Guys, what would be the performance impact on the CPU when using an ISA SCSI controller instead of a PCI one? Since the conversation seems to be only about the PCI cards... I personally think no difference will be noticed, but I also want to ask whether somebody here tried to bother him/her-self with such a thought. Or even tried in practice.

Isa is a LOT slower. 16 bit isa has a theoretical maximum of 8MB/s. Pci caps at 132MB/s. Now if your hard drive is slower than 8mb/s you wont notice, but if you use a new drive, it will be a lot different.

Eh? Isn't it 16bit / 8bit = 2B x 8Mhz = 16MB/s ?

Not to say that most of us run the ISA bus higher than nominal, thus giving even 20MB/s?

sorry, typo. I ment to type 18, but in reality its more like 16 like you said. Still, 16mb/s is probably plenty for a 486, but remember it is SHARED between all isa devices.

Sound, serial, parallel, mouse, keyboard will all fight for bandwidth. (i'm assuming you arent doing something silly like using isa graphics when you have pci availible)

Go SCSI. Anything that lifts some of the burden off of the CPU is going to benefit your games tremendously and save/load times will be a lot snappier not only because of the faster rotational speed of the drive but also the increased bandwith SCSI provides over early implementations of IDE. Naturally, you'll be wanting to run it from a VL-Bus or PCI slot to keep your ISA slots free for other things that don't require the extra bandwith. As mentioned above, plugging a lot of bandwith hungry devices into the ISA bus is going to lead to bottlenecks.

The conversation is not only about PCI 😉
I'll have a PCI 486 and a VLB one, but I won't be able to do direct comparison, since the cars won't be the same (2842VLB and 2940PCI)

Actually I chose SCSI over compact flash to free the CPU of disk management 😉
I remember the old times when disk access froze everything else ...
On the other hand, disk access may be so fast on compact flash we can't feel the freeze ... mmm

sunaiac wrote:

The conversation is not only about PCI ;) I'll have a PCI 486 and a VLB one, but I won't be able to do direct comparison, since […]
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The conversation is not only about PCI 😉
I'll have a PCI 486 and a VLB one, but I won't be able to do direct comparison, since the cars won't be the same (2842VLB and 2940PCI)

Actually I chose SCSI over compact flash to free the CPU of disk management 😉
I remember the old times when disk access froze everything else ...
On the other hand, disk access may be so fast on compact flash we can't feel the freeze ... mmm

If the IDE controller is maxed out, it doesn't matter how fast the CF card can be accessed. Once you hit the ceiling, that's all you get so it doesn't make much sense to plug a fast drive into a slow controller.

The fastest 486 numbers I've seen are Feipoa's hotrod 5x86 rig. About 30MB/s from the HDD and around 57MB/s from RAM.

The World's Fastest 486

If we're talking 486 era, I've used a BusLogic BT-445s VLB w/ a WD Enterprise 2.17GB 7200-rpm drive for a while. My new 486 MoBo didn't like the card, though, something about a DMA conflict.

Next up I went with the SiiG VLB IDE-I/O w/ a 2.1GB Seagate drive, and that MoFu is FAAAAST! -- compared to the SCSI....contra-indicative but very, very true. I've got my 486 the way I want it, I guess as I haven't touched it since.

Now onto my "other" projects...

386
Socket4
Super7

..where are all those AT cases when I need them.

sunaiac wrote:

I have a very stupid question, but i can't seem to find a clear answer. I decided to go full SCSI on my 486s, and got myself sev […]
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I have a very stupid question, but i can't seem to find a clear answer.
I decided to go full SCSI on my 486s, and got myself several of those (same model, not at that price of course) : http://discountechnology.com/Seagate-ST318406 … CSI-Hard-Drives

I have adaptec cards, all in 50 pins, either 2940 PCI for the PCI 486 or 2842A VLB for the ... well VLB one.

I obviously have no troubles with the speed limitation at 20mb/s, but i'm puzzled about that LVD stuff.
It seems it should work with a lvd certified adapter. Could anyone point me an ebay listing with an adapter that is sure to work ? I have 68 and 50 pins wires, but since I also got the CD burners to plug, i'd prefer a HDD side adapter.

Thanks !

edit : there's a "Force Single Ended" jumper on the HDD if it can help.

So the time for me has come to start building my 486s ...
And with that come the first problems 😁

So here we are, I have the following setup :

HOT Shuttle 433
AMD DX5 WriteBack
S3 Trio in PCI1 IRQ9
Adaptect AHA2940U2W in PCI4 (will not go in others, because of CPU cooler) IRQ11
All IDE disabled in the bios except the thing that looks fior IDE cards on PCI cause it can't be disabled

On the Adapted (ID7), I try to plug a 18GB LVD HDD (ID0, 50-68 pins adapter with active termination)) and a 50 pins CDROM (ID3).
Nothing works. CD alone, HDD alone, etc ... card does not detect any drives.
I think the best setup would be card --> cd (term off) --> hdd (with active termination adapter). But no setup works. I don't have a jumper on the "Force single ended" pins.

