Maximum PC

no i meant on thwe thing Is aid earlier

The AT specifications? It's all on page 35 of Scott Mueller's Upgrading and repairing PCs.

In case you don't have the book here's what it says:


Table 2.3 Differences Between PC/XT and AT Systems

System Attributes: (8-bit) PC/XT Type

Supported Processors: All x86 or x88
Processor Modes: Real
Software Supported: 16-bit Only
Bus Slot Width: 8-Bit
Slot Type: ISA only
Hardware Interrupts: 8 (6 Usable)
DMA Channels: 4 (3 Usable)
Maximum RAM: 1MB
Floppy Controller Speed: 250Kbps
Standard Boot Drive: 360K or 720K
Keyboard Interface: Unidirectional
CMOS: None Standard
Serial Port UART: 8250B


System Attributes: (16/32/64-Bit) AT Type

Supported Processors: 286 or Higher
Processor Modes: Real/Protected/Virtual Real
Software Supported: 16 or 32-bit
Bus Slot Width: 16/32/64-Bit
Slot Type: ISA, EISA, MCA, PCMCIA, CardBus, ExpressCard, VESA Local Bus, PCI, PCI Express, AGP
Hardware Interrupts: 16 (11 Usable)
DMA Channels: 8 (7 Usable)
Maximum RAM: 16MB/4GB or More
Floppy Controller Speed: 250/300/500/1,000Kbps
Standard Boot Drive: 1.2MB/1.44MB/2.88MB
Keyboard Interface: BiDirectional
CMOS: MC146818 Compatible
Serial Port UART: 16450/16550A or Greater