What part or peripheral on mobo requires -5V?

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What part or peripheral on mobo requires -5V?

Postposted on Mon May 14, 2012 7:07 pm

I need to replace a psu which has -5V output. I heard or read somewhere that ISA uses it. If that is the case then I can use one without it because no ISA card is populated on the motherboard. Could anyone enlighten me on the above?
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Re: What part or peripheral on mobo requires -5V?

Postposted on Mon May 14, 2012 7:23 pm

IIRC it was ISA and floppy drives. Also, some soundcards and some fancy equipment require a floppy drive power connector.
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Re: What part or peripheral on mobo requires -5V?

Postposted on Mon May 14, 2012 7:45 pm

Just ISA peripherals. Floppy connectors use +5V and +12V.

-5V does not appear in modern power supplies, no doubt because ISA slots no longer exist except for specialized machines.
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Re: What part or peripheral on mobo requires -5V?

Postposted on Mon May 14, 2012 7:58 pm

bthylafh wrote:Just ISA peripherals. Floppy connectors use +5V and +12V.

-5V does not appear in modern power supplies, no doubt because ISA slots no longer exist except for specialized machines.

Thanks for your help. That gives me lot more freedom because psu with -5V is hard to come by nowadays.
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Re: What part or peripheral on mobo requires -5V?

Postposted on Mon May 14, 2012 8:00 pm

morphine wrote:IIRC it was ISA and floppy drives. Also, some soundcards and some fancy equipment require a floppy drive power connector.

There's nothing with -5v in any 4-pin connector (Molex or Berg). It's just +5v,+12v, and a pair of ground connections.
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Re: What part or peripheral on mobo requires -5V?

Postposted on Mon May 14, 2012 9:27 pm

Old types of memory. Very old. Early ISA bus old.
A/D converters, not of types found in typical PC's. If a peripheral did need -5V, it would be trivial to put a DC-DC converter on the board. I've used instrumentation cards that have an A/D with -5V to 5V range, which would require -5V power rail for reference. That's not something a typical PC will have.
Frankly, nothing in a typical modern PC uses -5V.
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Re: What part or peripheral on mobo requires -5V?

Postposted on Mon May 14, 2012 10:33 pm

The last time I saw -5V wired on a power supply it was a JAMMA standard one in a late-80's arcade cabinet. The sound on the board wouldn't work when replaced with an ATX power supply that didn't have -5V. Like mnecaise says, I really doubt you can find any contemporary PC equipment that needs to draw -5VDC for any reason.
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Re: What part or peripheral on mobo requires -5V?

Postposted on Tue May 15, 2012 6:47 am

derFunkenstein wrote:
morphine wrote:IIRC it was ISA and floppy drives. Also, some soundcards and some fancy equipment require a floppy drive power connector.

There's nothing with -5v in any 4-pin connector (Molex or Berg). It's just +5v,+12v, and a pair of ground connections.

You're right, of course. Didn't immediately realize we were talking minus 5V.
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Re: What part or peripheral on mobo requires -5V?

Postposted on Tue May 15, 2012 7:07 am

Some older COM ports may have used it, as the RS-232 standard specifies a symmetrical (about ground) voltage swing of +/- 3 to 15 volts. Modern RS-232 transceivers just use an on-chip charge pump to internally generate the required negative rail (and these days most people use USB-to-RS-232 dongles instead of native COM ports anyway).

I recall reading a few years back that onboard audio on some motherboards with integrated Creative codecs wouldn't work if your PSU lacked a -5V rail. Fortunately (in multiple ways) integrated Creative codecs are rare to non-existent these days.
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Re: What part or peripheral on mobo requires -5V?

Postposted on Tue May 15, 2012 8:57 am

The motherboard to be powered by the psu in question is the following:
http://www.gigabyte.com/products/product-page.aspx?pid=1433&dl=1#sp
It has ISA, RS232 and integrated Creative CT5880. I do not use none of these, but have to use Sound Blaster PCI 128 card(ES1373). Does this sound card require minus 5V?
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Re: What part or peripheral on mobo requires -5V?

