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 Pentium III Game Console 

When I complete this project, would you attempt to make it too?
Yes 0%  0%  [ 0 ]
Maybe 67%  67%  [ 2 ]
No 33%  33%  [ 1 ]
Total votes : 3

 Pentium III Game Console 
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Joined: Tue Jan 15, 2013 5:43 am
Posts: 186
FloppidyDingo wrote:
the Pentium III data sheet says that the CPU may operate incorrectly with a clock input of anything other than 100 MHz. I don't see how underclocking could cause issues
One possible reason for sticking to 100 MHz is because an on-chip Phase-Locked Loop (PLL) is used to multiply the original 100 MHz to obtain 600 MHz (or whatever the internal frequency is). PLL's aren't trivial to design, so they've made the job easier by sticking to 100 MHz input -- otherwise there'd be one more variable the PLL design needs to accommodate.

How's your 68K computer coming?

-- Jeff

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Tue Dec 01, 2015 1:07 am WWW
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Joined: Thu Oct 08, 2015 11:57 pm
Posts: 67
Dr Jefyll wrote:
One possible reason for sticking to 100 MHz is because an on-chip Phase-Locked Loop (PLL) is used to multiply the original 100 MHz to obtain 600 MHz (or whatever the internal frequency is). PLL's aren't trivial to design, so they've made the job easier by sticking to 100 MHz input -- otherwise there'd be one more variable the PLL design needs to accommodate.

How's your 68K computer coming?


Oh yeah, the PLL. I forgot about that. I'll just do circuit simulation before I order the board. Also, the chip I have is 800 MHz internally.

The 68K computer is almost finished. Hardware wise. I just need to spend a good session or four to finish the soldering job. For software, I've been getting lazy. I should probably start it. I'm going to set up my Raspberry Pi as a BIOS flasher, and I'm writing a rough draft on what I want my OS to look like. I'll post about it in the other thread so I don't mix it with this one too much. So far nothing exploded, so that's good.

But while I'm on the subject of circuit simulation, I found this site to help me: https://easyeda.com/
Along with being an online simulator, I can also order up to 6 layer boards from them. I'm still looking at it myself, but do you think it would be sufficient for my needs?


Tue Dec 01, 2015 1:19 am
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Joined: Tue Jan 15, 2013 5:43 am
Posts: 186
FloppidyDingo wrote:
I can also order up to 6 layer boards from them. I'm still looking at it myself, but do you think it would be sufficient for my needs?

I think this entire project will take on a startling, new aspect for you after you've gotten your 68K working.

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Tue Dec 01, 2015 1:49 am WWW
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Joined: Thu Oct 08, 2015 11:57 pm
Posts: 67
Dr Jefyll wrote:
I think this entire project will take on a startling, new aspect for you after you've gotten your 68K working.


I'm scared... It's been my life long dream to build this console, and I don't want it to end up as a flop. But you're right, 68K first, console later. I posted a brief about my planned OS.


Tue Dec 01, 2015 2:08 am

Joined: Sat Jun 16, 2018 2:51 am
Posts: 50
Hi
If you haven't already come across these resources, here are some nice ones related to Game Console design.

The MiSTer Project
"MiSTer is an open project that aims to recreate various classic computers, game consoles and arcade machines, using modern hardware. It allows software and game images to run as they would on original hardware, using peripherals such as mice, keyboards, joysticks and other game controllers."

Game Console Architecture Series (by RTL Engineering)
"Series about emulating late 90s era game consoles using hardware instead of software."

Game Engine Black Book Series (by Fabien Sanglard)
The chapters at the end talk a bit about the architecture of the popular consoles of the time.


Tue Jun 16, 2020 8:52 pm

Joined: Wed Jan 09, 2013 6:54 pm
Posts: 1690
Quite a few good blogs too on Fabien's site, picking apart how games were implemented on various platforms:
https://fabiensanglard.net/


Tue Jun 16, 2020 9:08 pm
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Joined: Thu Oct 08, 2015 11:57 pm
Posts: 67
To be honest I completely forgot about this project. And to be fair back when I first started this I had no idea what I was doing. Now I want to revisit this having a lot more experience in electronics. I can already tell this will still be interesting. DDR3 routing is hard enough as it is. These seem like goo links to take a look at though, thank you!


Tue Jun 16, 2020 9:17 pm

Joined: Mon Oct 07, 2019 2:41 am
Posts: 317
Dr Jefyll wrote:
FloppidyDingo wrote:
the Pentium III data sheet says that the CPU may operate incorrectly with a clock input of anything other than 100 MHz. I don't see how underclocking could cause issues
One possible reason for sticking to 100 MHz is because an on-chip Phase-Locked Loop (PLL) is used to multiply the original 100 MHz to obtain 600 MHz (or whatever the internal frequency is). PLL's aren't trivial to design, so they've made the job easier by sticking to 100 MHz input -- otherwise there'd be one more variable the PLL design needs to accommodate.

How's your 68K computer coming?

