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ISA Hard Drive controllers

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First post, by Stojke

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What are the best hard drive controllers for 486/386 computers with out ATA/SCSI connectors?

Ive bought this model motherboard: http://www.ebay.com/itm/UM486-UM486SX-Vintage … y-/370602758586

And it does not have ATA/SCSI controllers.

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Reply 1 of 63, by elianda

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I guess fibre channel, but you need some pci board for this.

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Reply 3 of 63, by luckybob

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my personal favorite is the adaptec 1542C. Its cheap, common and basically the easiest to use scsi card for ISA you can expect to get. I've heard it will read from floppy drives at 2x speed but I never cared to test it out.

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Reply 4 of 63, by Stojke

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I bought some SCSI ISA controllers a few days ago, will check them out when they arrive. I think some are Adaptec.

Also, yesterday on the flea market i found some long ISA 16bit controller with a lot of chips and Zilog CPU. Had an IDE and Floppy connectors, didn't buy it, now i regret it 😀

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Reply 5 of 63, by luckybob

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there were a LOT of different 1542's. The first revisions had a hard drive limit of 512mb, but that was fixed with a bios update. (on the actual card) That said, the revision C is probably the best isa scsi card made for the money.

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Reply 6 of 63, by Stojke

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Oh i see. Well i will know once they arrive.

Can you tell me about high end controllers? And those that were special/rare etc.

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Reply 7 of 63, by fillosaurus

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I had several 1542 models; somewhere around here I think I still have a non-functional A; then I had a B and 2 CF, right now one remaining CF which is used in my VLB/SCSI 486.

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Reply 8 of 63, by keropi

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I have this 1522? card, is it any good?

SCSIISA_zpsba61c6dd.jpg

Last edited by keropi on 2013-06-19, 07:51. Edited 1 time in total.

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Reply 9 of 63, by luckybob

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that's the first revision. the first revision card has that many jumpers, there is nothing wrong with it, but you might have to flash the card's bios to allow for hard drives over 512mb. That and it's not plug-and-play like the revision C. As far as I can tell, all revisions will have the same performance, its just pnp & hard drive limit that are the major differences.

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Reply 10 of 63, by Stojke

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What is the maximum size these support? And also:

Can you tell me about high end controllers? And those that were special/rare etc.

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Reply 11 of 63, by fillosaurus

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As far as I know, Adaptec 1542 B/C/CF are some of the best ISA SCSI controllers. Anything with better performance will not be ISA.

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Reply 12 of 63, by luckybob

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The card pictured has a default hard drive size limit of ~512mb. If you flash its bios the limit is the same as all other isa cards. 8.4gb.

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Reply 14 of 63, by keropi

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@luckybob:
are you talking about the 1522a I posted? if yes, do you know where to get this bios update?

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Reply 16 of 63, by luckybob

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keropi wrote:

@luckybob:
are you talking about the 1522a I posted? if yes, do you know where to get this bios update?

yes. One of the best things about adaptec, they still have drivers and bioses for even the old stuff! http://www.adaptec.com/en-us/downloads/bios_f … n=aha-1520.html

you would need a programmer to do the flashing if memory is correct.

Stojke wrote:

I see. What are the technical reasons for this limit?

every bit of information you could want about hard drive sizes:
http://www.pcguide.com/ref/hdd/bios/size.htm

It is a mistake to think you can solve any major problems just with potatoes.

Reply 17 of 63, by Jepael

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Stojke wrote:

I see. What are the technical reasons for this limit?

The old CHS addressing method that was present in any disk BIOS call, so all things had to be compatible. Hard disks have 512-byte logical sectors, and are addressed with limits of 1024 cylinders, 16 heads and 63 sectors. 512*1024*16*63 is approximately 504MiB or 528MB.

The 16 heads was IDE/ATA limit, while 1024 cylinders is a BIOS limit. Newer, larger hard drives physically expanded the cylinders above 1024 but BIOS limits does not allow this so newer BIOSes do a geometry translation and instead expands logically the 16 heads to 256, the new BIOS limit being 512*1024*256*63 or about 8 gigs. Still compatible with old BIOS addressing.

(and to overcome that ~8gig limit linear LBA addressing method is used in even newer bioses with enhanced disk IO calls)

Plus, were there a lot of hard drives over 512MB anyway when we had early ISA only 486 motherboards.

Reply 18 of 63, by GL1zdA

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It seem that there are problems with SCSI controllers if you want to use Windows 3.x:

Windows FAQ wrote:
4.2.3. Selecting a hard disk ----------------------------- For best Windows performance, you want a WD-compatible disk contro […]
Show full quote

4.2.3. Selecting a hard disk
-----------------------------
For best Windows performance, you want a WD-compatible disk controller. As
most SCSI controllers (such as the excellent Adaptec 1542B and 1740) are
not WD-compatible, they can not use Windows' FastDisk 32-bit disk access
facility. Worse yet, you may need to double-buffer your SCSI drive with
SmartDrive, further degrading performance.

The best bet for Windows 3.1 and future Windows NT performance is a high-
speed IDE drive (all of which are WD-compatible). The controllers are
inexpensive (and built into many motherboards), and the new drives are
quite fast. IDE drives tend to be smaller, however, than their SCSI and
ESDI counterparts, ranging from 40 MB up to about 500 MB (SCSI and ESDI
drives currently on the market range from 300 MB to over 2 GB).

The final option is to use an ESDI drive; these drives are usually
identical to their SCSI counterparts, but with different interface
electronics. As long as you don't use a controller with a custom BIOS
(such as the WD-1009), you can use Windows' 32-bit disk access for better
performance. While ESDI is generally somewhat slower than SCSI, the 32-bit
access capability far outweighs that difference.

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Reply 19 of 63, by luckybob

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if the "WD" means WESTERN DIGITAL as its the only WD computer acronym that I know. then you can just ignore that. Some (early) western digital scsi adapters would only work with western digital hard drives. But this was bios only, if you update the bios any restrictions like this are removed. The Western digital ST01 & ST02 are most notable for this.

read more about windows and how it works with disk caching and smart drive here: http://support.microsoft.com/kb/83325

It is a mistake to think you can solve any major problems just with potatoes.