Postposted on Tue May 15, 2012 9:43 am

It is possible a motherboard that old may not function properly without the -5V. Another potential issue is that this motherboard is likely from before the emphasis shifted from having most of the wattage on the +3.3V/+5V rails to the +12V rail; the +3.3V/+5V rails on a new PSU may not have sufficient wattage.

IMO your best bet is to find a secondhand PSU of similar age to the motherboard.
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Re: What part or peripheral on mobo requires -5V?

Postposted on Tue May 15, 2012 10:35 am

just brew it! wrote:It is possible a motherboard that old may not function properly without the -5V. Another potential issue is that this motherboard is likely from before the emphasis shifted from having most of the wattage on the +3.3V/+5V rails to the +12V rail; the +3.3V/+5V rails on a new PSU may not have sufficient wattage.

IMO your best bet is to find a secondhand PSU of similar age to the motherboard.

I have another mobo of the same model and spec of the psu which comes with it is as follows:
+3.3V/14A
+5V/21A
+12V/7A
-5V/0.3A
-12V/0.5A
+5Vsb/0.8A
It is possible to find a psu with the above current ratings for +3.3V and +5V even it does not have -5V output.
I got one with -5V from a internet reseller but it died after several hours' use. Question is whether to get the same model replacement or a different model. A different model means no -5V because the one I have now is the only model which is available from that vendor. I'd rather get a different model because the present one is very noisy.
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Re: What part or peripheral on mobo requires -5V?

Postposted on Wed May 16, 2012 4:27 pm

Socket 370 isn't exactly the dark ages of computing. It should work just fine with any modern powersupply (you'll just need to detach the four [4] extra pins on the main power connection).

Now with that said, old VIA chipsets generally make me want to vomit.
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Re: What part or peripheral on mobo requires -5V?

Postposted on Wed May 16, 2012 6:10 pm

Egglick wrote:Socket 370 isn't exactly the dark ages of computing. It should work just fine with any modern powersupply (you'll just need to detach the four [4] extra pins on the main power connection).

I do not think -5V is carried in that extra four pins. The main power cable used to be 20pins even before -5V was dropped.

Now with that said, old VIA chipsets generally make me want to vomit.

Could you explain why? I got this mobo from eBay to see Windows 95 operating naitively. Is there any other legacy mobo for this purpose which you recommend?
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Re: What part or peripheral on mobo requires -5V?

Postposted on Wed May 16, 2012 6:32 pm

churin wrote:
Now with that said, old VIA chipsets generally make me want to vomit.

Could you explain why? I got this mobo from eBay to see Windows 95 operating naitively. Is there any other legacy mobo for this purpose which you recommend?

Most VIA boards from that era were perfectly fine, the problem was that VIA didn't always supply adequate documentation to the board vendors who, in turn, had trouble choosing the correct default settings BIOS software. That noted:

1) Make sure the board has the most recent BIOS version you can locate.

2) Look for an entry, probably in a "Chipset Features Setup" menu, labeled "Multi-level I/O queue" or similar. Set it to the highest number. Lower numbers were only there for compatibility checks, and tend to choke the communications channel between the northbridge and the southbridge. IIRC the highest setting is "5" but "3" and "1" are usually available and sometimes enabled as the default setting.

3) Creative soundcards sometimes hogged the PCI bus in a way that was actually a violation of the PCI spec, but stable on all Intel chipsets. If the onboard sound or any external Creative soundcard is plagued by static or glitching, look for the "PCI Latency Timer" and change it from the default 32 cycles to 64 cycles, and if that still doesn't fix it, try 128 cycles.
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Re: What part or peripheral on mobo requires -5V?

Postposted on Wed May 16, 2012 7:15 pm

ludi wrote:2) Look for an entry, probably in a "Chipset Features Setup" menu, labeled "Multi-level I/O queue" or similar. Set it to the highest number. Lower numbers were only there for compatibility checks, and tend to choke the communications channel between the northbridge and the southbridge. IIRC the highest setting is "5" but "3" and "1" are usually available and sometimes enabled as the default setting.

I reviewed the "Chipset Features Setup" but could not find where to do the above.
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Re: What part or peripheral on mobo requires -5V?