-- Jeff

Several cpu designs don't use real latches and flip/flops but rather small capacitor
to hold information for a very small amount of time, say 1/4 of your of your master
clock. 100 Mhz clock is 10 ns, and your latch can just hold data for 2.5 ns. Longer than
that *poof* your computer stops working.My guess is that is why you can't under clock.
Ben.
PS: Don't forget the Japanese consoles.


Wed Jun 17, 2020 8:10 am

Joined: Sun Jul 05, 2020 9:00 pm
Posts: 16
One thing to keep in mind for mobile CPUs. Some of the Intel ones started up in battery-saving mode. So you'd need to make sure any BIOS you write is aware of that and can put it in performance mode. I found out the hard way that putting a mobile CPU in a desktop will work, but at a slower speed. I was updating a friend's box and got a mobile CPU, not thinking there would be a difference, that it would achieve the maximum speed listed, but I was wrong. It defaulted to power-saving mode and there was no way to change it, and I couldn't find a utility, such as a driver or configuration utility to run on boot. So, if you run into that, you'd probably want to look into how to access such low-level parameters and set them in your BIOS or wherever.

Another thing to consider with those is the stepping you have and if there were any microcode patches. That is another thing to put in the BIOS. That is hard to find (trade secrets) but some have black-box hacked that and they may have their writings online. Microsoft and Intel both have microcode patches that they give to BIOS makers and OS designers that might not be readily available to the public. Plus such things might have a key or something to let you access those hidden registers. Intel learned the hard way from the Pentium 1 CPU. They had to recall many of those due to a floating-point bug (they used tables and their 9 tables were screwed up). That is why Windows 95/98 had the option in the Device Manager to disable FPU support. It was giving grossly wrong results. And using the OS's FPU emulator hurt performance, though that did allow programs to work more reliably. So Intel came up with a way to use the BIOS or OS to soft-patch the CPU on the fly to fix later-discovered CPU bugs and to sell what would otherwise be considered defective chips, helping their bottom-line and the environment.


Mon Mar 14, 2022 7:48 pm
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Joined: Thu Oct 08, 2015 11:57 pm
Posts: 67
I have heard of the microcode updates, i would be extremely lucky to get my hands on those for a processor that old. I was unaware of the low power mode though. I'll have to look into that. That is, when I revisit the P3.

Right now i'm doing builds with older processors, i'm currently fighting GPU bus issues in a Z80 console, which may need a redesign. My mistake for making an AVR microcontroller do graphics, sound, and IO all at the same time. I am going to offset the graphics to an FPGA. The current design works, but the GPU bus stalls and crashes the system if I use it too much, especially during tile upload calls.

I'm also researching designs around the Power PC, I have several different chips to try, i'm still trying to wrap my head around how the L2 cache works (but i did find a neat PDF that gives example designs for the PPC750). I also have a couple of MIPS R5000s, the problem with that is i cant seem to find the configuration bitstream specs for it. I'm thinking of taking the bitstreams from the other chips and using trial and error to figure it out.

I did experiment with SMPS power supply designs, the first iteration worked well until i tried getting it to output 70 watts, where it met a fiery demise at 12W.

Unfortunately though, boards are expensive and the pandemic has made it quite difficult to acquire chips and afford parts. So progress has been very slow.


Tue Mar 15, 2022 11:59 pm
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Joined: Thu Oct 08, 2015 11:57 pm
Posts: 67
Sugarplum wrote:
One thing to keep in mind for mobile CPUs. Some of the Intel ones started up in battery-saving mode. So you'd need to make sure any BIOS you write is aware of that and can put it in performance mode. I found out the hard way that putting a mobile CPU in a desktop will work, but at a slower speed. I was updating a friend's box and got a mobile CPU, not thinking there would be a difference, that it would achieve the maximum speed listed, but I was wrong. It defaulted to power-saving mode and there was no way to change it, and I couldn't find a utility, such as a driver or configuration utility to run on boot. So, if you run into that, you'd probably want to look into how to access such low-level parameters and set them in your BIOS or wherever.

Another thing to consider with those is the stepping you have and if there were any microcode patches. That is another thing to put in the BIOS. That is hard to find (trade secrets) but some have black-box hacked that and they may have their writings online. Microsoft and Intel both have microcode patches that they give to BIOS makers and OS designers that might not be readily available to the public. Plus such things might have a key or something to let you access those hidden registers. Intel learned the hard way from the Pentium 1 CPU. They had to recall many of those due to a floating-point bug (they used tables and their 9 tables were screwed up). That is why Windows 95/98 had the option in the Device Manager to disable FPU support. It was giving grossly wrong results. And using the OS's FPU emulator hurt performance, though that did allow programs to work more reliably. So Intel came up with a way to use the BIOS or OS to soft-patch the CPU on the fly to fix later-discovered CPU bugs and to sell what would otherwise be considered defective chips, helping their bottom-line and the environment.


Out of curiosity, I looked into the microcode update situation and found some interesting things. I did find an archive of all the microcode update files Intel has made, including the chip I have. And I also read some example code to initiate an update, although I'm not sure if that is for a specific chip or all Intel processors. From my understanding is the update files are encrypted so I myself can't read them, but the processor can so I just hand the whole file over to my P3. Once I can get a functioning board made I can test that idea


Thu Mar 24, 2022 7:21 pm
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