the S Class. Still, they're much further ahead of the C Class in both features and price.


As for overclocking, I wouldn't go any higher than 33MHz, which is what the Quadra 650 ran at. There won't be a huge speed bump, but for certain applications, it will be a modest upgrade.


* Apple apparently wanted to keep the II names going for all modular Macs. The Quadra 700 was code-named "Macintosh IIce". My guess is that it was a "compact, enhanced" Mac II (similar to how the IIcx was "compact extended" and the IIci was "compact with integrated video"). The Quadra 900 was code-named "Macintosh IIex", likely "enhanced extended". I remember some were speculating the LC was going to be the IILC, and I'm sure we've all heard the rumors about the SE/30's potential name. The "II" was from the second overall type of Macintosh, not from the 020, and there was no "Macintosh III" series because Apple had deemed III an unlucky number following the failure of the Apple III--and didn't use the number at all until the LCIII (and didn't begin a model number with a numeral 3 until the PowerBook 3400--note how every other number from 1 through 9 was used to begin the name of at least one model of three digit Mac).

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There are minor variations in a few of the 630 boards, but notably the CPU is socketed, so it's not a huge stretch to note that a "Quadra" and an "LC" shared a platform. Granted, I still think talking about it as though it is a "real Quadra" is a huge stretch, primarily due to it sharing more similarities with the LC/II/III than most Quadras. It's all badge engineering anyway.


The Quadra 605 is also "basically an LC" but perhaps the important lesson here is that Apple would basically have put any label on anything it thought would sell to a particular market. The Quadra 605 and 610 also shipped with LC040 chips, so saying "Quadra means full 040" is not accurate.


The labels, in general, were meant to be:

Performa: home computers

LC: school computers

Centris: office computers

Quadra: workstation-aspirational high end computers, "pro" computers.


Of these, it probably makes sense to list LC and Quadra first since Performa and Centris are both basically branding on the product to make a product sellable or attractive to a certain market. 


The II naming kind of makes more sense in that realistically the main difference between most of Apple's hardware, especially out by 1993 or so, is expansion and exactly how cutting edge something is. Like I said, the LCIII or 475/605 isn't fundamentally incapable of anything you might have bought an 840 to do, but the 840 would do it faster and expansion capability is often a quality of life improvement, esp for people who want, say, multiple displays.


Apple should have called the SE/30 Macintosh IIae.


Apple's product stack was a huge burgeoning mess from around 1989 to 1997. You can look at any year and have to sit there and wonder why, say, both x and y exist, or why either exists when q exists, or why h was introduced as a replacement when a cost-reduced g that it replaced would have better served the market.  (Interesting case in point: Once Performa and LC branding was gone, the Power Macintosh 6500 was still explicitly sold into edu, soho, and home markets. I think the only thing preventing it from being marketed as a corporate office desktop was that the 4400 and 7000 series existed.)


This kind of splitting still exists in the PC industry, although Intel takes care to put a little more differentiation into the processors, and Macs have Xeons now, which often have unique features (today: AVX-512, for example) that can get used by pro apps, making the rift a little wider between an iMac and an iMac Pro than a Centris and a Quadra was back in the day. Even a Centris 610 and a Quadra 950.


I think that badge engineering like that (or, in the PC market, selling particular chips and chipsets in systems designed certain ways) makes sense if your market is really huge and there truly are diverse needs, but I think Apple pretty handily over-estimated exactly how diverse the needs of most Mac users were at the time. (Very the opposite problem they've had in the past few years.)

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The SE/30 was never in the Mac II class, that distinction was made when Macintosh II (NuBus) and Macintosh SE (PDS) series expansion types were released. Until the release of the Quadra 605, NuBus had been the defining characteristic of the II series as well as that of the vast majority of the Quadra lineup that followed. That it's not a full 040 didn't matter much at that point. The 68LC040 powered 605's floating point performance was rated as comparable (a tad better?) than that of the IIfx in the reviews. By the time the Quadra 630 was released, FPU performance had again become a more important issue, so in its Quadra attire, the 630 had the full blown 68040 as standard equipment in its role as the semi-pro low end of the product lineup in the recent PPC makeover.


That SE/30, Quadra 605 and Quadra 630 had PDS without provision for NuBus was in accord with case footprint limitations to available function as outlined in the DCaD series. Designing Cards and Drivers (second edition) added Application Specific Expansion Interface to the NuBus/PDS slot categories to differentiate the IIci Cache Slot from them and provided for later additions to the spec like Video, A/V and CS for example.


The Macintosh IIsi and Quadra 610 series had PDS/NuBus capabilities tacked onto their native PDS implementations. The higher and wider case profiles allowed for NuBus adaptation.


According to everymac, the Quadra 610 (PC) was available in both 68040 and 68LC040 flavors. Was the Quadra 610/full 68040 limited to PC models only, later vanilla 610 versions and/or a price/configuration level thing all along? Very curious that.


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I don't think that there is any proof at all that the Macintosh SE/30 was ever going to be given an "x". As jt says, it wasn't a Macintosh II and didn't need to follow the II's naming convention.


The only reference to this I have literally ever heard is people on forums giggling like preteens about a computer called "sex".


21 minutes ago, Trash80toHP_Mini said:

By the time the Quadra 630 was released, FPU performance had again become a more important issue, so in its Quadra attire, the 630 had the full blown 68040 as standard equipment in its role as the semi-pro low end of the product lineup in the recent PPC makeover.

I think that the FPU was only important for a quadra, but the machine still existed alongside other Quadras that didn't have FPUs. By the time the Power Macintosh family exists, you can argue that any new machine with "Quadra" written on the tin is pretty explicitly for the market that in 1993 was still buying 030s and LC040s - midrange at absolute highest. Basically, the Quadra 630 was aimed at the group of people buying Centrises, and not all of that group needed an FPU.

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Given that, this perhaps solidifies the point that despite Apple trying very hard in the early-mid '90s to make model/family names mean something, they don't and most Mac usage is grouped a lot closer together than people at the ends want to believe, relative to things that aren't Macs.

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41 minutes ago, boitoy1996 said:

Why would anybody ever purposely buy something that wasn't the highest model?

Money, computers were a lot more expensive then, the dollars were worth a lot more back then and the total cost was a much higher percentage of annual income.


I needed FPU support in the SE for software I ran daily. Vectorization of bitmaps would have been glacial without it. TypeStyler transforms were barely endurable done sans FPU on a colleague's SE.



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3 hours ago, Trash80toHP_Mini said:

Money, computers were a lot more expensive then, the dollars were worth a lot more back then and the total cost was a much higher percentage of annual income.


Exactly. And there’s no point in paying for that extra power if you don’t need it.

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I can respect that thought process, but wouldn't it have been upsetting to spend $3000 of your hard earned money, and proudly unpack your new computer only to find out that your office, or your neighbors bought a computer the next month that was a model higher and was faster and better.  I know when things like that happen to me, I instantly feel like what I have is crap and I have to go get the next model.  Keeping up with tech in the 90s must have taken a significant chunk out of a person's wallet.

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Echoing TWF, the internet in the late 90s was a much different beast that it is today.  The majority of sites were still just basic HTML and graphics up until the early 2000s with the features that "broke" older web browsers being things like frames and image maps.  If you take a look at the Space Jam website that will give you a pretty good idea of what it was like at that point, or you can look at sites on the Internet Archive.


AOL is a different beast entirely because for a lot of its history it was a "walled garden" where content was only available in the AOL application and not truly out on the world wide web.



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