TNT and Nitro Board Variations

[cobalt60]

Wondering what the differences are between the the various 7500,7600,7300,8500,8600 boards. One thing I am interested in is bus speed overclock-ability, but really interested to know of any other differences they might have.
For example, a 7300 lacks the A/V input circuitry. Might this help it overclock better? Are there any other differences between the 7300 and earlier boards? Are there any differences between the 7500 and 7600? How about Nitro boards; how are they different from TNT? I believe I have read that Nitro boards support A/V out, which TNT boards do not; is that accurate?

 

[Cory5412]

I'd have to look at some other notes, but you're right, these are all largely the same platform, with various features added and removed per the needs of the product Apple was trying to create at the moment.

Off hand, the one thing to be aware of is that while in theory any of these boards support the same speeds, I've seen it reported that stock cache modules on the 7500/100 in particular tend to be the "best" at varying speeds, because the 7500/100 in particular shipped with the bus set to 50MHz, as the best match to its 100MHz CPU. Most of the other models shipped at ~40-45MHz.

(A point to double-check: what about the /200 models?)

The other way to work around, say, a cache that works at 40 but refuses to work at 50, is to get a different one.

The other main differences:

7500/7600: AV input but not output (main imagined use case seems to be knowledge workers/executives who wanted to do video chatting, but it should work fine for a/v authoring, minus dumping back to tape)

8500/8600: a/v input and output

9500/9600 (and most 6-slot clones): up to 1.5gb of ram and six pci slots, no onboard graphics

7300: same as 7500/7600 but no a/v.

7200/8200: This is probably not within your interest realm because these shipped at soldered CPUs at fixed speeds, but they're a similar overall platform but with a lower RAM ceiling and of course the soldered, rather than slotted, CPU.

This is more on the "historical conjecture" and "product stack planning" but the 7300 is usually framed as a weirdly numbered successor to the 7500/7600, except:
In APAC markets, a 7600/200 existed.

Personal theory:

The 1995 lineup was (excluding the low end)
7200
7500
8500
9500

upon introduction in ~1997, the "new" lineup was:
7300
7600
8600
9600

But in reality Apple was TERRIBLE at numbering and managing the product stack and the hot reality is that the 9500 and the Mac LC 520 were shipping at the same time and the 7200/120 and 6360/160 stayed on sale alongside the "middle" group of PCI PowerMacs (7300-8600-9600/200 in particular) (This is all down to Apple thinking they had a good Capitalism Excuse™ to put more than ten nominally unique product lines on sale, so they overloaded 6 (6360/6400) and 7 (7200/7500) into two each unique product stacks. They did the same thing within the 5-series, the 5260/5280 stayed on sale as a budget-conscious/EduCheap version of the AIO for a fairly long time along the 5400 series, and then a low end 5400 loadout itself stayed on sale below the 5500.) (ultra-ironically, and I know this is getting incredibly into the weeds, but it turned out keeping something like 37 unique models and stock configurations on hand at any given moemnt was absolutely insane bonkers expensive. Once Apple replaced *every* other model with a G3, resulting in basically five products all built with the same parts, they were able to cut the price of every single mac by minimum a full thousand dollars -- the 7300/180 had been $2300, the G3@233 slotted in at that exact same price, in 1998 they discontinued the powermac/233 and re-priced the powermac/266 desktop at 1299, every model above that got the same or similar cut.)

You probably already know this but the 8600/300 and 9600/300-350 are based on a revised version of the architecture, usually suffixed as Mach5/MachV - these put the 1-meg of L2 cache on the CPU card and have a few other differences, all variants run the bus at 50MHz, these are a little more strict about software (shipped with and on-paper require 7.6.1 and an enabler, but these are fast enough to run 9.1 competently IME, so what you choose will basically be down to vibes and needs).

On paper, G3/G4 upgrades and the Apple (and others but I forget which brand) faster 604 upgrades work with any of these machines.

But, whether or not that's helpful really depends on what "overclocking" means to you. If your'e just looking to run the 8500/120 (40mhz bus) at 50MHz, that should work great. I'm actually running a 601@100 in my 8500. If you're looking to try to get the bus to be faster than 50MHz, I'll defer to anyone who has actually done that. For various reasons, I've never bothered.

Hopefully that's helpful // good luck! (definitely put any followup questions in, I or someone who has more bare-metal knowledge than me will be able to help!) (also my apologies for the wall of text and so many sidenotes!)

