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Yet another Opti 495SLC clone

M

mediasponge

Experienced Member
Joined
Sep 6, 2018
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147
Location
Milpitas, CA
One of the oldies I have lying around is an off brand clone EasyData ED212. (No relation to the ED-209!) :rolleyes: It has a MB with the OPTi 82C495SLC chipset, like a lot of others. This one is apparently not listed anywhere (VOGONS, elhvb). It's not a 495SX. The physical configuration of the board is different than a lot of the other similar ones. This one has 3 VLB slots at the far end of the MB, only one CPU socket for PGA, and no socket for FPU/NPU. The AMI BIOS string is 40-040A-001379-00101111-111192-OP495SLC-F. The 1379 would indicate a Win Technologies MB. It currently has a Cyrix CX486DX2V66 in it along with 16MB Ram (8 SIMM slots), a set of cache Rams, a mono/printer card, an Everex MFM controller, ST-225 disk and a 5.25 floppy. I have no manual for the MB but fortunately, on this one, the jumper settings are printed on the MB. The MB says it is a 495SLC Rev T.2.

20181009_182606.sm1.jpg 20181009_191835.sm1.jpg
 
So, I'm looking to do a retro build on this thing. Why build if it's already built, you ask? Well, the monochrome monitor is bleah, the ST-225 HDD is old, slow, and maybe dying, and it has no other redeeming qualities or features. It's also on DOS 3.1, which is way too old. I have a Hercules Dynamite Power VL card that works I can put in it, I have a real Sound Blaster card too. I plan to get one of the XT-IDE cards and run it with a real hard drive (mostly because I have tons of them). I have some questions for the collective wisdom of the group, tho:

It looks like the XT-IDE card does not provide floppy support, correct? What do folks with ISA systems do for floppy support? I can leave the old MFM controller in it, but is there an alternative? The MB has no on board controllers, and all slots are ISA or ISA/VLB.

What OS should I run? This may be answered by what games I plan to run, but basically, the choices are a later version of DOS, up to 6.22, Win 3.1, or WIN 98/98SE. I was on Win 3.1 long after 95 came out, and I was on 98SE long after XP was out. I guess unless there's a game that forces me to run 95/98, I can stay on Win 3.1 with DOS 6.22 to have the best of both for games specific to either.
 
XT-IDE is 8BIT ISA and is intended for 8086/8088 systems.

This is a VLB MOBO so a VLB I/O controller PCB is best. It will have IDE, FDD, LPT, game and 2X COM on it.

The same goes for VGA: pop in a VLB VGA PCB for best performance. 8BIT MDA/HGA/EGA/CGA is intended for 8BIT ISA 8086/8088 systems as well.

You can install Windows 98 and have it boot to DOS only (and run the Windows GUI when needed). Or MS-DOS 6.22 with Windows 3.11 of course.

You could sell your monochrome monitor and card to pay for the VLB stuff. People who are into 8086/8088 really like those old CRTs and dito cards.

I would also pop in a 3.5" DS/HD FDD and potentially sell the 5.25" DS/DD?HD? FDD. The latter have more value than the 3.5" DS/HD variety.

You may want to preventatively remove the barrel battery to avoid any future leaking.
 
PeterNC said:
XT-IDE is 8BIT ISA and is intended for 8086/8088 systems.

This is a VLB MOBO so a VLB I/O controller PCB is best. It will have IDE, FDD, LPT, game and 2X COM on it.

The same goes for VGA: pop in a VLB VGA PCB for best performance. 8BIT MDA/HGA/EGA/CGA is intended for 8BIT ISA 8086/8088 systems as well.

You can install Windows 98 and have it boot to DOS only (and run the Windows GUI when needed). Or MS-DOS 6.22 with Windows 3.11 of course.

You could sell your monochrome monitor and card to pay for the VLB stuff. People who are into 8086/8088 really like those old CRTs and dito cards.

I would also pop in a 3.5" DS/HD FDD and potentially sell the 5.25" DS/DD?HD? FDD. The latter have more value than the 3.5" DS/HD variety.

You may want to preventatively remove the barrel battery to avoid any future leaking.
Click to expand...

The Hercules VGA card I have is VLB. A VLB multifunction IO card would be great, good idea. The MB does have a socket for an external battery. I checked the existing battery and it still has good voltage on it. I do have an identical spare still in the package. The monochrome monitor is only 13" tho. And the orange text color is truly hideous! :rolleyes:
 
A lot of people like hideous amber MDA/HGA for authenticity on a 8086/8088. 5151s are very popular for 515*s.

Voltage is not so much the issue with barrel batteries. Sudden leaks and destruction of MOBOs is.
 
New issue: I can't get this thing to work with a 1.44MB 3.5" floppy drive. I tried 3 known good drives, 3 known good disks, two different controller cards, 2 or 3 different cables, but no dice. When I try to dir b: I get gibberish and speaker noises on the screen. I set the BIOS to tell it there was a 1.2MB 5.25 a: and a 1.44MB 3.5 b:, but only the 5.25 works. I also swapped a and b in the BIOS and on the cable to no avail. It may be that the BIOS is corrupted since I literally swapped everything else out with known good parts. If I can't get a decent floppy drive in it, I might abandon the project...
 
It turns out that the Opti 495SLC mobo is not the original one that came in the EasyData ED212. The original was a 286-12 mobo that I had in a box. I used that board to verify that the 3.5 drive, controller, media and cable were all good. The Opti mobo just won't deal with the 3.5 drive. What could the problem be? I've literally swapped out everything that might cause a problem, except the ram and cache. I'm not getting any memory errors.

