Many later Tandy 1000s (including my 1000RL) allow for up to 768K to be installed on the motherboard, but only up to 640K is addressable to DOS. The memory above 640K is permanently reserved for use as video RAM, even when the video is not using all of that extra 128K.
On the other hand, my Ampro "Little Board/PC" provides three 256K SIMM sockets, and with the full 768K RAM installed, it does provide extra DOS-accessible RAM above 640K: up to 704K when you have its video controller in MDA mode, or up to 736K when it is in double-scan CGA mode (text mode resolution increased to 640x400 on an EGA-spec monitor, plus standard 320x200 and 640x200 graphics modes). It has a NEC V40 CPU at 7.16 MHz, intergrated serial, parallel, floppy, and SCSI hard drive controllers, and one 8-bit ISA slot. It has a socket for a proprietary NEC V-series math co-processor (not pin-compatible with the 8087) which was ultimately never released by NEC. It has a semi-high density floppy controller: it supports 1.2MB 5¼" drives, but only 720K 3½" drives, since the 1.44MB format hadn't been invented yet when it was introduced.
The Ampro is also the only PC I've seen with a functioning "System Request" key implemented in BIOS: pressing the SysReq key on your keyboard (a.k.a. Alt-Print Screen) at any time pops up its hardware configuration screen.