486 + CD ROM Drive

[TheCorm]

I have someone with a v old Compaq 486DX 25mhz, it has about 6 ISA slots and an astonishing 8 simm slots. I tried installing some old simms but the board would not have them.

The problem I was then having was that it wouldn't recognise the CD ROM drive, am I right in thinking that the cd drive I have is only compatible backwards to PIO 3 and the 486 has an older interface?

OS is Win95.

Corm

 

[Shack70]

It should work if the CD is ok. Did you add the CD-Rom to the Bios setting? Are the slave/master setting correct?

 

[TheCorm]

The slave/master jumper was positioned correctly but there was not obvious way to get into the bios. I'm not sure what bios it's running...how do I access it?

cheers,

Corm

 

[MadRat]

Try F11 at startup.

 

[Dan]

You probably need to load DOS drivers for the CD-ROM.

 

[bacillus]

if the system is that old, maybe the cd drive connects via the soundcard.
or are you saying that the drive is not seen in dos?
for compaq F10 usually gets you into bios!

 

[Soccerman]

if you don't know, you have to install SIMMs in PAIRS.. the RAM size I think has to be the same (though don't quote me on that).

 

[Bleep]

soccerman is correct.
SIMMS have to be in pairs and they have to have the same capacity ie 16 meg simms together and in slots next to each other.
Bleep

 

[GD695372]

SIMMs don't have to be in pairs. This is only in systems with a 32-bit bus. The 486 has a 16-bit bus, and therefore should work just fine without them in pairs. Although I have seen some cases where they have ot be arranged in descending capacity from bank 0 on up.(weird huh?)

On a completely unrelated note, DIMMs ROCK!!!

No offense, just an excerpt form an old MCSE study guide.

 

[BA]

If there are 8 slots, and it's a 486, those are most likely 30-pin simms, in which case they should be installed in banks of 4. If they are 72, GD is right, you only need one at a time in a 486

 

[DaddyG]

You got good answers to your memory issues, noe for the CD-ROM. The BIOS will not autodetect it. Infact, if you try it will probably lock up. The cd-rom is set up as normal, master or slave but the BIOS detect is set to NONE. The DOS driver, loaded thru config.sys and MSCDEX loaded thru Autoexec.bat will find the CD-ROM. I wouldn't try anything faster than about 8X with this setup.

 

[TheCorm]

Getting hold of an 8x cd rom is easier said than done, I have now been able to get hold of a 100mhz DX4 which should be better, it uses the old 30 pin simms which is weird since the 25mhz used 72 pin simms.

Cheers for the help there, lot's of useful stuff - didn't know that about installing unpaired simms in old 486's.

 

[Vincent]

You can get some 8x CDROM drives from Computer Geeks.

I've got a 486DX-33 with a Promise EIDEPro (the motherboard doesn't have an IDE controller), and the CDROM doesn't detect in the BIOS. When Linux loads, though, it recognizes the CDROM and everything works fine.

I've been looking for some 4mb 30-pin SIMMs to upgrade the memory, but they're hard to find these days.

 

[BA]

If you're not using any DOS programs, you don't really even need the DOS drivers for it. Win95 should detect it just fine.

And 4mb 30-pins, good luck. I've got 4, but you ain't getting them.

 

[DaddyG]

BA, WIN95 will never detect the CD-ROM if he can't first access the CD-ROM. WIN95 boot disks do not include CD-ROM support.

 

[MadRat]

True statement.

 

[Soccerman]

I have 4 4meg 30 pin SIMMS on my 486, and I'm pretty sure I can run with 'only' two of them installed.. I don't remember what I had it at before I put those 4 meg SIMMS in.

I also thought you still had to put two SIMMS in when upgrading 72 pin SIMMS.. after all, a DIMM is just a two SIMMs on one slot (two banks a slot). hmm.. or not, because you CAN have only one bank occupied.. oh well.

 

[TheCorm]

With the first 486, the memory are all simms. The CD rom drive will just not detect. I know have hold of another system, a DX4 100mhz, this one has 30 pin simms, and I think the seperate ISA I/O controller is knackered and it won't initialize or detect either the 48x CD ROM, 540mb HD or 1080 HD.

Any other ideas?

Corm

 

[BA]

Well, I personally have never installed 95 off a CD, so. I always just copy all the cabs and setup over to the hard drive on another computer, then install the HD and install.

 

[shawnmos]

30pin ram must be installed in pairs of 4 or it won't boot. 72pin ram only needs one since the processor is 16bit. In the bios put the proper settings for the hard drive(master) and leave the cd-rom(slave) disabled(unless there happens to be a setting for cd-rom). If the hard drive settings are correct it should boot right off the ISA I/O controller. If it won't boot it could be the drive is not formated or doesn't have system files. Boot off the floppy and run fdisk. It should detect it. If it doesn't then the I/O controller is probably bad. If your installing off the cd get a hold of a win98 bootdisk if you can and boot with cd-rom support. If you can you should be able to download drivers that would fit on a disk somewhere.

BTW 30pin ram isn't that hard to find. I just bought 8 4MB simms off someone on the forums for $25 I think.

 

[shawnmos]

I forgot to add that if it only lets you use up to 500MB then you will need the special boot software that lets you use larger drives. Personally I'd rather use scsi for a 486 system. It is much faster then standard IDE and the SCSI card's BIOS autodetects the drive correctly. I have an old 486 system with an AMD 5x86 133 o/c to 150MHz with a SCSI 2GB hard drive, an IDE 16x cd-rom and 32MB ram. Not as slow as you'd think. Anyway the cd-rom is much faster then it would be if it were on the same cable with an IDE hard drive because they can't be read at the same time which really kills proformance. Oh if you need any 486 parts just ask cause I got a lot of old junk laying around.

 

[Vincent]

shawnmos, do you have any 4MB 30-pin SIMMs lying around? I've found some at the local used computer parts store, but they want something like $30 for four of them. If I were to spend that much money, I'd rather by more memory for my main system.

Some old ISA IDE controllers are so old that they don't support ATAPI devices like CDROM drives. CDROM drives weren't widely available when some of these IDE controllers were produced. This is the same reason why some of these controllers won't support large hard drives.

 

[MadRat]

A "used" PC parts store!?! Never. Go to the swap meets!

 

[esung]

both 486SX/DX uses 32bit bus for RAM, while 386DX uses 32bit bus, 386SX uses 16bit bus.

there's might be one way to see if the IDE controller is the EIDE or the standard IDE: check how many connectors are there. The old IDE only has one single channel that supports 2 drives. the newer EIDE will have 2 channel that supports HD and CDROMs.

 

[TheCorm]

Well in the end I got it to detect the old 1080mb hard drive, i think the 540mb one is knackered but i couldn't get the cd drive working. I then came up with the very same idea as someone mentioned to copy the cabs and whatnot over but as the network is running ME, it would recognise the 1080mb hard drive as it was FAT or FAT16 I think, definately not FAT32 anyhoo.

So now I have decided to get a few new bits together and use the monitor from this one (as it's a fairly good 15" Dell) to build a new system.

So the old bits are up for grabs should anyone want them, I can't make a huge amount of use out of them. email me if you are in the UK and may want these.

Cheers for all the help.

Corm