Postposted on Wed May 16, 2012 7:29 pm

churin wrote:
Egglick wrote:Socket 370 isn't exactly the dark ages of computing. It should work just fine with any modern powersupply (you'll just need to detach the four [4] extra pins on the main power connection).

I do not think -5V is carried in that extra four pins. The main power cable used to be 20pins even before -5V was dropped.

Correct. The extra 4 pins provide an additional +12V, +5V, +3.3V, and Ground line, to reduce resistive losses. The pin which was originally used for -5V is defined as "Reserved" in the current ATX PSU spec.
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Re: What part or peripheral on mobo requires -5V?

Postposted on Wed May 16, 2012 7:30 pm

churin wrote:I reviewed the "Chipset Features Setup" but could not find where to do the above.

Not all motherboards let you set it.
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Re: What part or peripheral on mobo requires -5V?

Postposted on Wed May 16, 2012 7:36 pm

ludi wrote:
churin wrote:
Now with that said, old VIA chipsets generally make me want to vomit.

Could you explain why? I got this mobo from eBay to see Windows 95 operating naitively. Is there any other legacy mobo for this purpose which you recommend?

Most VIA boards from that era were perfectly fine, the problem was that VIA didn't always supply adequate documentation to the board vendors who, in turn, had trouble choosing the correct default settings BIOS software. That noted:

1) Make sure the board has the most recent BIOS version you can locate.

2) Look for an entry, probably in a "Chipset Features Setup" menu, labeled "Multi-level I/O queue" or similar. Set it to the highest number. Lower numbers were only there for compatibility checks, and tend to choke the communications channel between the northbridge and the southbridge. IIRC the highest setting is "5" but "3" and "1" are usually available and sometimes enabled as the default setting.

3) Creative soundcards sometimes hogged the PCI bus in a way that was actually a violation of the PCI spec, but stable on all Intel chipsets. If the onboard sound or any external Creative soundcard is plagued by static or glitching, look for the "PCI Latency Timer" and change it from the default 32 cycles to 64 cycles, and if that still doesn't fix it, try 128 cycles.


I think VIA's problems stemmed more from their drivers than anything. They were extremely buggy (causing bluescreens and crashes), and it was very difficult to find the correct version (simply going with the latest "4-in-1's" often wouldn't cut it). Especially with an Intel CPU, VIA chipsets were considered "budget boards", which meant they also got paired with lower-end components and circuitry. Most of my experience with VIA came from running AMD cpus before Nvidia's nForce line came out. I pretty much abandoned them after that.

Anyhow, if you're just screwing around, I wouldn't fret over it too much.
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Re: What part or peripheral on mobo requires -5V?

Postposted on Thu May 17, 2012 8:34 am

Egglick wrote:I think VIA's problems stemmed more from their drivers than anything. They were extremely buggy (causing bluescreens and crashes), and it was very difficult to find the correct version (simply going with the latest "4-in-1's" often wouldn't cut it). Especially with an Intel CPU, VIA chipsets were considered "budget boards", which meant they also got paired with lower-end components and circuitry. Most of my experience with VIA came from running AMD cpus before Nvidia's nForce line came out. I pretty much abandoned them after that.

Could anyone provide name of the NVidia's chipsets for P3 1GHz, or better yet a specific legacy mobo using this chipsets?
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Re: What part or peripheral on mobo requires -5V?

Postposted on Thu May 17, 2012 8:51 am

In those days Nvidia only made chipsets for the AMD Athlon/Duron series. Those were the Nforce and Nforce 2.

The trick, IME, to getting a Via board to work right was to visit Via's driver site and on the 4-in-1 section it would tell you which chipset worked best with the newest version and which worked best with an older unmaintained branch; probably your board is old enough that it'd want the latter. Also as noted, don't use a Creative-based sound card.

I had a Via Apollo Pro 133A-based Socket-370 board [1] and it was rock solid for me... of course, most of the time I had that board it was running Debian Linux (and briefly WinXP), so my experience might not directly apply.


[1] Tyan Trinity 400. It also had a Slot-1 so you could use older P2 and P3 processors, but was /not/ SMP-capable. IIRC its CPU support topped out at around an 833 MHz Pentium III.
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Re: What part or peripheral on mobo requires -5V?