So where do I start ? (mini jumpers ordered and coming)
If I could at least get the CD recognized ... I tried just the CD on the last point of my SCSI cable with termination on, even that is not recognized by the card ...

I can go in card's bios. SCSI bios is enabled, CDROM bootable too.
any ideas ? I'd like this one to work before takling the VLB 😀

I have gotten the Adaptec 2940U2W card working on a HOT-433 before. Sometimes the cables connectors have gone bad without any physical sign of damage. Try several different cables. Try cable-terminated cables and non-terminated cables, whereby termination is enabled with the HDD/CD jumper. It is fuzzy in my mind, but I think the SCSI card had to be on the first or third PCI slot, while sometimes you need to remove the card, jumper clear CMOS, reinsert the card, and then it may work. The HOT-433 isn't the best motherboard for using SCSI PCI bus mastering.

You should not have to jumper anything on the HDD if you are using a SCSI terminated LVD cable, 68-pins. It will default to SCSI ID 0. Be sure to have termination on the adapter side set to automatic. This can be found in the SCSI BIOS options.

Try the same Adaptec card and HDD in a Pentium or newer computer to ensure everything is functional. I suspect a BIOS confussion issue, which is what swapping the card slots circumvents. There may be another BIOS setting messing with the card. I know I've got this working before, but it has been too long to remember the exact resolution.

I was expecting you, thanks for coming 😉
My problem is the card won't actually fit in other slots 😖 (CPU cooler)
I might have a good chance with the first slot, i'll see.
else I might get a 2940AU, it's shorter.
But the card seems to work. It could be in a situation where the card works until at least its bios but can't find drives because of bus mastering issues ?

Possibly so. I have even noted on a particular VIA Apollo Pro 266T dual Tualatin board that the 2940U2W would only work in the first 3 slots for whatever reason. The symptoms are exactly as you describe in that the card's BIOS comes up, but cannot find the drives. When I moved the card to slots 1-3, it found the drives. Yet on another brand VIA Apollo Pro 266T board, the 2940U2W worked in any slot.

While this may not be the solution to your problem, it is worth looking into. I think if you use a standard (small) 486 heatsink/fan, the 2940U2W will fit in the first slot of the HOT-433. I haven’t played with this in a while, so I may be wrong.

Which BIOS version are you using? There are 4 different onces for this board. I think you also need to leave Map IDE section unchanged, that is, map to ISA (not to PCI) and leave the INT stuff alone. You might also want to try leaving the IDE channel 1 & 2 ports enabled just for testing. It is possible that the BIOS is semi-releasing IRQ 14/15 for these ports and that the Adaptec is trying to use them instead of IRQ 9-12 (speculation).

I have never been a fan of the HOT-433 and found it to be pretty flakey/unpredictable.

Bios is AMI dated 10-10-94.
That motherboard is all I have as PCI 😖, couldnt find the biostar you have 😖
And I don't ant to do two VLBs.
I'll try swapping the card or using a 2940AU. I'll also try deactivating CDROM boot in the card's BIOS, some site says it (can) help.
Will keep you in touch.

PS : I don't remember seeing a way to "map" IDE, the BIOS said PCI everywhere.

sunaiac wrote:

Bios is AMI dated 10-10-94.

That is the AMI release date, not the BIOS programming date done by Shuttle HOT.

Your BIOS "date" will be one of these:

433AUE2A
433AUE23
433AUE33
433WIE10
433AIP16
433AUS26
433AUS2A
433AUS2C

Looking at a photo of the HOT-433, I don't see how you could not fit the Adaptec card into the first slot (closest to the SIMMs).
http://www.amoretro.de/2012/01/shuttle-hot-43 … otherboard.html

Mine is not the same, How come :??:

http://imageshack.us/photo/my-images/5/img1384.png/
http://imageshack.us/photo/my-images/708/img1480.png/

edit : seems mine is V4.0, slightly different.

Whenever refering to a HOT-433 v4, it is best to mention "v4", otherwise it is assumed version 1-3. v4 also has some SCSI bus mastering issues, but only really becomes a problem in W2K. For Win98, you will get the occasional confusion at boot, whereby the PCI bus or SCSI host controller gets hung up trying to find the boot device. It will cycle between SCSI CD-ROM and HDD for hours in mass confusion.

Sorry sir 😁

In my 'sperience, LVD and SE devices don't get along too good on the same chain. That may just be my anal retentive nature, but me thinks I've had that same problem in the past w/ Adaptec. I know in most of the server boards I've worked with from the 2940 era, you generally had an LVD bus and another separate SE bus.