 

[NJRoadfan]

Note that the CPU cards in those late model 300+Mhz x600 tower "Kansas" architecture machines will not work on earlier boards. For example, a 300Mhz 604e CPU card from a 8600/300 will not work in a 8500 or 7500 board. Aftermarket CPU upgrades like G3/G4 cards are universal, they will work on any PowerSurge platform board.

 

[cobalt60]

Thanks for the thorough reply. Seems like my 7300/200 board may be a good candidate for a bus overclock then; 50MHz from the factory and no A/V circuitry (assuming the A/V circuitry comes into play).

My goals with bus overclocking are just to see what sort of bus speeds would run reliably with no noticeable detrimental effects on stability, and what kind of variation there is in this regard between the boards. When I was younger, I always though these machines had like a hard limit of 50MHz, I never realized they could go faster until recently, so really just curious.

Another thing I am trying to do is figure out how to build my recently acquired 7300. My 2 options are
a) cherry pick whichever of my 4 boards I have that runs at the highest bus speed and use that
b) put my single Kansas board in and build a 604ev system

Kinda leaning towards option b) In addition to it being cool to run a 604ev in a form factor that never ran it from the factory, it appeared Apple thought about adding video out to the 7600, since there are cutouts for it, but never did. And it seems to not be sharing the A/V panel with the 8600, since the 8600 actually (annoyingly) appears molded into the case.

However, the A/V panel is the perfect size to mount 2x 40mm fans. Would be a fun 3D printing project. Main issue (other than sacrificing A/V) is that the 604 heat-sinks have their fins oriented the wrong way to take advantage of fans in that position. I think a few G3 upgrades could take advantage of that though. And of course, a custom heat-sink could be made, too.

 

[Phipli]

(A point to double-check: what about the /200 models?)

Yeah, there are 150 and 200mhz 604/604e based machines with 50MHz busses and 50MHz caches. Many 7500s didn't come with a Cache originally, so I assume 150 and 200MHz machines are the common source of fast cache.

7200/8200: This is probably not within your interest realm because these shipped at soldered CPUs at fixed speeds, but they're a similar overall platform but with a lower RAM ceiling and of course the soldered, rather than slotted, CPU.

Also weird accelerated onboard graphics. I actually find this board interesting now that they're stable in the post 7.5 era. Its a very nice 601 machine if you find a 120MHz model!

7300: same as 7500/7600 but no a/v.

7300, 8600 and 9600 have a different power connector to the 7500, 8500 and 9500... I believe the 7600 has the older style, but would need to verify. The newer boards have more pins on the logic board connector. Does the angle change between some boards too? I forget. Sadly I don't have a 7500/7600/7300 to check.

upon introduction in ~1997, the "new" lineup was:
7300
7600
8600
9600

I'd put the 7600 in the first batch because of the power connector being suspected to be the old style... but to be honest, they're all so similar until the Kansas boards it really is just one computer with multiple configurations.

On paper, G3/G4 upgrades and the Apple (and others but I forget which brand) faster 604 upgrades work with any of these machines.

Except don't put a mach 5 card (250MHz or higher) Apple branded 604ev card in a logic board that wasn't built for it because they changed the card pinout. This includes don't put an 8600/250 card in a 8600/200 logic board.

My goals with bus overclocking are just to see what sort of bus speeds would run reliably with no noticeable detrimental effects on stability, and what kind of variation there is in this regard between the boards. When I was younger, I always though these machines had like a hard limit of 50MHz, I never realized they could go faster until recently, so really just curious.

One thing I mentioned elsewhere to you in passing - RAM. If you're overclocking the bus, get the fastest EDO (rather than FPM) RAM you can. I think there are a small number of 50ns parts out there. 50ns EDO will be about the fastest RAM you could possibly get into one of these machines. The EDO RAM gets run in FPM mode anyway, but apparently tends to have tighter timing than FPM chips, meaning it is more forgiving in fast setups.

Consider VRAM overclockability could also be a bottle neck. Do some struggle at above 50MHz?

Test initially with a minimum config - no cache and a single (fast) RAM stick and only two VRAM sticks. This means you have as few things installed which might choke.

When the computer crashes, try again with a different stick of RAM, different VRAM sticks, different processor - can you get it faster like this?

Once you find the best combo - start adding more parts (cache, RAM, VRAM) - can you keep it stable? Do you need more "golden sample" parts?