what is fixed xe (g4) dma and usb hardware

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what is fixed xe (g4) dma and usb hardware

Postby msalcedo » Sun Jul 28, 2013 1:09 am

Hey all,
I just aquired a used g4. I found out it refered to the dma and usb hardware fixes.
How does one determine if it is in fact fixed?

As I've added a new ide drive and re-installed the os. Because the machine is a little flakey, I was wondering if this was the problem?

Thanks in advance,

It wasn't the problem, the memory stick was!
Last edited by msalcedo on Tue Jul 30, 2013 12:40 am, edited 1 time in total.
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Re: what is fixed xe (g4) dma and usb hardware

Postby tonyw » Sun Jul 28, 2013 8:34 am

The XE motherboards had a few flaws that only showed up after they had been released and tested using real software. The main problems were "The DMA problem" and "The USB problem", but there was also the "On-board sound" problem:

The DMA problem: because of bugs in the VIA southbridge (which was designed to run with an x86 bus), there was a problem with data transfers using DMA if the on-board IDE interface and the on-board Ethernet interface tried to send/receive data simultaneously. It can be fixed by cutting a couple of tracks and adding a couple of wires to the back of the board, but it has the side effect of preventing use of the 66 MHz PCI slot for video graphics. A better solution is to use a plug-in PCI card for disk interface - these days you'd be better off with a 2- or 4-port SATA card, anyway. As long as the card has a 3112/3114/3152 chip set, it'll work OK with existing drivers.

The USB problem: because of lack of documentation of the VIA southbridge, terminating resistors for the USB ports were omitted from the motherboard. They can be added easily by anyone with a soldering iron and good eyesight. The four USB ports on the board need to have a resistor of 12-15 kOhms connected from each data line to ground. These resistors are usually added on the back of the board, soldered across the pins of the sockets. Some people have removed the 47 pF EMI caps from the data lines and replaced them with SMD resistors, but that is a tricky job unless you are experienced with SMD.

The On-board sound problem: when the XE board was first released, no one could get the sound chip to work, so it was assumed that there was a wiring fault and it was left off the later manufactured boards. Later still, it was discovered that an undocumented enable bit in a southbridge register had to be turned on to make it work. If you are lucky, you might have an early board that had the sound chip installed. If yours is a later board, the sound chip can be added afterward by someone who knows what he is doing, but it's fiddly and the on-board sound is only average in quality anyway. A better solution is to use a plug-in audio card.

If your XE is "flakey" (and a lot of them were), it may be because of the memory. I've tested and worked with a lot of XEs, and they all behave differently. Some of them will run with two memory DIMMs, but most will only run reliably if you have a single memory DIMM installed. It is getting harder these days to find suitable memory for the XEs (it's old technology now), but you should be able to find a 512-MB DIMM at a second-hand market or on line. I would advise against trying to use two DIMMs - you'll likely get better reliability out of a single.

The mounting of the CPU module is another cause of problems. The CPU module is supported on two M3 tapped nylon spacers that are too long, and the CPU module sits crooked because of it. If you (or a kind friend) remove the spacers and cut about ½mm off each one, you'll be able to get the module to sit parallel to the mobo and it might cure some intermittents.

Lastly, the XEs are famous for being very touchy about their 3V clock cells. The voltage of a new one is usually about 3.2 V, but once it falls below about 3.0 V, the machine crashes or won't boot properly. Fortunately, they are cheap and can be found at any supermarket or chemist/drugstore/pharmacy.
cheers
tony
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Re: what is fixed xe (g4) dma and usb hardware

Postby msalcedo » Sun Jul 28, 2013 9:12 am

@tonyw
Excellent response! Many, many Thanks.

I now know how to proceed.
check, I replaced the battery
check, I pulled out an old nec usb card
It's better already.

I like the idea of sata better, so tomorrow I will look for a pci disk interface card

Thanks again,
Michael

newbie once again
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Re: what is fixed xe (g4) dma and usb hardware

Postby ZeroG » Sun Jul 28, 2013 9:30 am

tonyw wrote:A better solution is to use a plug-in PCI card for disk interface - these days you'd be better off with a 2- or 4-port SATA card, anyway. As long as the card has a 3112/3114/3152 chip set, it'll work OK with existing drivers.

I think U-Boot 1.1.1(Mar 3 2005, latest non-beta firmeware) only supports cards with sii0680 (PATA) and one of the cards you named. I think it was the sii3112 (2-Port SATA).
There is a beta U-Boot 1.1.4 that add support for one more card, i think it is the sii3114 (4-Port SATA).
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Re: what is fixed xe (g4) dma and usb hardware

Postby tonyw » Sun Jul 28, 2013 1:17 pm

You may be right there. I forgot that I have a "special" beta version from 2007. I can't remember what's special about it, but it was never released because it was an experiment that broke something. I rather think it was the ability to boot from some source that I don't use, but it was years ago now.
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Re: what is fixed xe (g4) dma and usb hardware

Postby nbache » Sun Jul 28, 2013 1:43 pm

tonyw wrote:As long as the card has a 3112/3114/3152 chip set, it'll work OK with existing drivers.
Actually, the third one should be 3512, not 3152. (Whether there is boot support for that, I'm not sure.)

Also, I am almost sure the 3114 boot support came before the 3112 one.

Best regards,

Niels

(who is actually still booting the XE G4 from the builtin IDE in PIO mode).
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Re: what is fixed xe (g4) dma and usb hardware

Postby msalcedo » Mon Jul 29, 2013 5:22 am

@nbache
Could you please explain about the "pio" thing?

I too am booting from the ide first connector with a maxtor 200gb drive. (three part sys, swap and work) It works...
and the second ide port with cd/r master and cd slave. Both work.
But as I bring in other files, like the updates and the sdk. Or I try to unlha and/or install.
The system sometimes hangs On reboots, it finally suceeds.

TIA,
Michael
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Re: what is fixed xe (g4) dma and usb hardware

Postby daveyw » Mon Jul 29, 2013 11:47 am

tonyw wrote:A better solution is to use a plug-in PCI card for disk interface - these days you'd be better off with a 2- or 4-port SATA card, anyway. As long as the card has a 3112/3114/3152 chip set, it'll work OK with existing drivers.


Can the A1 boot from SATA? I didn't think it could?
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Re: what is fixed xe (g4) dma and usb hardware

Postby salass00 » Mon Jul 29, 2013 1:58 pm

msalcedo wrote:@nbache
Could you please explain about the "pio" thing?


PIO means that the CPU is used to reading and writing rather than UDMA (it also means that disk transfers will be slower and have a higher CPU usage). If a1ide_xfer is not set then your A1's internal IDE will default to use fastest PIO mode only. To see which modes are used for your disks you can use:

idetool -l <device driver>

For the internal A1 IDE this is:

idetool -l a1ide.device

If you have good enough cables and your A1 is DMA fixed you should be able to enable UDMA on all your disks by just setting:

nvsetvar a1ide_xfer GGGG

Since G is the highest UDMA mode this means that it will use the highest mode that your disks claim to support.
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Re: what is fixed xe (g4) dma and usb hardware

Postby msalcedo » Tue Jul 30, 2013 12:25 am

@salass00
Thanks for the info. I understand (a little) now about the setting means and how to go about seeing and changing that setting.
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