• Please review our updated Terms and Rules here

486 VLB Motherboard - Adding Another Hard Drive

S

shan2752

Member
Joined
Nov 26, 2017
Messages
41
Location
Ohio, USA
Hello,

I have a Decpc lpx+ 486 with a motherboard that only has 1 IDE Port. I have a 525 MB hard drive as master and a 48x CD-ROM as slave. I want to add another hard drive for storage. What is the best way to accomplish this? I’d ideally like to add a CF solution but I’ve only ever seen these for IDE. Is adding a larger new SCSI hard drive via an ISA SCSI adaptor card an option? Any advice would be greatly appreciated. Thanks!
 
SCSI is an option but probably not cheap unless you already have the parts. There are SCSI to CF adapters but they aren't common.

Many sound cards have tertiary IDE channels. You can also add an ISA or VLB card with IDE (multi I/O controllers with IDE are common). You will need to make sure that the IDE channel can be configured as secondary so it does not conflict with your motherboard. And any overlapping ports (com/lpt/game) are disabled.

I would put the hard drives on your motherboard since that interface is probably VLB. And put the CD-ROM on your sound or I/O card.
 
Thanks for the suggestions! What size CF card do you use? One can expect a single 2 GB partition to work?
 
I have 2 GB CF cards in my XT machines that also have the XTIDE cards in them. The XTIDE cards have an extended BIOS that support large drives.

I have a 2GB in a 386, but that computer only uses it as a 512mb since that is the max size that BIOS can recognize. I'd try a 2GB card and see if your BIOS will work with it.
 
An SCSI card with its own BIOS will get around the 512MB limit on that 386 (using an SCSI drive of course).
 
If you want to go the SCSI route, you can get an ISA SCSI card and a SCSI2SD board. They're not cheap, but they're reliable, a lot more so than 25-30 year old SCSI drives. You can still buy crusty old SCSI drives from the usual fleabay, but for inflated prices and you're not guaranteed a working drive. The older 50 pin drives tend to fetch a premium, but you can use newer 68 pin drives with a passive adapter, since most ISA SCSI cards are 50 pin only.

SCSI has the benefit of usually having its own BIOS that doesn't have the int13h geometry limits, as well as being faster. While the disk transfer speeds generally aren't that much greater, a SCSI2SD board has virtually no seek time and SCSI devices don't burden the host CPU to do data transfers, so the system is overall much faster.
 
Thanks for all the help! I think I’m going to look into the SCSI solution. I presume the only method for increased drive size is to use the SCSI SD drive as a boot drive utilizing the cards bios? Or does the bios still come into play if used as a non-boot drive. Darn, this stuff is complex.
 
The SCSI controller won't care if you boot from the drive or not.

You can also increase maximum IDE drive size with a DDO (Dynamic Drive Overlay, e.g. EZ-Drive), or an add-on IDE BIOS like XTIDE Universal BIOS or Promise DriveMax.
 
The SCSI BIOS is going to be involved for any SCSI device attached to the SCSI bus, whether it be a hard drive, optical drive, scanner, etc. All of the same limits apply to all devices.

But you have additional limits in DOS. If you're not using the more modern FreeDOS that supports FAT32 partitions, you'll be stuck with FAT16 if you use MS-DOS 6.x with a maximum partition size of 2 GB. You can create as many partitions as letters in the alphabet, but it gets irritating finding stuff after 4 or 5.
 
I purchased and installed the SCSI2SD V5.2 with a NOS Adaptec AHA-1542CP adapter. Works great with a 2GB SD card. I had to switch jumpers as default port was 330-334. I have my PC midi card with MT-32 and SC-55 on 330. Thanks for sharing information about this great device!

Surprisingly, I noticed that Doom and Doom 2 both take significantly longer to boot from the SCSI SD card than from the IDE hard drive. Any reason for this?
 
Not sure why Doom is taking longer to load on SCSI2SD. While the throughput isn't going to be much higher due to SCSI bus limitations, seek times should be sub 1ms. I'd guess Doom is trying to access data in a way the SCSI2SD doesn't like.

It could potentially be something like a caching issue, not sure if SCSI2SD has a disk cache.
 
You must log in or register to reply here.
Back
Top