Dual Processor Powermac G4 Performance VS. Single CPU?

[bunnspecial]

(unless you're an apple collector like myself).

I'm not really sure I follow your train of thought in this entire thread.

I am a collector too-anyone who's talked to me/been to my house/traded with me can attest to that. I could give you hundreds of examples, but just as one I think it was maybe last spring(2018) that a friend was at a computer show and alerted me to an early '84 "Macintosh" for sale-he couldn't buy it at the time and no one else there seemed to know what it was, but he got me in touch with the seller and I was burning him up to get that computer. It arrived here and I was ecstatic to find a mostly unmolested computer made in the first few months of 1984. That's essentially a useless computer(the memory is a real handicap-the 512k and Plus are much more capable systems that are externally identical) but I wanted the original one. Among people who know me, my "closet of beige" full of new old stock case parts for 90s Macs is somewhat legendary, and I reluctantly dole pieces out from it sometimes.

As to Quads, I bought my first one in 2014. I wanted one as the ultimate PPC Mac, but also wanted to put it to good use-something that I did at the time. I upgdraded it a fair bit-that particular computer has had every available GPU, for example, although it currently has the X1900XT. I've also picked up a few other Quads in the time since.

By your own admission, you collect primarily, and there's nothing wrong with that. Even though I DO collect, I also enjoy putting my computers to good use where I can, so I'm not sure why you're criticizing me for a specific use case I have for a Quad at work. It's in my office-there again-as the ultimate PPC Mac but also gets used for real work.

 

[Appleuser201]

I'm not really sure I follow your train of thought in this entire thread.

I am a collector too-anyone who's talked to me/been to my house/traded with me can attest to that. I could give you hundreds of examples, but just as one I think it was maybe last spring(2018) that a friend was at a computer show and alerted me to an early '84 "Macintosh" for sale-he couldn't buy it at the time and no one else there seemed to know what it was, but he got me in touch with the seller and I was burning him up to get that computer. It arrived here and I was ecstatic to find a mostly unmolested computer made in the first few months of 1984. That's essentially a useless computer(the memory is a real handicap-the 512k and Plus are much more capable systems that are externally identical) but I wanted the original one. Among people who know me, my "closet of beige" full of new old stock case parts for 90s Macs is somewhat legendary, and I reluctantly dole pieces out from it sometimes.

As to Quads, I bought my first one in 2014. I wanted one as the ultimate PPC Mac, but also wanted to put it to good use-something that I did at the time. I upgdraded it a fair bit-that particular computer has had every available GPU, for example, although it currently has the X1900XT. I've also picked up a few other Quads in the time since.

By your own admission, you collect primarily, and there's nothing wrong with that. Even though I DO collect, I also enjoy putting my computers to good use where I can, so I'm not sure why you're criticizing me for a specific use case I have for a Quad at work. It's in my office-there again-as the ultimate PPC Mac but also gets used for real work.

I thought that only using the quad for just one program was a waste of a quad as they have more potential that just that specific program and maybe they could it could be used for something else in addition to what it does? I don't know that program maybe it needs a G5 quad to run smoothly, maybe the quad is still being worked hard. At least your using it, not like some people who have thrown them in recycling.

 

[LightBulbFun]

The problem is that there are no Dual-Link DVI to HDMI adapters, so you're limited to single-link when going the DVI to HDMI route which gives you 18 Hz at 3840×2160. In my experience, OS X will offer 30 Hz in this configuration but it won't work, producing a corrupted image with horribly grainy text. As @LightBulbFun pointed out, you'd need the Atlona DP-400 to go from Dual-Link DVI to DisplayPort and an active DisplayPort to HDMI converter to get 30 Hz on a monitor that only has HDMI.

And 30 Hz is a revelation when you have experienced 13 Hz. No flickering on an LCD of course but man, movement is jerky.

I actually have a Dual link DVI to HDMI cable, but the problem is my Dell monitor does not like a Dual link DVI signal for some reason

if I go HDMI to Dual link DVI to to Dual link DVI to HDMI, then it works fine as an overly complicated HDMI cable, but if I use a dual link DVI source I get a Out of range error, the big question there is would a 4K monitor when fed a Dual link DVI signal into its HDMI port also error out or not?

I THINK @eyoungren is using a Dual link DVI to HDMI on his G5 Quad with a 4K TV, but he can clarify there

 

[eyoungren]

I THINK @eyoungren is using a Dual link DVI to HDMI on his G5 Quad with a 4K TV, but he can clarify there

I am using on of these adapters (only mine is not gold plated):

I have to assume that since I didn't pay much for it, it is not a Dual-Link. That said, I CAN get the full 3840×2160 resolution, but text is not sharp and I have to futz around to arrive at that resolution.