Postposted on Thu May 17, 2012 8:59 am

On the AMD side, VIA's KT880 was a very good chipset for Socket-A, but folks had all moved on to NForce2 by that point.

You must have a very specific requirement to try to keep a socket-370 system running these days.
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Re: What part or peripheral on mobo requires -5V?

Postposted on Thu May 17, 2012 9:06 am

churin wrote:Could anyone provide name of the NVidia's chipsets for P3 1GHz, or better yet a specific legacy mobo using this chipsets?


The Intel 815 chipset series or certain high end Intel 440BX motherboards would be the best in terms of chipset support from that era.

Problem is that timeframe also represents the height of the capacitor plague. Anything you buy from those days is a walking timebomb.

You really should virtualize Windows 95. There's nothing to gain from a native install except headaches.
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Re: What part or peripheral on mobo requires -5V?

Postposted on Thu May 17, 2012 9:11 am

Ryu Connor wrote:Problem is that timeframe also represents the height of the capacitor plague. Anything you buy from those days is a walking timebomb.

Anything you buy from those days that still functions probably wasn't affected by the plague, unless it is "new old stock".
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Re: What part or peripheral on mobo requires -5V?

Postposted on Thu May 17, 2012 9:14 am

$200 would get you a modern CPU w/ IGP + motherboard w/ USB3 + 4 GiB of DDR3 memory.

If you must look for ancient hardware, one of the Intel i815 chipset variants would be the best option for a processor of that era.
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Re: What part or peripheral on mobo requires -5V?

Postposted on Thu May 17, 2012 9:22 am

JustAnEngineer wrote:$200 would get you a modern CPU w/ IGP + motherboard w/ USB3 + 4 GiB of DDR3 memory.


His purpose is to get the Windows 95 experience, so unless he wants to virtualize that won't help him much.

If you must look for ancient hardware, one of the Intel i815 chipset variants would be the best option for a processor of that era.


That said, yes, an 815e-based board is a good choice for running Win9x (I'd really go for 98SE if I were you) on hardware if you already have a 1 GHz P3 CPU.
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Re: What part or peripheral on mobo requires -5V?

Postposted on Thu May 17, 2012 9:34 am

just brew it! wrote:
Ryu Connor wrote:Problem is that timeframe also represents the height of the capacitor plague. Anything you buy from those days is a walking timebomb.

Anything you buy from those days that still functions probably wasn't affected by the plague, unless it is "new old stock".


Can't really rule out light use. Also many vendors accepted RMA's on the bad boards and simply sent along a refurb or factory fresh board with the exact same brand of faulty capacitors. These replacement boards introduce a new crinkle in when and how long they may have been used before retired.
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Re: What part or peripheral on mobo requires -5V?

Postposted on Thu May 17, 2012 10:18 am

I agree that the Intel 815 chipset is going to be the best choice for a Socket 370. The slightly older 440BX chipset was rock solid as well, but I don't know if it went beyond Slot 1. Just make sure you don't buy an 820 (it had a serious, uncorrectable bug).

Like I said earlier though, if you're just screwing around there's no point spending more money. Just see how the VIA goes.
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Re: What part or peripheral on mobo requires -5V?

Postposted on Thu May 17, 2012 2:38 pm

Egglick wrote:The slightly older 440BX chipset was rock solid as well, but I don't know if it went beyond Slot 1.
A slocket would fix that though. I just finallly got rid of my Celeron 566A overclocked to 850Mhz on a slocket on an Abit BF6 last weekend.
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Re: What part or peripheral on mobo requires -5V?

Postposted on Thu May 17, 2012 3:25 pm

notfred wrote:
Egglick wrote:The slightly older 440BX chipset was rock solid as well, but I don't know if it went beyond Slot 1.
A slocket would fix that though. I just finallly got rid of my Celeron 566A overclocked to 850Mhz on a slocket on an Abit BF6 last weekend.


Yeah, I used one of those in a system or two. I haven't seen one in almost 10 years though. I wouldn't think an old Celeron would be worth the trouble nowadays.
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