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OldTech, PCI bus trafic limitation 133 MB/s for all devices, am i right?

ruthan

ruthan

Member
Hello,
i just want to more understanding of PCI bus based computers limits.

I read years ago that whole PCI bus based computer is limited to 133 MB/s for all devices, i want to know..
1) If is true
2) Are in 133 MB/s budget included also IDE and Sata devices?
3) When i hit cap, which traffic has priority?
 
The first two is correct. The third I don't know, check Wikipedia? Now that is for PCI 32 bit 33Mhz.
 
Thanks, what about PCI 66 MHz implemetation, i dont know if it ever came to desktops?

For my is most interesting Intel 865 chipset and how it will behave.
 
ruthan said:
Thanks, what about PCI 66 MHz implemetation, i dont know if it ever came to desktops?

For my is most interesting Intel 865 chipset and how it will behave.
Click to expand...
Some Xeon workstations have it but I don't know any details. It is common in non-x86 workstations like Sun and Alpha ones.
 
ruthan said:
I read years ago that whole PCI bus based computer is limited to 133 MB/s for all devices, i want to know..
1) If is true
2) Are in 133 MB/s budget included also IDE and Sata devices?
3) When i hit cap, which traffic has priority?
Click to expand...

1) Yup.
2) Depends on the system in question. Some newer chipsets have serveral, separate PCI buses for various devices. The 865 you have is new enough to have a separate ATA/SATA controller if I remember correctly. The old hub interface for the ICH is 266MB/s far as I remember.
3) That depends on the specific implementation.
 
Thanks again.

2) How to check that chipset have more than 1 PCI Bus, is there any parameter which can be show by some HW diagnostics tools or there are some official bussword for this in the specs?
3) Its it Board of OS thing and if is OS thing, how Windows 98 and XP behave?
 
ruthan said:
2) How to check that chipset have more than 1 PCI Bus, is there any parameter which can be show by some HW diagnostics tools or there are some official bussword for this in the specs?
Click to expand...

HWiNFO should show you. You'll notice if there are multiple numbered PCI buses in the tree menu for the southbridge. Be aware some things report as PCI buses without actually being PCI.

ruthan said:
3) Its it Board of OS thing and if is OS thing, how Windows 98 and XP behave?
Click to expand...

PCI uses bus mastering, with multiple masters allowed. Its up to the BIOS to decide which gets serviced first. This happens using IRQs. In ye-olde-days you had to set this up manually, but has since become plug-and-play. So it depends on the system in question. Generally lower IRQ number = Priority. But take that with a grain of salt, also because multiple devices can use the same IRQ.

I miss Intel 8259 interrupt controllers. Things were much simpler back then... 🙁
 
This is assuming there is only one pulse per clock when in fact sometimes there are two per clock cycle. It also can have multiple pathways per rail. i.e. X16.
 
Not all IDE cables are 133. It depends on the chip set the bios settings and the Cable i.e. 80 pin EIDE Ultra 2. Plus some cables support 2 drives. I have not used one of those in a while. I would try to use a single cable for the Hard drive and put the OPTICAL drive on the second IDE cable. The dual cables were set up with a slave and master. I dont know how they decide on which one gets priority. Early optical drives did not run that fast.
 
piasabird said:
Not all IDE cables are 133. It depends on the chip set the bios settings and the Cable i.e. 80 pin EIDE Ultra 2. Plus some cables support 2 drives. I have not used one of those in a while. I would try to use a single cable for the Hard drive and put the OPTICAL drive on the second IDE cable. The dual cables were set up with a slave and master. I dont know how they decide on which one gets priority. Early optical drives did not run that fast.
Click to expand...
By a jumper on the drives. I'm glad we don't have to do that anymore.
 
Yeah i know, know.. but to be honest, i havent money in that age , so i only could dream about SCSI and or quick drives like Quantum etc, so capacity was the king..
 
ruthan said:
Yeah i know, know.. but to be honest, i havent money in that age , so i only could dream about SCSI and or quick drives like Quantum etc, so capacity was the king..
Click to expand...
I never messed with SCSI, but by the time I was upgrading and building computers PATA drives displaced SCSI drives in the consumer space.
 
I do recall some SCSI peripherals in "consumer space" such as the HP Scanjet flatbed scanner.
 
Well, I had one and was then purely a consumer. I also had SCSI external drives and a SCSI printer. As I recall that was circa 1992-95. I also recall transitioning from SCSI I, II, and III cables. Since this was before USB, it was the only way we could daisy chain hardware at that time. I guess I was an exception to your rule. 🙂
 
corkyg said:
Well, I had one and was then purely a consumer. I also had SCSI external drives and a SCSI printer. As I recall that was circa 1992-95. I also recall transitioning from SCSI I, II, and III cables. Since this was before USB, it was the only way we could daisy chain hardware at that time. I guess I was an exception to your rule. 🙂
Click to expand...
Computer geeks are not consumer...
 
I was not a computer geek back then . I had just retired. Remember Zip drives? They were basically SCSI. I had several all linked together. Just remember, all generalizations are false, including this one. 🙂
 
And corkyg is right. SCSI was in the consumer space for awhile. Apple, Atari, and Commodore all used it in their consumer level m68k systems.
 
corkyg said:
I was not a computer geek back then . I had just retired. Remember Zip drives? They were basically SCSI. I had several all linked together. Just remember, all generalizations are false, including this one. 🙂
Click to expand...


They were parallel port first.
 
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