Upto 10Mhz for sure, 8Mhz being very common and where the turbo button comes from. Turbo will reduce the clock down to 4.77Mhz exactly matching the IBM PC and XT.

Mine is an 8Mhz even has the rom slots for Basic (though didn't come with them)

Up to 10 MHz, usually what you'll want to look for is something in an IBM PC XT style case with the elongated case badge indent in the front, or one of those DTK Chassis since DTK made a lot of "AT Style" XT Clone computers. They turn up on ebay pretty frequently. You'll want to be careful though because people often upgraded these to 286/386/486 or even some were made as a 286/386 based system (even seen at least 1 486 in the last 20 years), so getting gut shots would be a good idea.

Most of these would be "Turbo XTs" with CPU in the 6MHz-10MHz clock speed range.

Only means exclusive of. The presence of a turbo button defies the notion of only. A board can run atb6,8,10mhz... But not 4.77mhz.

It wouldn't be 100% IBM compatible if it didn't run optionally at 4.77mhz. If you throw that out then you get single frequency machines using 8088 cpus at various clocks. From as low as 3.5Mhz (Sanyo 1000??) upto 10Mhz. They however were DOS compatible but not PC, as frequency matching was the easy part of being PC compatible.

Some also had no turbo button but did have keyboard shortcuts (Compaq IIRC) and of course if you didn't connect the turbo button then it would run at its higher clock.

kant explain wrote on 2023-11-29, 20:38:

Only means exclusive of. The presence of a turbo button defies the notion of only. A board can run atb6,8,10mhz... But not 4.77mhz.

I get your question and I'm wondering if the issue is that the board inevitably has a 14.31818 MHz oscillator and the 8284 chip anyway, so it wouldn't make any sense not to offer a turbo button and use them, even if the turbo speed is higher (30 MHz or 24 MHz oscillator).

There's plenty of Turbo XTs without Turbo button, but many of them can be switched to de-turbo using some key combination or an utility, see eg. Commodore PC 10-III/20-III.

But as far as I know, the following can't be switched:
- IBM PS/2 model 30 - 8086 @ 8 MHz
- Amstrad PC1512 - 8086 @ 8 MHz
- Amstrad PC1640 - 8086 @ 8 MHz

Deano wrote on 2023-11-29, 21:03:

It wouldn't be 100% IBM compatible if it didn't run optionally at 4.77mhz.

IBM PS/2 model 30 obviously isn't 100% IBM compatible 🤣

But it should be noted that there's the 8086 inside, so even at 4.77 MHz it would be faster than the original IBM PC series of 8088 @ 4.77 MHz.

As long as we're straying from the beaten path, don't leave out the model 25. And the 286 vetsions of the model 30 and 25 also I think.

Oh did anyone mention the Lisa? Or the Victor Vicki? Shoot better not leave them out. They're close enough.

kant explain wrote on 2023-11-30, 05:22:

As long as we're straying from the beaten path, don't leave out the model 25. And the 286 vetsions of the model 30 and 25 also I think.

8086 models belong in the Turbo XT category.
Those with 286, however, are AT-class, therefore off topic.

Oh did anyone mention the Lisa? Or the Victor Vicki? Shoot better not leave them out. They're close enough.

Lisa has 68000, nothing to do with PC.

Edit: Posting about differences between XTs and AT removed.
It's the OP's thread, after all. If it's not wanted, then I do respect that.

Yep. A lot of off topic stuff found it's way to the thread.

Jo22 wrote on 2023-11-30, 06:37:

Edit: Posting about differences between XTs and AT removed.
It's the OP's thread, after all. If it's not wanted, then I do respect that.

No worries. Have a ball. Everyone else is mucking it up:)