So, from that standpoint yeah, it's probably not dual link.

 

[flyproductions]

The problem is that there are no Dual-Link DVI to HDMI adapters, so you're limited to single-link when going the DVI to HDMI route...

Really?

What about i. e. something like that? It explicitly states 3840x2160 (4K UHD) at 30Hz.

 

[flyproductions]

...and if i take the ten meters it might even reach from the Quad’s current location to the TV! 🤩

 

[Amethyst1]

I actually have a Dual link DVI to HDMI cable, but the problem is my Dell monitor does not like a Dual link DVI signal for some reason

if I go HDMI to Dual link DVI to to Dual link DVI to HDMI, then it works fine as an overly complicated HDMI cable, but if I use a dual link DVI source I get a Out of range error, the big question there is would a 4K monitor when fed a Dual link DVI signal into its HDMI port also error out or not?

I THINK @eyoungren is using a Dual link DVI to HDMI on his G5 Quad with a 4K TV, but he can clarify there

Which cable is it, do you have a link? And if you go HDMI->DL-DVI->HDMI, can you get 2560×1440 at 60 Hz?

 

[Amethyst1]

Really?

What about i. e. something like that? It explicitly states 3840x2160 (4K UHD) at 30Hz.

Reviews state it doesn't work at 2560×1600, which would imply it's not dual-link-capable, so I don't know why it's listed as such. This doesn't surprise me though, as dual-link DVI and HDMI work differently at pixel clocks above 165 MHz - 2560×1600 at 60 Hz as well as 3840×2160 at 30 Hz are in the 260~270 MHz ballpark. Whereas dual-link DVI engages a second TMDS transmitter above 165 MHz, HDMI still uses only a single one. Since a simple (passive) cable doesn't "merge" the two streams, the monitor will either error out or display a corrupted image as it only receives half the signal.

 

[Amethyst1]

I am using on of these adapters (only mine is not gold plated):

I have to assume that since I didn't pay much for it, it is not a Dual-Link. That said, I CAN get the full 3840×2160 resolution, but text is not sharp and I have to futz around to arrive at that resolution.

So, from that standpoint yeah, it's probably not dual link.

IIRC, you said your TV reports the signal as being 1920×2160, i.e. exactly half of 3840×2160 with very fuzzy/grainy text. This is the exact same behaviour my 4K monitor shows when I feed it via a simple DVI-to-HDMI adapter and select 3840×2160. The image really looks as if half the signal is missing which would make sense given how DL-DVI works.

So, I'm fairly sure these supposed "dual-link" DVI to HDMI cables don't work and you need to go the complicated DL-DVI->DP->HDMI route using active adapters that convert the signals properly.

 

[LightBulbFun]

Which cable is it, do you have a link? And if you go HDMI->DL-DVI->HDMI, can you get 2560x1440 at 60 Hz?

indeed, but as you say HDMI is always single stream now whether or not a 2560x1440+ HDMI single stream uses both the physical wires of a Dual link DVI cable would I dont know (sadly I dont have a link it was just a generic Male-male Cable I bought on ebay)

Reviews state it doesn't work at 2560x1600, which would imply it's not dual-link-capable, so I don't know why it's listed as such. This doesn't surprise me though, as dual-link DVI and HDMI work differently at pixel clocks above 165 MHz - 2560x1600 at 60 Hz as well as 3840x2160 at 30 Hz are in the 260~270 MHz ballpark. Whereas dual-link DVI engages a second TMDS transmitter above 165 MHz, HDMI still uses only a single one. Since a simple (passive) cable doesn't "merge" the two streams, the monitor will either error out or display a corrupted image as it only receives half the signal.

aye I had figured something like this was happening with my Dell monitor hence it erroring out on me

(that either it was just getting half a signal which it did not like or it did not like getting 2 separate TMDS signals)


its worth noting that the OS will give me the 2560x1440 option but as mentioned selecting it gives me an out of range error (if I select a "single link DVI" res then it works)

 

[flyproductions]

So - with all that said - the fact, that there is a "4K-capable" PowerMac GPU, is strongly in doubt again?

At least needing one or more active adapters is not exactly following my definition of "beeing capable".

 

[Amethyst1]

So - with all that said - the fact, that there is a "4K-capable" PowerMac GPU, is strongly in doubt again?

