Dan_Sarandon
Posts: 11 +0
Kind friends:
I have recently acquired an (admittedly antediluvian) Toshiba 3200 P-III 600MHz system for use as a dedicated ‘control head’ for a PIC programmer and a digital spectrum analyzer (i.e. frequency domain o’scope) (The former connected via an RS232 serial port and the latter a PCI bus slot).
As received, the system was equipped with a 40X CDR (IDE), a 10GB HDD (IDE) a 1.44 MB FDD and 256MB of SIMM RAM.
Please note that the following hardware is integral to the system board:
-IO ports (Parallel, RS232 and USB).
-Audio (i.e. "sound card") functionality.
-Video adapter.
-IDE and FDD controllers.
Leaving the bus slots (2 PCI and 1 ISA) free.
To the above I have installed (added):
-1 new 100GB HD (Glory be to Maxtor’s DDO scheme!
)
-A non self-powered USB hub (for use with ‘flash’ drives)
-The spectrum analyzer interface card.
Ok here’s the deal:
In consideration of the (physically) diminutive PSU, I thought it wise to examine the various EMFs for indication of overload (to wit: excessive voltage drops on any line) -- first via BIOS’ sensor readings then via direct measurements made during worst-case demand. – All readings were ‘better’ than nominal except the –5v supply (which floated about -0.07v)
Upon inspection I discovered that the –5V line (position #18 at the PSU- to-system board connector) was omitted – further investigation indicated that the PSU was clearly manufactured thus.
Given that the system board’s PSU connector is clearly marked “ATX Power Supply”, the -5v sensor is ‘active’, the unit contains an ISA slot (-5v position floating) it is clear to me that I’ve got hold of an ‘ATX system’ equipped with an SFX PSU.
Hence my question: So long as I do not use the ISA slot, does the omission of the –5v supply matter???
So far as I am aware, third and subsequent generation LSIs, VLSI, etc. have no requirement of external substrate bias application – which, to the best of my knowledge, is/was the sole purpose of the –5v supply???
At ‘first blush’, Owing to the miniscule current requirement (300 mA) it seems a ‘painless fix’ would be to develop the –5v supply from –12v using an LM7905 linear VR. -- Unfortunately -12 is a low-current supply itself and my application requires reliable RS232!
Many, many thanks in advance for any forthcoming insight/info
Very best regards
Dan
I have recently acquired an (admittedly antediluvian) Toshiba 3200 P-III 600MHz system for use as a dedicated ‘control head’ for a PIC programmer and a digital spectrum analyzer (i.e. frequency domain o’scope) (The former connected via an RS232 serial port and the latter a PCI bus slot).
As received, the system was equipped with a 40X CDR (IDE), a 10GB HDD (IDE) a 1.44 MB FDD and 256MB of SIMM RAM.
Please note that the following hardware is integral to the system board:
-IO ports (Parallel, RS232 and USB).
-Audio (i.e. "sound card") functionality.
-Video adapter.
-IDE and FDD controllers.
Leaving the bus slots (2 PCI and 1 ISA) free.
To the above I have installed (added):
-1 new 100GB HD (Glory be to Maxtor’s DDO scheme!
) -A non self-powered USB hub (for use with ‘flash’ drives)
-The spectrum analyzer interface card.
Ok here’s the deal:
In consideration of the (physically) diminutive PSU, I thought it wise to examine the various EMFs for indication of overload (to wit: excessive voltage drops on any line) -- first via BIOS’ sensor readings then via direct measurements made during worst-case demand. – All readings were ‘better’ than nominal except the –5v supply (which floated about -0.07v)
Upon inspection I discovered that the –5V line (position #18 at the PSU- to-system board connector) was omitted – further investigation indicated that the PSU was clearly manufactured thus.
Given that the system board’s PSU connector is clearly marked “ATX Power Supply”, the -5v sensor is ‘active’, the unit contains an ISA slot (-5v position floating) it is clear to me that I’ve got hold of an ‘ATX system’ equipped with an SFX PSU.
Hence my question: So long as I do not use the ISA slot, does the omission of the –5v supply matter???
So far as I am aware, third and subsequent generation LSIs, VLSI, etc. have no requirement of external substrate bias application – which, to the best of my knowledge, is/was the sole purpose of the –5v supply???
At ‘first blush’, Owing to the miniscule current requirement (300 mA) it seems a ‘painless fix’ would be to develop the –5v supply from –12v using an LM7905 linear VR. -- Unfortunately -12 is a low-current supply itself and my application requires reliable RS232!
Many, many thanks in advance for any forthcoming insight/info
Very best regards
Dan
