They were willing little machines. A V30 of course was a nice bump. The ones I had kinda spoiled me, in that genuine XTs and low end ATs felt like watching paint dry after the Amstrads. I got mine at junk prices at start of 90s when "Hmm seems this PC thing ain't going away...." to play with, but had to leave them behind in a long distance move unfortunately.

I used to have a PC1512, years ago. It was a nifty machine, not without its flaws, but on the whole good. It already felt quite fast compared to an 8088.
PCem can emulate the machine. I modified the source to make the CPU clock faster, but the system test that occurs when you switch on ("Please wait..." screen) fails with a graphics error. I'm not sure if it's just the mods I made, or if that would happen on the real hardware with a mod.

I also have a 1512 with a V30 cpu but it feels to me slower than a classic V20/CGA system I have... sure you get the nice amstrad videomodes sometimes but to my understanding the way they implemented the graphics really slowed things down... sometimes I wish I had the 1640 with the proper paradise EGA chip 🤣

keropi wrote on 2023-03-09, 11:38:

I also have a 1512 with a V30 cpu but it feels to me slower than a classic V20/CGA system I have... sure you get the nice amstrad videomodes sometimes but to my understanding the way they implemented the graphics really slowed things down... sometimes I wish I had the 1640 with the proper paradise EGA chip 🤣

This is weird. Looking at schematic they use proper separate video ram https://www.ardent-tool.com/datasheets/NEC_uPD41264.pdf on its own bus https://www.manualslib.com/manual/859355/Amst … ?page=31#manual
No funny PCjr reusing main ram for video business here. Do you remember the details? does it have especially slow write speed to video ram?

rasz_pl wrote on 2023-03-09, 16:31:

This is weird. Looking at schematic they use proper separate video ram https://www.ardent-tool.com/datasheets/NEC_uPD41264.pdf on its own bus https://www.manualslib.com/manual/859355/Amst … ?page=31#manual
No funny PCjr reusing main ram for video business here. Do you remember the details? does it have especially slow write speed to video ram?

check this thread: https://forum.vcfed.org/index.php?threads/how … and-1640.75387/
it does feel to me slower than my 10mhz hyundai xt but maybe it's placebo/marginal - so take it with a grain of salt 😉

keropi wrote on 2023-03-09, 18:25:

check this thread: https://forum.vcfed.org/index.php?threads/how … and-1640.75387/

thank you
meanwhile I setup few auction side notifications and will hunt for cheap broken/non complete one to tinker with
If someone has broken one in central EU, or would like some mods done (ctrl-alt-rees described supply/CGA output) hit me up.

yeah it is a nice system to keep an eye out for - especially with the color monitor
but it certainly does not feel like a 8086 system to me , which is a shame but then again at this competitive price some things are to be expected
and let's not forget it's an Amstrad system after all 🤣

ah there it is https://www.seasip.info/AmstradXT/1512tech/section1.html "on-board 8 bit I/O and memory peripheral bus with a 4 MHz clock". Yep, BUS ASIC divides 24MHz clock into 8MHz for CPU and 4MHz for ISA bus. Doesnt appear to have any configuration pins for controlling waitstates, unless some are hidden behind multiple ground/supply pins or one of the "Do Not Use" reserved IO ports. Btw curiously POST port 80h is also "Do Not Use".
There is still hope if it can be pushed up to 12MHz CPU clock 😀 that would move ISA to 6MHz.