Tweaker Finally Designs an AMD Slot A to Socket A Adapter After 23 Years – Computer – Geeks

When AMD switched from Slot A to Socket A in the early 2000s, back in the days of the Athlon Thunderbird, many trainers were hoping an adapter would be available. He never came, but a member of the community Auto 660 He wants to change that after 23 years.

With a slot-to-socket adapter, also known as a “slotket”, it was possible to put a new socket processor into the slot-in motherboard, which would have saved on buying a new motherboard. For Intel processors at that time, these adapters already existed, For example To place Celeron for Socket 370 into the Slot-1 motherboard. Despite optimistic reports between May and September of the year 2000, the production of such adapters for AMD processor sockets was too complex to be economically feasible at that time.

Slot A next to the Socket A processor. Source: CPU world

Auto660 began its slotket adapter design project by researching a suitable motherboard to see if the used AMD 751 and Via KX133 chipsets would work with Socket A processors. The Gigabyte 7IXE4 piqued his interest, as the Socket A motherboard shares many similarities with the 7IXE for slot A. It uses the same AMD751 chipset. Even in the bios references to the functions of the Slot A processors can be found. It is also verified that there are no significant differences between the signals used by the slot and socket Athlons.

The main hardware difference between slot and socket CPUs, in addition to the physical connection of course, was the use of a second interface transistor. Slot processors have what is called an open drain interface with one (0) transistor and one (1) pull-up resistor. For socket CPUs, AMD has switched to a push-pull interface with a transistor for both values. Its lower resistance allowed for faster switching, which enabled AMD to increase the front-side bus speed in its socket processors.

the Athlon processors “Thunderbird” They are the first Athlons without an external cache and thus use a socket again for the first time. However, all Socket A processors still have hardware for working with an open-drain interface, because some models with the name Athlon Classic were also supplied in slot form, in order to extend the life of this platform. It quickly turns out that only the Via KX133 chipset is unstable with Thunderbirds, so the plug is still being pulled from the Slot A platform.

So this compatibility was planned, and it is also evident from the manual for Epox’s Slot A motherboard with Via KX133 chipset. This manual mentions a bus speed of 133MHz, up from the standard 100MHz, but this was not usable in practice due to errors in the PCI/AGP dividers.

A notable detail is that the Gigabyte 7IXE4 motherboard uses the newer push-pull interface along with the older AMD751 chipset, which was previously considered a stumbling block to switch usage. This also differs from AMD’s approach, which used an open exchange interface with the Athlon Classic. With a custom bios, the motherboard works with almost all Socket A processors, indicating that there are no hardware limitations that prevent Slot A chipsets and Socket A processors from working together. This confirmed the possibility of a slotket adapter operating using a push-pull interface.

Now that the hardware aspects don’t seem to be a hurdle, the software is the main hurdle that still needs to be removed. Therefore, the bios for the motherboard must be modified. In particular, this concerns the SysPushPull parameter, which ensures that the push-pull interface is used instead of the open exchange interface. The search for the bits in the bios-rom that are exactly responsible for this continues.

Finally, auto660 has already designed a slotket adapter circuit board. The PCB is made up of six layers and follows AMD design guidelines for Socket A systems where possible. To be able to easily install a modern cooler – Athlons since then consumes about 80 watts – the fiend made mounting holes in Socket AM4. With battery dip switches on the left of the picture, multiplier, Vcore, and L2 cache size can be set. The connector on the top can be used in the future to enable Vcore and temperature reading.

PCB design for slotket adapter
PCB design for slotket adapter, with dipswitch outline on left and legend on right

Auto660 wants to produce the designed printed circuit board and hopes to be able to actually test the process in a few months. The progress of the project can be followed in the German forum Luxx deviceswhere a small but passionate community is keeping the legacy of Socket A CPUs alive.

slotket adapter for socket A on the motherboard Slot A.

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