Routine computer maintenance.

[John Rumm]

Sure it was not a VESA rather than EISA? (i.e. a fast local bus extension for EISA systems that predated the introduction of PCI)

[Jethro_uk]

IIRC VESA was a *video* standard. EISA was an extension to the ISA spec (it used dual level connectors in the board) which allowed an EISA slot to carry either a normal ISA card, or a fully compliant EISA card, which needed to be configured in the BIOS. It was quite elegant, and backwardly compatible too.

[John Rumm]

VESA is/was a video standard - but also a bus extension standard. It added a third level connector on the board at the other end from the E/ISA slot(s)

Yup EISA came in with the 286 PC-AT - basically adding the extra connector beside the original ISA slot. It was still notionally limited to about 8MHz bus speed (although some BIOSes allowed you to push it a bit) with the same crippled edge triggered interrupt mechanism of ISA. Hence it was becoming a serious bottleneck for anything needing fast CPU / DMA access - especially video cards. Hence why VESA got involved with their own local bus to enable fast CPU to video card communications that were not limited by the ISA bus speeds. (IBM were countering with MCA at the time, and we know how well that went down!)

It just seems a little odd however going to the effort of describing a

486 machine as being "EISA" - since by that time everything had been EISA for a long time (i.e. 8 bit only slots had pretty much vanished by then) - and many fast machines of the day were sporting some form of additional "local bus". (the VESA bus was also quite closely based on the native 486 bus standard)

Some pictures of the VESAbus:

[Bob Eager]

Some IBM PS/2s had them too. The 55SX for a start.

[Vir Campestris]

You sure about all that? Because IIRC EISA only ever appeared on a few servers, had a config setting per interrupt to go level triggered, and never took off on desktops because PCI came along.

That Acer machine probably had some of my code in it - we (ICL) did deals with Acer, and someof the bugfixes were fed back into their products.

Andy

[Bob Eager]

Sorry, John, but that wasn't EISA. It was just known as 16 bit slots for a while until someone invented the term ISA to describe both the 8 and 16 bit slots - '8 bit ISA' and '16 bit ISA' if you like. The 16 bit slots appeared firts in the PC/AT around 1984.

EISA was a (mainly server only) much later (1988) architecture, produced to compete with MCA, which was IBM proprietary. MCA had level triggered interrupts (hence IRQ sharing) as well as a wider bus, some clever tricks to use the address bus to widen the data bus, semi automatic 'plug and play', etc. EISA had most of that, for the rest of the industry. It didn't last long partly due to the restricted market, so not many cards were made.

No - see above. EISA machines were fairly rare, so the effort *was* worth it!

[The Natural Philosopher]

Not sure your memory IS correct..there was ISA and then a enhanced ISA - fairly sure we sold Ethernet cards with that for a year or two - and then as you say PCI came along.

Mmm. the truth is somewhere between our memories it seems. It was a bit more common than you say, but less common than I remembered..

[John Rumm]

Perhaps we are talking about different things, but I have always considered ISA the original 6/8MHz 8 bit bus as per the IBM PC and PC-XT, and the Extended (E)ISA as the 16 bit version with the extra slot introduced with the PC-AT...

Ah ok, done some hunting about, EISA does indeed get used more than one way. My apologies... Seems the one you are describing is a later thing - contemporary with (or just before) VESA bus, and more commonly found in servers.

In fact thinking about it, I must have used a system based on it at some point since I recall using a configuration utility to configure expansion cards on it.

[John Rumm]

Yup, fairy snuff - I think I am remembering EISA being used (perhaps incorrectly, or unofficially) from the mid 80's. So for the purposes of this discussion, ignore me ;-)

[Vir Campestris]

Major brownie points there for actually admitting to a mistake. We're all here to learn.

No, scratch that last. Some of us are here to learn, others just for the arguments :)

Andy

[Grimly Curmudgeon]

I was a bit pissed off at having spent some serious wedge (for me at tht time) on an EISA sound card, which was superceded very shortly afterwards by the PCI version and by the makers dropping virtuall all support for the older ones within another couple of years. I still have it, it still sounds great, but using it means I have to keep an ancient motherboard up and running. If I'd known about PCI taking over the world at the time, I'd have waited a bit, and my PCI version would likely still be running easily enough (voltage variations allowed for, of course).