Re: -5v rail on ATX PSUs

Posted on 2020-06-16, 09:25

by

by mpe

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

You can also use a modern ATX PSU and create -5V from -12V line by using a simple voltage regulator. The power draw is small on negative lines. I've done at least once. Might be easier than dealing with old PSUs.

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Re: -5v rail on ATX PSUs

Posted on 2020-06-16, 09:14

by

by mpe

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

No. It is fine. Early ATX PSUs do have -5V and they work fine as soon as your AT to ATX adaptor has a wire for it.

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Re: Why do ISA IDE controllers/HBAs only support PIO, and not DMA?

Posted on 2020-06-16, 07:15

by

by mpe

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

There are two relevant types of DMA. Classical PC-XT style "ISA" DMA and "PCI" bus-mastering DMA. ISA DMA is horribly inefficient. DMA clock is typically 4.77 MHz and has several limitations which make it unsuitable for hard-disks. IBM-XT actually used DMA for its ST-506/MFM disk interface. However, …

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Re: Bought these (retro) hardware today

Posted on 2020-06-15, 20:32

by

by mpe

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Yes. The Promise VLB controller and the Turtle Beach sound card are probably winners there...

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Re: Bought these (retro) hardware today

Posted on 2020-06-15, 14:12

by

by mpe

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

No. There is no difference in DOS. In fact there is even only a little difference in Windows unless you use very high resolution/colour depth/refresh rates for which neither Trio64 nor 32 is practical due to slow RAMDAC.

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Re: Bought these (retro) hardware today

Posted on 2020-06-15, 13:30

by

by mpe

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Diamond Stealth Trio32 & Trio64. Nothing special, just wanted to get those while still cheap...

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Re: performance of isa16bit ide controllers

Posted on 2020-06-13, 18:48

by

by mpe

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Before 1994 those were not controllers, but adaptors. The controller was on the disk and the adaptor was a simple device to connect a disk to the ISA bus. The chip plays no role in performance. There was actually a handful of ISA EIDE controllers, but they are very rare and they won't get any …

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Re: NexGen BIOS image collection

Posted on 2020-06-12, 17:19

by

by mpe

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

This will be a short thread 😀 All known BIOS versions are here - https://www.memotech.franken.de/NexGen/Bios.html

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Re: which 486 cpu pin is connected/talks to the cmos

Posted on 2020-06-12, 14:47

by

by mpe

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Perhaps describe the "CMOS register error" you see and how does it manifest. If CPU data or address bus were broken the computer wouldn't be doing anything at all (not even beep) as it wouldn't be able to execute the BIOS code and know it has to beep :) The CPU bus is connected via northbridge to …

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Re: which 486 cpu pin is connected/talks to the cmos

Posted on 2020-06-12, 13:44

by

by mpe

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

There are no such dedicated pins on the CPU. BIOS ROM CMOS NVRAM are devices that are mapped to I/O port and memory ranges and the CPU communicates with them using a general-purpose system bus just like with other devices on the motherboard. Upon start, the CPU wakes up in real mode and begins …

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Re: Looking for socket 7 motherboard info

Posted on 2020-06-10, 20:14

by

by mpe

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

It was a low-cost manufacturer always competing at the bottom end. They had a bad reputation for using false marketing, counterfeit components or cheapest parts possible, thin PCBs, etc. That resulted in high defect rates of many products lines. If they could save $0.01 on anything they've done it. …

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Re: Looking for socket 7 motherboard info

Posted on 2020-06-10, 18:48

by

by mpe

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

It is PC Chips. Likely a revision of M535 or M549. BIOS string would confirm that.

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Re: Nexgen VLB questions

Posted on 2020-06-09, 22:53

by

by mpe

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Not sure if you can upgrade the cache. It is soldered on the mb and there are solder pads for bigger chips so in theory, yes, but I thought the L2 cache on NexGen is 4-way associative rather than direct-mapped so upgrade past 256kB shouldn't be necessary...

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Re: Controller scis or not? multiple systems ...

Posted on 2020-06-09, 22:41

by

by mpe

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I was referring to local-bus IDE (PCI or VLB) on 1993/1994 motherboards. There were several problems: 1. On early PCI boards, it was widespread use of CMD640 / RZ1000 controllers which had several data corruption bugs. 2. On VL-Bus the clock of the timing (the duration of transfer pulses) is derived …

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Re: Nexgen VLB questions

Posted on 2020-06-09, 21:52

by

by mpe

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I have a few questions which couldn't find clear infos. 1) P90 runs with FSB 42MHz. Is possible to run stable with higher cpus (for example with P100?) Which VLB cards can handle ~50MHz ? Yes. The Nx586 P100 runs at 93 MHz and the board does support it. That produces VL-Bus at 46.5 MHz which is …

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Re: Controller scis or not? multiple systems ...

Posted on 2020-06-08, 21:42

by

by mpe

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

With XT systems this might be relevant, but on 386-Pentium it's not an issue. The main reason SCSI drives were faster was that the tended to spin faster which gave them faster seek times. In fact 'intelligent' controllers tended to add latency Before Pentium/Triton bus-master DMA wasn't a thing on …

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Re: Fake painted Pentium CPUs

Posted on 2020-06-08, 19:49

by

by mpe

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Yes. It is tricky to consider Pentium CPUs as being of "Socket 5" or "Socket 7" type as socket standards are separate from CPU requirements. When Intel say "the P120 has been designed for Socket 5 and P133 for Socket 7", they say so because they know that that a motherboard that adheres to Socket 7 …

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Re: Controller scis or not? multiple systems ...

Posted on 2020-06-08, 13:30

by

by mpe

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I exclusively use SCSI for my retro systems. The main advantage is that the SCSI controller comes with own BIOS so that I can bypass any size/compatibility issues of many motherboards. I can boot even on systems with dead CMOS battery that doesn't remember hard disk settings. No need to remember …

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Re: Bought these (retro) hardware today

Posted on 2020-06-08, 13:17

by

by mpe

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Opti Local Bus VGA card:

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Re: Reasonably priced VLB card

Posted on 2020-06-08, 12:29

by

by mpe

in Marvin \ Video

in Marvin \ Video

My slight preference for S3 805 is that given a plethora of Trident chips variants you could get a bad apple (as some are passive cards without acceleration if you care about that). TGUI944x should be fine though. I doubt any Trident is much faster in DOS than average S3 805 given by tiny …

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