Re: Asus P2B-DS Rev 1.06 FSB Modification
Posted on 2020-11-14, 23:32
I don't have that motherboard, but it's not hard to imagine how it would look like 😉
Re: How to slow down NEC V20?
Posted on 2020-11-14, 23:24
Jake basically has provided the solution to your timer problem, I had modified BIOS a bit differently (no NOPs). There are 3 modified BIOS images attached in the zip file, each image has some or all error subroutine calls omitted + checksums are patched. I can post the offending PIT1 testing routine …
Re: 386DX-33 Help! Mouse stopped working
Posted on 2020-11-13, 09:05
This "serial mouse doesn't work or stopped working" problem comes up regularly on VOGONS and the culprit is always the same - either missing or too low one of the two +12/-12V voltages in the ISA slots. Measure them and check corresponding AT power connector pins for corrosion or look for shunting/ …
Re: How to slow down NEC V20?
Posted on 2020-11-13, 07:50
Jo22 wrote on 2020-11-13, 06:04: Maybe it would be possible to install two CPUs (8088/V20) on a little card and switch between via a set of switches ? That would just reset the system in the best case scenario. Upload your MBs BIOS image, I'll try to track back what part of it is responsible for …
Re: How to slow down NEC V20?
Posted on 2020-11-13, 05:47
Would it be somehow possible, for example, to feed the V20 with a separate, slower clock signal? Maybe by using an interposer board with another crystal oscillator? I don't see why not, but that would make the whole idea of using a faster V20 CPU kind of pointless? Right now you can either test …
Re: Asus P2B-DS Rev 1.06 FSB Modification
Posted on 2020-11-13, 05:07
You can simplify this modification drastically. What you essentially need is just a single pull-up resistor and an optional switch to disconnect it. PLL's FS3 pin already has an internal pull-down resistor of 240K, so an additional option for pin's pull-down would be redundant. I'd recommend you to …
Re: Fixing eMachines Case
Posted on 2020-11-10, 08:30
The closing mechanism of this bay cover probably is implemented differently, but perhaps it'll give you some ideas. Filename 1.jpg File size 695.73 KiB Views 558 views Filename 2.jpg File size 635.6 KiB Views 558 views
Re: Market value for popular or rare classic computer hardware
Posted on 2020-11-08, 19:19
I recently sold a 386 DX-40, 16meg ram, 340meg hard disk, CT1740 SB16, diamond Et4000AX tower for $370AUD delivered or about $250USD. I'm starting to think I'll regret that sale as it's not really that expensive for a quality retro PC. Especially when you see how much individual parts can go for …
Re: Retro confessions. What are yours?
Posted on 2020-11-08, 18:30
I had not made a single penny from selling modern or old PC hardware, everything either was traded for something else, given away or kept for parts. Completed the first Diablo for over 200 times, at one point I could recite every text or speech from the dungeon by heart. Diablo II is a piece of …
Re: Olivetti M290s
Posted on 2020-10-27, 17:02
I would not be surprised, a bad DRAM IC is much more common, than a bad CPU. If you have 8x 4 bit wide DRAM ICs onboard (soldered?), it would mean that there are two memory banks used (BANK0 and BANK1). If you get the "failure in the first 64K of RAM" error, it means that either you have a common …
Re: Desperate BGA reball repair on Riva 128 and Geforce 2 GTS
Posted on 2020-10-26, 19:57
I don't want to be a party pooper, but if you had heated those BGA chips above 250*C for a prolonged period of time (let alone 400*C !), it can be safely assumed that they are both dead :( Read this doc., melting temperature for leaded alloy is 183*C and for lead free it's 222*C. In general, you …
Re: Buy a Tseng ET4000AX or a Cirrus Logic GD 5422?
Posted on 2020-10-26, 10:03
If I were in your place, I would replace that motherboard for a VLB one, at least and the reason for that is very simple - a forever bad performance in DOOM with no way of future improvement. Besides, those ISA cards are way overpriced.
Re: Olivetti M290s
Posted on 2020-10-26, 09:38
Doubt it, it's more likely that some general instability or diag. incompatibility with MB cause that error, it will be more clear what's happening when you'll test known good BIOS images. In the mean time, make a good visual inspection of every trace, expansion slot, chipset pin, logic IC and …
Re: Olivetti M290s
Posted on 2020-10-25, 23:37
The chip set set right pins to HIGH but since the rom is smaller, the pin 15 don't count? How it's the address sent to the Rom? A15 to A4 = 1 and A3 to A0=0? In that case if a smaller rom get the same address it will be 7FF0, A14 to A4 =1 and A3 to A0 = 0? If yes i think i see a finally a little of …
Re: Olivetti M290s
Posted on 2020-10-25, 16:29
For the diagnostic ROMs you can use the 27256 series chips (32KB) if you happen to have them, it's important to double the image size only if you have twice as large ROM chip. The idea is that image must be at the very bottom of the larger capacity ROM chip, because the first 16 bytes that x86 CPU …
Re: Olivetti M290s
Posted on 2020-10-24, 22:09
From "https://www.vogons.org/viewtopic.php?f=46&t=77291" post (don't split the thread please, it makes difficult to track your progress). Hello, i'm trying to understand how a bios parted in 2 chips is used by the CPU. I'm trying to disassembly a bios to understand some post codes sent to the LPT1 ( …
Re: Olivetti M290s
Posted on 2020-10-22, 21:55
If the RESET signal is constantly HIGH, you won't get any signs of life from that motherboard, CPU is simply not fetching and executing any instructions from BIOS. You should check +5V Power Good (PG) signal coming from the PSU and all traces/circuitry related to it, as too low or absent PG will …
Re: What are your favorite in-game soundtracks (arcade, PC, NES)?
Posted on 2020-02-04, 17:33
My list of favorite game soundtracks would be neverendless, so I'll post just one example 😉 Rob Hubbard - Skate or Die intro: NES/C64/Rearranged tune
Re: NEC Proserva V Plus (dual socket 7 system) (have a lead on multiple of these)
Posted on 2020-01-24, 00:22
Found one S5 intel motherboard with recovery jumper on it. The recovery mode is invoked by connecting address 16 line directly to the Flash ROM (MB used to have i28F001 IC), in normal mode address 16 line is inverted by 74HCT14 hex inverter (pin 9in, pin8 out). Check how 3 highest address lines are …
Re: NEC Proserva V Plus (dual socket 7 system) (have a lead on multiple of these)
Posted on 2020-01-23, 22:43
On other motherboards, which have a BIOS recovery jumper, do you know what the jumper is triggering? Perhaps I should try to trace this out on the Pentium Pro board? Does the jumper disconnect address A0 as you alluded to in PM? It would be pretty difficult to disconnect just one of the EEPROM pins …
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