As far as I know, officially there are no 8088 or V20 CPUs that are rated higher than 10 MHz.
The fastest 'common' variation of turbo XTs is 9.54 MHz (double that of the original PC).
I do vaguely recall however that there were some 'factory-overclocked' XT clones of 12 or 12.5 MHz. But I can't name any brands or models, so I may be mistaken.

Edit:
Apparently this might be such a board: https://th99.bl4ckb0x.de/m/A-B/32279.htm

Scali wrote:

As far as I know, officially there are no 8088 or V20 CPUs that are rated higher than 10 MHz.

I've got some cheap V20s bought from an ebay Chinese seller that are rated for 16MHz. Of course I don't own anything that can go beyond 10MHz to try them, so I only know that they work at 10MHz.

But despite my doubts for these specific chips, it is a fact that NEC officially produced V20s rated higher than 10MHz. I never encountered a PC/XT using one at full speed though, maybe they were targeting different platforms?

Scali wrote:

As far as I know, officially there are no 8088 or V20 CPUs that are rated higher than 10 MHz.

There are HL variants of V20 and V30 rated up to 16MHz.

Good to know, thanks!

Kubik wrote:

Scali wrote:

As far as I know, officially there are no 8088 or V20 CPUs that are rated higher than 10 MHz.

There are HL variants of V20 and V30 rated up to 16MHz.

It seems you are right, here is the datasheet (I had only looked at the regular V20 before):
http://html.alldatasheet.com/html-pdf/162440/ … 08HG-10-22.html

The uDP70108HCZ-16 would be the 16 MHz version that is pin-compatible with a 8088.
There is also a 12.5 MHz version.

The V40 was used in some laptops. I had a sharp laptop with one. I don't remember it being any faster than a V30 based desktop, so I think the V40 was more a low power/cost saving option than a performance part. Any other Australian here remember the micron pc300 (I may have the name wrong, it's been a long time) - small form factor PC before SFF was a thing, 10MHz V30. What made is special and faster than most other XT class systems was the onboard EGA and SCSI also ran at 10MHz...

As for all the NEC Vxx stuff, Wiki covers it well: https://en.wikipedia.org/wiki/NEC_V20 😀
I recommend reading it, a lot of interesting stuff!

One of the most interesting of the NEC V series is the V33A. It can address up to 16MB like a 286. Unfortunately, I don't know that it was ever used in a PC. It's not a 286 clone, and I don't think it has a protected mode.

BTW, according to that wiki page, the Vadem VG330 (a portable?) has a V30MX running at 32MHZ!

Resurrecting this thread...

I've seen a catalog from a spanish manufacturer that offered a 15MHz PC/XT, that was dated on 1989. Also, I've seen that Nec offered both V20HL and V30HL rated at 16MHz on 40 pin DIP package. Does anyone knows when did Nec launched those CPUs (the datasheet I've found is dated in 1995)?

BTW, that catalog stated that their PC/XTs uses a 8088-2 CPU... it seems that their CPUs were overclocked (instead of using a 15 MHz rated CPU). It would be interesting to know what mainboard was used, if it was modified or supported 15 MHz via jumpers, and if the ISA bus was running out of specs when overclocked.

If anyone is still interested in this my Tandy 1000 SL is now running at 16Mhz with a NEC V30. Speed is extremely interesting, should be in line with well tuned 10Mhz 286 systems, performance wise.

carlostex wrote on 2020-01-03, 19:41:

...my Tandy 1000 SL is now running at 16Mhz with a NEC V30.

Sweet! Now it's an even BETTER PCJr than the PCJr.

AlaricD wrote on 2020-01-10, 17:41:

carlostex wrote on 2020-01-03, 19:41:

...my Tandy 1000 SL is now running at 16Mhz with a NEC V30.

Sweet! Now it's an even BETTER PCJr than the PCJr.

Tandys were always the PCJr done right.