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identify 486 motherboard

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Reply 21 of 49, by Tiido

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quicknick wrote:

...setting the voltage accordingly (the only jumpers documented on board are the voltage ones)...

I came in posession of this same board, with the exception of not even the voltage jumpers are documented and cache chips are fake and soldered on. Your photo shows 3 of the voltage settings but not the 4th one, can you tell me what it is ?

I'm going to remove the fake cache chips and install sockets (I heat tested one chip and it sure is normal plastic 🤣, and eventually also figure out what all the jumpers do, unless this info comes up before 🤣.

ALI486.jpg

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Reply 23 of 49, by Tiido

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BIOS ID string is 41-C101-428027-00101111-101094-ALI87/89-U
BIOS itself is here : http://www.tmeeco.eu/BitShit/PCschit/V1-HJ2.BIN
Back of the board has a text : PCI486 V1-HJ2 on it.

T-04YBSC, a new YMF71x based sound card & Official VOGONS thread about it
Newly made 4MB 60ns 30pin SIMMs ~
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Reply 24 of 49, by Deksor

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Unfortunately the manufacturer id 8027 leads to "unknown" from this source http://www.idhw.com/textual/guide/inst_mobo_ami_manu.html

So I can't give you any useful infos, except that this bios is from October 1994 so it may support LBA !

I'm quite curious to know who made this now ! This could put a name on the "8027" manufacturer name which might help other people later.

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Reply 25 of 49, by Tiido

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Yeah, it does support LBA which is pretty nice. The silkscreening (fonts and symbols etc.) looks exactly like on IO cards made by Kentech :
ALI4862.jpg

I have also figured out some of the jumpers along the way :
JP35 + JP36 : FSB speed select : 25/33/40/50. PLL is IMI SC468. If 3rd jumper is added you can get 30/60/66/80 in addition.
JP39 is PCI divider select. 1-2 is normal, 2-3 is half.

JP40 is floppy controller enable (1-2) and disable (2-3)

JP44+45 are CPU voltage select, 5V (1-2) and low voltage (2-3) and JP43 and JP42 select the low voltage with one jumper on them at a time, having multiple jumpers will allow additional voltages but they're all probably between 4 and 5V.
JP42 1-2 is 3.6V and 2-3 is 4V
JP43 1-2 is 3.3V and 2-3 is 3.45V

JP4 is reset switch
JP5 is turbo LED
JP6 is turbo switch, closed=normal, open=de-turbo
JP12 is PC speaker
JP1 should be the key-lock + power LED
JP2 and 3 in the general area are unknown for the time being.

JP7 to JP11 are IRQ selects, 3/4/5/7/9, most probably for LPT port.
QP26 and JP27 select between DMA1 (2-3) and DMA3 (1-2), most probablf ECP DMA.
JP28 and JP29 select between IRQ3 (2-3) and IRQ4 (1-2), most probably COM port IRQs.
JP30, 31 and 32 are most probably COM and LPT address selects

JP33 didn't seem to do anything on first glance
JP38 is most probably external battery + CMOS clear jumper. 1 is GND, 2-3 are jumpered for normal operation and read battery voltage on them and 4 is probably + terminal of a battery.

The easy part is now done pretty much, cache control and CPU jumpers will be a headache to figure out but with CPU pinouts available it shouldn't take tremendous effort to find out what they all do. Cache ones will likely be more effort. I can certainly figure out at least the jumpers that control if 8/32/128KB chips are used. I'll post more info as I acquire it here.

T-04YBSC, a new YMF71x based sound card & Official VOGONS thread about it
Newly made 4MB 60ns 30pin SIMMs ~
mida sa loed ? nagunii aru ei saa 😜

Reply 27 of 49, by Tiido

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Someone else can do the diagrams etc. I have now figured out the CPU and cache jumpers, or rather what they are. How exactly they need to be set I don't quite yet know, and the BIOS is not cooperating as far as cache goes. I have tried another ALI BIOS and it works as long as cache chips are removed or cache is disabled from BIOS. Register reference and pinouts exist and i began writing an util to enable L2 though without any luck as any L2 related operation crashes...

Here's the CPU jumpers and some thoughts about what few CPUs should be set to (5x86 refers to Cyrix not AMD) :
ALI486.png
I am not completely sure about JP14 (seems to force cache flush on all writes or something) and JP23 (datasheet says PCD signal on chipset is don't care in WB mode). All others seem to make sense with the exception of Cyrix stuff on JP17 and JP21.

T-04YBSC, a new YMF71x based sound card & Official VOGONS thread about it
Newly made 4MB 60ns 30pin SIMMs ~
mida sa loed ? nagunii aru ei saa 😜

Reply 28 of 49, by quicknick

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Tiido wrote:

I came in posession of this same board, with the exception of not even the voltage jumpers are documented and cache chips are fake and soldered on. Your photo shows 3 of the voltage settings but not the 4th one, can you tell me what it is ?

Hi, congrats on your work! I will be able to provide this next week if you're still interested. I'm out of the country at the moment.

Reply 29 of 49, by Deksor

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Well pay attention to the cache jumpers on your first photo, they're hardwired in some way. What I noticed was that all boards with fake cache had the fake amount of cache hardwired so in your case you have pretty much the settings for 256KB of cache.