The Opti mobo does have several jumpers on it that are not documented by being printed on the board, but the BIOS should be able to work with a 1.44MB 3.5 drive if I tell it it's got one. Very frustrating. I still suspect the BIOS. Would any Opti 495SLC BIOS work if I flash it?
 
No idea. Could be a controller bad chip. Could be a bad BIOS chip. Could be a jumper setting.
 
Another data point: Basic doesn't run on this system either. Invoke BASIC or BASICA on a DOS 3.1 system, and you get a menu for which function keys to use to load or run a basic program. This system sits there for a while, apparently frozen, then comes back with Divide Error, and the DOS prompt. I swapped CPUs at one point, same result.
 
BASIC/BASICA require ROM BASIC to be present. You need to run GWBASIC or QBASIC.
 
Can I borrow the communal "Kick Me" sign? I've been thrashing around trying to get a 1.44MB floppy to work in a DOS 3.1 system. DOS did not support 1.44MB till version 3.3! ARGH! :oops: After an install of DOS 5.0, all is well. The good news is that now the overall plan is back on track. I have a VL bus IDE/IO card on order. I already have a VLB video card and ISA sound card. Now hopefully, I can have some FUN with it instead of torturing myself...

DOS 5.0 came with QBASIC, so that solves that problem too.
 
Yep. Early DOS versions are very limited. I installed OEM MS-DOS on a Philips 286 today. No DELTREE, MEMMAMER and so on. :(
 
Now, it looks like I hit the dreaded 1024 cylinder BIOS limitation. :( I got a VLB IDE card, it works, but I can't even get a 2GB partition on a 6GB drive. The actual CHS are 13328-15-63. The BIOS lets me enter those numbers and tells me the resulting size is 6150MB, but DOS 5 Fdisk says the entire disk is 472.5 MB. The numbers 1024-16-63 give that resulting size. I can't create a secondary partition, because Fdisk says the entire disk is full. The BIOS is dated 11/11/92, which is before LBA was a thing. There's no reliable source for a BIOS update. I did find an Opti 486 BIOS on the Russian guy's site, but no date on it, no certainty it will even work in the MB. The 472.5MB is already >20x larger than the MFM slug it had, and much faster too.

It's always something...
 
PeterNC said:
Try a BIOS overlay.
Click to expand...

The controller is a DTC2278 which has one that does not appear to be like the Ontrack Disk Mangler, which I hate. I think the only catch is, I'll have to fdisk and format the drive on another system first. There's a catch-22. This overlay depends on having the full cylinder count in the BIOS, which I have, and it loads a driver from the config.sys, hence the need to format it elsewhere. That's why I have so many "mules" around, systems to service another system's drives. I plan to try that next.
 
mediasponge said:
The controller is a DTC2278 which has one that does not appear to be like the Ontrack Disk Mangler, which I hate. I think the only catch is, I'll have to fdisk and format the drive on another system first. There's a catch-22. This overlay depends on having the full cylinder count in the BIOS, which I have, and it loads a driver from the config.sys, hence the need to format it elsewhere. That's why I have so many "mules" around, systems to service another system's drives. I plan to try that next.
Click to expand...

I am having the same problem on a 386 right now.
A 2GB partition created by DOS6.22 on a late 486 with LBA works without any problems in this 486. It is a 2.1GB disk and I installed DOS to the only primary parition on this disk (2GB). Partition created+formatted with 6.22's fdisk/format.

Back in that 386: As soon as I try to access data that is beyond 504MB limit it fails on that. I did some investigation, defrag and swapping the drive between 386 and 486 before I understood what is happening there.

If you find a disk with 16 heads instead you will have the full 504MB instread of ~470 with 15 heads. If you give your BIOS 16heads, in fact there are only 15 heads in you disk, you will also get problems as soon he wants to access something on last head.

//edit:
Will ontrack disk manager help to get for example a 6,4GB or a 8GB drive working? One of these would be so nice in a 386.
 
My BIOS doesn't really do autodetect. It pretends, but only if it can physically access the drive. It came up with the same 13328-15-63 I got off the drive label. The driver for the VLB card only seems to let the BIOS access the disk using the 32 bits on the VLB, nothing more. I created a 2GB primary, active partition using another system and Paragon Partition Manager from the F4UBCD. The Opti 486 will boot from this, but it can't see any other partitions I created. I tried two more primary partitions, I also tried an extended with 2 logical partitions, but neither one was visible. The 486 system FDISK still thinks there's only 472MB total. DOS' DIR command thinks the disk is 2GB, but this would also likely fail once going past 472MB. The disk overlay looks like the only way. In that mode, the translation of CHS will let me put in 833-240-63. I'll still need 3x 2GB partitions, but the silly BIOS should see them, because the cylinder count is pretending to be < 1024. An overlay is fine until you need to remove it, which won't be an issue in this case.
 
mediasponge said:
I think the only catch is, I'll have to fdisk and format the drive on another system first.
Click to expand...
Simply put -- that will not work.

stecdose said:
I am having the same problem on a 386 right now.
A 2GB partition created by DOS6.22 on a late 486 with LBA works without any problems in this 486...
Back in that 386: As soon as I try to access data that is beyond 504MB limit it fails on that.
Click to expand...
... as expected.


stecdose said:
Will ontrack disk manager help to get for example a 6,4GB or a 8GB drive working? One of these would be so nice in a 386.
Click to expand...
It should.

mediasponge said:
The disk overlay looks like the only way.
Click to expand...
Agreed...
 
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