If "4K-capable" is defined as being able to display that resolution, there's no doubt this is possible using a PPC Mac. I've successfully driven my 4K monitors from an 800 MHz TiBook (Radeon 7500), an 867 MHz TiBook (Radeon 9000), a Mac mini G4 (Radeon 9200) and a 1.67 GHz PowerBook G4 (Radeon 9700 - that was glitchy though). The issue is that the monitor needs to accept that resolution via DVI (then it's straightforward) or DisplayPort (then you need the Atlona DP-400). And it also needs to support a refresh rate as low as 18 Hz when using single-link DVI or 30 Hz when using dual-link DVI. My monitors meet those requirements.

 

[Amethyst1]

indeed, but as you say HDMI is always single stream now whether or not a 2560x1440+ HDMI single stream uses both the physical wires of a Dual link DVI cable would I dont know (sadly I dont have a link it was just a generic Male-male Cable I bought on ebay)

You're right of course, my bad. One could tear down one of these cables and see if the DVI connector's dual-link pins are connected. Maybe I'll get one and see for myself

its worth noting that the OS will give me the 2560x1440 option but as mentioned selecting it gives me an out of range error (if I select a "single link DVI" res then it works)

It's the same here - when using a simple DVI to HDMI adapter with my dual-link-capable PowerBook G4 and a 4K monitor with only DisplayPort and HDMI inputs, I can select 2048×1152, 2560×1440 and 3840×2160, but the monitor displays a corrupted image. With the Atlona DL-DVI->DP adapter, these modes display fine apart from the UI glitches that appear at the highest resolution. Using a certain 4K monitor with single-link DVI inputs, 3840×2400 works fine at 18 Hz though, apart from the glitches.

So - with all that said - the fact, that there is a "4K-capable" PowerMac GPU, is strongly in doubt again?

At least needing one or more active adapters is not exactly following my definition of "beeing capable".

You can blame the TV manufacturers for only providing HDMI inputs these days...

 

[flyproductions]

I've successfully driven my 4K monitors from an 800 MHz TiBook (Radeon 7500)

So a card like the Rad 7500 which didn't even meet the Cinema 30"'s 2560 x 1600 requirements is able to output 3840 x 2160 if only the refresh rate is low enough? Didn't think that would be possible.

 

[LightBulbFun]

So a card like the Rad 7500 which didn't even meet the Cinema 30"'s 2560 x 1600 requirements is able to output 3840 x 2160 if only the refresh rate is low enough? Didn't think that would be possible.

its down to total bandwidth of a given display connection

as long as your total X*X@XHz stays within the bandwidth of the display protocol your using then it will be able to output it

a 30 inch cinema display wants 2560x1600 at 60Hz which is above the bandwidth a single link DVI port can provide

 

[flyproductions]

a 30 inch cinema display wants 2560x1600 at 60Hz which is above the bandwidth a single link DVI port can provide

Ahh, also didn't know that the Cinema HD is fixed frequency. So thanks for explaining this too!

 

[Amethyst1]

You can push 5120×2880 at 10.8 Hz over single-link DVI No idea if any 5K monitor out there accepts that tho.

# 5120x2880x10.79 @ 31.250kHz
Modeline "5120x2880x10.79"  165.000000  5120 5168 5200 5280  2880 2883 2887 2895  +HSync -VSync

And as for the upcoming Pro Display XDR, it's still good for a whopping 7.8 Hz

# 6016x3384x7.79 @ 26.473kHz
Modeline "6016x3384x7.79"  163.500000  6016 6064 6096 6176  3384 3387 3391 3397  +HSync -VSync

 

[Amethyst1]

Ahh, also didn't know that the Cinema HD is fixed frequency. So thanks for explaining this too!

Many 30" 2560×1600 displays are. The only other supported mode is 1280×800.

 

[flyproductions]

You can push 5120×2880 at 10.8 Hz over single-link DVI No idea if any 5K monitor out there accepts that tho.

Thats when you can clap your hands to the refresh rate?

 

[Amethyst1]

Thats when you can clap your hands to the refresh rate?

In that case, 3.66 Hz would make things easier

# 10240x4320x3.66 @ 15.841kHz
Modeline "10240x4320x3.66"  164.750000  10240 10288 10320 10400  4320 4323 4327 4333  +HSync -VSync

 

[barracuda156]

...and with all that it reached around 3.500 in Geekbench. That’s it so far!

That’s about it. I think I had about 3600, but it won’t get much higher, at least with macOS installed. (BSD should allow for faster GPUs and SSD.)

Having said that, it is not too straightforward. FWIW, I have seen a case where G5 performed better than M1 (I mean, this was clearly ridiculous and implies that the software was horribly optimized for arm64, but nevertheless).

 

[ervus]

On a dual CPU Mac it's pretty easy to boot OS X with one CPU disabled. This allows back-to-back testing to compare single vs dual CPU with whatever software you're using. With CHUD you don't even have to reboot.