Trying to identify old hardware ? Visit The retro web - Project's thread The Retro Web project - a stason.org/TH99 alternative

Reply 30 of 49, by Tiido

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The cache ones are all traced out too and there's essentially 3 links to connect upper address lines of the 2 banks together or directly to some pins on the chipset. I don't yet know the significance of it, but the wrong BIOS definitely recognizes that there's 256KB of cache but will crash. I'll be tracing out how the cache is connected soon. It'll be a great board once there's working cache ~

quicknick wrote:

Hi, congrats on your work! I will be able to provide this next week if you're still interested. I'm out of the country at the moment.

I have actually figured out the way the jumpers work meanwhile so there's actual need to know them anymore with the exception of seeing the actual listed voltages, since I didn't actually measure exactly 3.3V or 3.45 etc. but more in all cases.

T-04YBSC, a new YMF71x based sound card & Official VOGONS thread about it
Newly made 4MB 60ns 30pin SIMMs ~
mida sa loed ? nagunii aru ei saa 😜

Reply 31 of 49, by Tiido

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So I spent a while tracing out how the cache connects and it doesn't seem anything is actually wrong as far as connectivity goes and connections from CPU to chipset to cache seem to make sense mostly. All the boards with this chipset require size jumpers and that's where I am stumped, I don't know how the CPU address lines need to be connected to the cache address lines in each different size configuration or how is that determined, the datasheet has all software controlled size stuff with algos for BIOS writers to detect cache size and organization.

The jumper block seems to allow connecting CPU addresses to top address lines of the cache chips and also separate the top address lines of the two cache banks. There's also room for shuffling the connectivity between the top lines but it won't make sense since TAG and L2 banks connect all the same way and when data is read and written with random address organization there's no actual difference in operation. When the banks have top address lines separated the Bank1 will have them floating (!) which means instant crash in single bank config if it was working, while unconnected CPU to TAG+Bank2 addresses are properly tied to ground and will be stable and in theory work right. I'm pretty sure this board has some blunder as far as cache connection goes, which might be way the BIOS is never enabling cache even on boards with sockets and whatnot... which is really seriously dumb...

At this point I would like to get my hands on another board with this chipset (i.e temporary loan) and actually see how cache and TAG are connected on them and then replicate it on this board. It will also help if someone with multimeter and a board with working cache can trace out how the cache conf jumpers are connected and how cache itself is connected on their board to the CPU bus and the chipset.

Here's all the info I have gathered :
ALI4862.png

T-04YBSC, a new YMF71x based sound card & Official VOGONS thread about it
Newly made 4MB 60ns 30pin SIMMs ~
mida sa loed ? nagunii aru ei saa 😜

Reply 32 of 49, by Deksor

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Well I'll take a look at that bios maybe there are options that are hidden that can be shown again concerning cache ? What kind of Ami bios is that already ? Is it a winbios ?

Trying to identify old hardware ? Visit The retro web - Project's thread The Retro Web project - a stason.org/TH99 alternative

Reply 33 of 49, by Tiido

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WinBIOS yes. Using an Award BIOS from another board freezes when OS load needs to start and my own attempts at enabling L2 also result in a freeze. This is not a software issue but most certainly an hardware issue and I'm 100% certain a modification is necessary to get cache working right even when BIOS is no longer in the way.

T-04YBSC, a new YMF71x based sound card & Official VOGONS thread about it
Newly made 4MB 60ns 30pin SIMMs ~
mida sa loed ? nagunii aru ei saa 😜

Reply 34 of 49, by Deksor

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Here's my attempt at making a schematic "à la TH99" like I said earlier 😁.

I didn't label the jumpers, but everything else should be there.

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Here's the .pdn file if you want to improve it :

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Trying to identify old hardware ? Visit The retro web - Project's thread The Retro Web project - a stason.org/TH99 alternative

Reply 35 of 49, by jack7277

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Help me please to find manual, it wont start, only cpu heat, on the back there is text- Liteon 20v0 9608-11

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Reply 37 of 49, by mpe

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kalohimal wrote on 2020-06-22, 14:52:

stason.../TULARC/pc/motherboards/A/ACTION-WELL-DEVELOPMENT-LTD-486-AM-8887.html

Version that doesn't ruin your sex life:

https://th99.bl4ckb0x.de/m/A-B/35852.htm

Blog|NexGen 586|S4

Reply 39 of 49, by mkarcher

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Floppy disk(s) fail is OK if no floppy controller or floppy drive is connected.

CMOS checksum error is normal if the CMOS battery is flat.

Keyboard error or no keyboard present is expected if indeed no keyboard is connected.

"Keyboard is locked out" is not expected when you test a board, and most likely points to a problem. "Keyboard is locked out" means that the keyboard controller (either the one integrated in the UMC UM8886 south bridge, or a dedicated one) has its keylock input line at low level. This line should be pulled up by a resistor on the mainboard, and thus should be at high level unless the keylock switch pulls it to ground. If the board has no external keyboard controller, pin 4 of the keylock/power LED connector should be connected to pin 55 of the UM8886 chip. There might be a "factory reserved" jumper in the path, though. If that jumper is missing, it might explain the error message.

See Success: Adding a PS/2 mouse port to the Shuttle HOT433 (using a dedicated keyboard controller chip) for a detailed description of the keyboard interface in the UM8886 south bridge. The board I modified in that post has a zero-ohm resistor in position R30 to connect the keylock pin (with its pull-up resistor) to pin 55 of the south bridge. It is possible that your board does not use a soldered zero-ohm resistor for that purpose, but instead has a jumper.

Last edited by mkarcher on 2020-06-22, 15:48. Edited 2 times in total.